Academy of Pharmaceutical Sciences
- Authors: Walker, Roderick B
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184768 , vital:44270 , xlink:href="https://hdl.handle.net/10520/EJC-98c37d47c"
- Description: It is an honour and a pleasure to report on the activities of the Academy of Pharmaceutical Sciences since the PSSA AGM in 2016. The Academy of Pharmaceutical Sciences of the Pharmaceutical Society of South Africa (APSSA) held their 37th Annual Conference and 38th Annual General Meeting at the All African Congress on Pharmacology and Pharmacy. The conference was jointly organised by the Academy of Pharmaceutical Sciences of South Africa (APSSA), the South African Society for Basic and Clinical Pharmacology (SASBCP) on behalf of Pharmacology for Africa (Pharfa) and the Toxicology Society of South Africa (ToxSA). The annual APSSA conference was hosted by the Department of Pharmaceutical Sciences, Tshwane University of Technology under the leadership of Dr Ilze Vermaak and was held from 5-8 October 2016 at Misty Hills Conference Centre, situated close to the Cradle of Humankind.
- Full Text:
- Date Issued: 2017
- Authors: Walker, Roderick B
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184768 , vital:44270 , xlink:href="https://hdl.handle.net/10520/EJC-98c37d47c"
- Description: It is an honour and a pleasure to report on the activities of the Academy of Pharmaceutical Sciences since the PSSA AGM in 2016. The Academy of Pharmaceutical Sciences of the Pharmaceutical Society of South Africa (APSSA) held their 37th Annual Conference and 38th Annual General Meeting at the All African Congress on Pharmacology and Pharmacy. The conference was jointly organised by the Academy of Pharmaceutical Sciences of South Africa (APSSA), the South African Society for Basic and Clinical Pharmacology (SASBCP) on behalf of Pharmacology for Africa (Pharfa) and the Toxicology Society of South Africa (ToxSA). The annual APSSA conference was hosted by the Department of Pharmaceutical Sciences, Tshwane University of Technology under the leadership of Dr Ilze Vermaak and was held from 5-8 October 2016 at Misty Hills Conference Centre, situated close to the Cradle of Humankind.
- Full Text:
- Date Issued: 2017
Sensitive high-performance liquid chromatographic determination of cyclizine and its demethylated metabolite, norcyclizine, in biological fluids using coulometric detection
- Walker, Roderick B, Kanfer, Isadore
- Authors: Walker, Roderick B , Kanfer, Isadore
- Date: 1995
- Language: English
- Type: text , Article
- Identifier: vital:6452 , http://hdl.handle.net/10962/d1006640 , http://dx.doi.org/10.1016/0378-4347(95)00202-T
- Description: An accurate, sensitive, selective and reproducible high-performance liquid chromatographic method with coulometric detection for the determination of cyclizine and its inactive demethylated metabolite, norcyclizine, in biological fluids has been developed. The drugs were separated using a custom packed reversed-phase C18 analytical column and phosphate buffer (0.05 M, pH 3)-acetonitrile (7:3) as mobile phase. The dual electrode coulometric detector was operated in the "oxidative-screen" mode with the upstream electrode (detector 1) set at 0.55 V and the downstream electrode (detector 2) set at 0.90 V. Serum and urine samples were prepared for analysis by solid-phase extraction, followed by a simple phase-separation step. The limit of quantitation was 1 ng/ml for both cyclizine and norcyclizine in serum and urine.
- Full Text:
- Date Issued: 1995
- Authors: Walker, Roderick B , Kanfer, Isadore
- Date: 1995
- Language: English
- Type: text , Article
- Identifier: vital:6452 , http://hdl.handle.net/10962/d1006640 , http://dx.doi.org/10.1016/0378-4347(95)00202-T
- Description: An accurate, sensitive, selective and reproducible high-performance liquid chromatographic method with coulometric detection for the determination of cyclizine and its inactive demethylated metabolite, norcyclizine, in biological fluids has been developed. The drugs were separated using a custom packed reversed-phase C18 analytical column and phosphate buffer (0.05 M, pH 3)-acetonitrile (7:3) as mobile phase. The dual electrode coulometric detector was operated in the "oxidative-screen" mode with the upstream electrode (detector 1) set at 0.55 V and the downstream electrode (detector 2) set at 0.90 V. Serum and urine samples were prepared for analysis by solid-phase extraction, followed by a simple phase-separation step. The limit of quantitation was 1 ng/ml for both cyclizine and norcyclizine in serum and urine.
- Full Text:
- Date Issued: 1995
Cyanide-induced free radical production and lipid peroxidation in rat brain homogenate is reduced by aspirin
- Daya, Santylal, Walker, Roderick B, Anoopkumar-Dukie, Shailendra
- Authors: Daya, Santylal , Walker, Roderick B , Anoopkumar-Dukie, Shailendra
- Date: 2000
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184346 , vital:44210 , xlink:href="https://doi.org/10.1007/BF02674529"
- Description: The neuroprotective properties of aspirin were investigated using cyanide-induced neurotoxicity as model. Cyanide, a known neurotoxic agent significantly increased lipid peroxidation and superoxide anion levels in rat brain homogenate in a concentration-dependent manner (0.25–1.0 mM). When homogenate, containing 1.0 mM KCN was cotreated with aspirin (1.0 mM) there was a significant decrease in lipid peroxidation. Aspirin (0.5 mM and 1.0 mM) also significantly reduced KCN-induced superoxide anion generation. The results of the present report therefore indicate a neuroprotective role for aspirin.
- Full Text:
- Date Issued: 2000
- Authors: Daya, Santylal , Walker, Roderick B , Anoopkumar-Dukie, Shailendra
- Date: 2000
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184346 , vital:44210 , xlink:href="https://doi.org/10.1007/BF02674529"
- Description: The neuroprotective properties of aspirin were investigated using cyanide-induced neurotoxicity as model. Cyanide, a known neurotoxic agent significantly increased lipid peroxidation and superoxide anion levels in rat brain homogenate in a concentration-dependent manner (0.25–1.0 mM). When homogenate, containing 1.0 mM KCN was cotreated with aspirin (1.0 mM) there was a significant decrease in lipid peroxidation. Aspirin (0.5 mM and 1.0 mM) also significantly reduced KCN-induced superoxide anion generation. The results of the present report therefore indicate a neuroprotective role for aspirin.
- Full Text:
- Date Issued: 2000
Design, evaluation and optimization of taste masked clarithromycin powder
- Ntemi, Pascal V, Walker, Roderick B, Khamanga, Sandile M
- Authors: Ntemi, Pascal V , Walker, Roderick B , Khamanga, Sandile M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183503 , vital:44001 , xlink:href="https://doi.org/10.1691/ph.2019.8116"
- Description: Clarithromycin (CLA) is an extremely bitter macrolide antibiotic used to treat paediatric and adult infections. The bitter taste affects patient adherence and may compromise therapy. This research developed a taste masked CLA resinate using Indion® 234, a weak acidic cation exchange resin. The factors affecting formation of the CLA-resin complex were assessed. Design of experiments was used to optimize response while evaluating input variables such as temperature, CLA-resin ratio,stirring time and pH. CLA loading efficiency was determined spectrophotometrically and CLA release using USP Apparatus II. Differential Scanning Calorimetry (DSC), Scanning Electron Microscop (SEM), Fourier Transform Infrared (FT-IR) Spectroscopy and X-ray Diffraction (XRD) were used to confirm complex formation. A spectrophotometric method was used to assess taste evaluation. The optimum CLA-resin ratio, temperature, and stirring time were 1:4, 80 °C, 3 hours, respectively, at pH 8. Characterization techniques revealed that CLA was crystalline and the complex amorphous in nature. FT-IR spectra of resinate revealed the absence of resonance due to the tertiary amine functional group that is responsible for the bitter taste of CLA. CLA was stable in simulated salivary fluid and was released within 3 hours in gastric fluid. All CLAresin batches revealed complete taste masking. Taste analysis highlighted the improvement of taste masking properties of the resinate as the CLA to resin ratio, increased.
- Full Text:
- Date Issued: 2019
- Authors: Ntemi, Pascal V , Walker, Roderick B , Khamanga, Sandile M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183503 , vital:44001 , xlink:href="https://doi.org/10.1691/ph.2019.8116"
- Description: Clarithromycin (CLA) is an extremely bitter macrolide antibiotic used to treat paediatric and adult infections. The bitter taste affects patient adherence and may compromise therapy. This research developed a taste masked CLA resinate using Indion® 234, a weak acidic cation exchange resin. The factors affecting formation of the CLA-resin complex were assessed. Design of experiments was used to optimize response while evaluating input variables such as temperature, CLA-resin ratio,stirring time and pH. CLA loading efficiency was determined spectrophotometrically and CLA release using USP Apparatus II. Differential Scanning Calorimetry (DSC), Scanning Electron Microscop (SEM), Fourier Transform Infrared (FT-IR) Spectroscopy and X-ray Diffraction (XRD) were used to confirm complex formation. A spectrophotometric method was used to assess taste evaluation. The optimum CLA-resin ratio, temperature, and stirring time were 1:4, 80 °C, 3 hours, respectively, at pH 8. Characterization techniques revealed that CLA was crystalline and the complex amorphous in nature. FT-IR spectra of resinate revealed the absence of resonance due to the tertiary amine functional group that is responsible for the bitter taste of CLA. CLA was stable in simulated salivary fluid and was released within 3 hours in gastric fluid. All CLAresin batches revealed complete taste masking. Taste analysis highlighted the improvement of taste masking properties of the resinate as the CLA to resin ratio, increased.
- Full Text:
- Date Issued: 2019
A comparative study of the effect of different stabilizers on the critical quality attributes of self-assembling nano co-crystals
- Witika, Bwalya A, Smith, Vincent J, Walker, Roderick B
- Authors: Witika, Bwalya A , Smith, Vincent J , Walker, Roderick B
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183224 , vital:43931 , xlink:href=" https://doi.org/10.3390/pharmaceutics12020182"
- Description: Lamivudine (3TC) and zidovudine (AZT) are antiviral agents used orally to manage HIV/AIDS infection. A pseudo one-solvent bottom-up approach was used to develop and produce nano co-crystals of 3TC and AZT. Equimolar amounts of 3TC dissolved in de-ionized water and AZT in methanol were rapidly injected into a pre-cooled vessel and sonicated at 4 °C. The resultant suspensions were characterized using a Zetasizer. The particle size, polydispersity index and Zeta potential were elucidated. Further characterization was undertaken using powder X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, and energy dispersive X-ray spectroscopy scanning electron microscopy. Different surfactants were assessed for their ability to stabilize the nano co-crystals and for their ability to produce nano co-crystals with specific and desirable critical quality attributes (CQA) including particle size (PS) less than 1000 nm, polydispersity index (PDI) less than 0.500 and Zeta potential (ZP) less than −30 mV. All surfactants produced co-crystals in the nanometer range. The PDI and PS are concentration-dependent for all nano co-crystals manufactured while only ZP was within specification when sodium dodecyl sulfate was used in the process.
- Full Text:
- Date Issued: 2020
- Authors: Witika, Bwalya A , Smith, Vincent J , Walker, Roderick B
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183224 , vital:43931 , xlink:href=" https://doi.org/10.3390/pharmaceutics12020182"
- Description: Lamivudine (3TC) and zidovudine (AZT) are antiviral agents used orally to manage HIV/AIDS infection. A pseudo one-solvent bottom-up approach was used to develop and produce nano co-crystals of 3TC and AZT. Equimolar amounts of 3TC dissolved in de-ionized water and AZT in methanol were rapidly injected into a pre-cooled vessel and sonicated at 4 °C. The resultant suspensions were characterized using a Zetasizer. The particle size, polydispersity index and Zeta potential were elucidated. Further characterization was undertaken using powder X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, and energy dispersive X-ray spectroscopy scanning electron microscopy. Different surfactants were assessed for their ability to stabilize the nano co-crystals and for their ability to produce nano co-crystals with specific and desirable critical quality attributes (CQA) including particle size (PS) less than 1000 nm, polydispersity index (PDI) less than 0.500 and Zeta potential (ZP) less than −30 mV. All surfactants produced co-crystals in the nanometer range. The PDI and PS are concentration-dependent for all nano co-crystals manufactured while only ZP was within specification when sodium dodecyl sulfate was used in the process.
- Full Text:
- Date Issued: 2020
Optimization of salbutamol sulfate dissolution from sustained release matrix formulations using an artificial neural network
- Chaibva, Faith A, Burton, Michael, Walker, Roderick B
- Authors: Chaibva, Faith A , Burton, Michael , Walker, Roderick B
- Date: 2010
- Subjects: Neural networks (Computer science)
- Language: English
- Type: Article
- Identifier: vital:6352 , http://hdl.handle.net/10962/d1006034
- Description: An artificial neural network was used to optimize the release of salbutamol sulfate from hydrophilic matrix formulations. Model formulations to be used for training, testing and validating the neural network were manufactured with the aid of a central composite design with varying the levels of Methocel® K100M, xanthan gum, Carbopol® 974P and Surelease® as the input factors. In vitro dissolution time profiles at six different sampling times were used as target data in training the neural network for formulation optimization. A multi layer perceptron with one hidden layer was constructed using Matlab®, and the number of nodes in the hidden layer was optimized by trial and error to develop a model with the best predictive ability. The results revealed that a neural network with nine nodes was optimal for developing and optimizing formulations. Simulations undertaken with the training data revealed that the constructed model was useable. The optimized neural network was used for optimization of formulation with desirable release characteristics and the results indicated that there was agreement between the predicted formulation and the manufactured formulation. This work illustrates the possible utility of artificial neural networks for the optimization of pharmaceutical formulations with desirable performance characteristics.
- Full Text:
- Date Issued: 2010
- Authors: Chaibva, Faith A , Burton, Michael , Walker, Roderick B
- Date: 2010
- Subjects: Neural networks (Computer science)
- Language: English
- Type: Article
- Identifier: vital:6352 , http://hdl.handle.net/10962/d1006034
- Description: An artificial neural network was used to optimize the release of salbutamol sulfate from hydrophilic matrix formulations. Model formulations to be used for training, testing and validating the neural network were manufactured with the aid of a central composite design with varying the levels of Methocel® K100M, xanthan gum, Carbopol® 974P and Surelease® as the input factors. In vitro dissolution time profiles at six different sampling times were used as target data in training the neural network for formulation optimization. A multi layer perceptron with one hidden layer was constructed using Matlab®, and the number of nodes in the hidden layer was optimized by trial and error to develop a model with the best predictive ability. The results revealed that a neural network with nine nodes was optimal for developing and optimizing formulations. Simulations undertaken with the training data revealed that the constructed model was useable. The optimized neural network was used for optimization of formulation with desirable release characteristics and the results indicated that there was agreement between the predicted formulation and the manufactured formulation. This work illustrates the possible utility of artificial neural networks for the optimization of pharmaceutical formulations with desirable performance characteristics.
- Full Text:
- Date Issued: 2010
Formulation and Characterisation of a Combination Captopril and Hydrochlorothiazide Microparticulate Dosage Form
- Chikukwa, Mellisa T R, Walker, Roderick B, Khamanga, Sandile M
- Authors: Chikukwa, Mellisa T R , Walker, Roderick B , Khamanga, Sandile M
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183200 , vital:43926 , xlink:href="https://doi.org/10.3390/pharmaceutics12080712"
- Description: Cardiovascular diseases such as hypertension and cardiac failure in South African children and adolescents are effectively managed long term, using a combination treatment of captopril and hydrochlorothiazide. The majority of commercially available pharmaceutical products are designed for adult patients and require extemporaneous manipulation, prior to administration to paediatric patients. There is a need to develop an age appropriate microparticulate dosing technology that is easy to swallow, dose and alter doses whilst overcoming the pharmacokinetic challenges of short half-life and biphasic pharmacokinetic disposition exhibited by hydrochlorothiazide and captopril. An emulsion solvent evaporation approach using different combinations of polymers was used to manufacture captopril and hydrochlorothiazide microparticles. Design of experiments was used to develop and analyse experimental data, and identifyoptimum formulation and process conditions for the preparation of the microparticles. Characterisation studies to establish encapsulation efficiency, in vitro release, shape, size and morphology of the microparticles were undertaken. The microparticles produced were in the micrometre size range, with an encapsulation efficiency >75% for both hydrochlorothiazide and captopril. The microparticulate technology is able to offer potential resolution to the half-life mediated dosing frequency of captopril as sustained release of the molecule was observed over a 12-h period. The release of hydrochlorothiazide of >80% suggests an improvement in solubility limited dissolution.
- Full Text:
- Date Issued: 2020
- Authors: Chikukwa, Mellisa T R , Walker, Roderick B , Khamanga, Sandile M
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183200 , vital:43926 , xlink:href="https://doi.org/10.3390/pharmaceutics12080712"
- Description: Cardiovascular diseases such as hypertension and cardiac failure in South African children and adolescents are effectively managed long term, using a combination treatment of captopril and hydrochlorothiazide. The majority of commercially available pharmaceutical products are designed for adult patients and require extemporaneous manipulation, prior to administration to paediatric patients. There is a need to develop an age appropriate microparticulate dosing technology that is easy to swallow, dose and alter doses whilst overcoming the pharmacokinetic challenges of short half-life and biphasic pharmacokinetic disposition exhibited by hydrochlorothiazide and captopril. An emulsion solvent evaporation approach using different combinations of polymers was used to manufacture captopril and hydrochlorothiazide microparticles. Design of experiments was used to develop and analyse experimental data, and identifyoptimum formulation and process conditions for the preparation of the microparticles. Characterisation studies to establish encapsulation efficiency, in vitro release, shape, size and morphology of the microparticles were undertaken. The microparticles produced were in the micrometre size range, with an encapsulation efficiency >75% for both hydrochlorothiazide and captopril. The microparticulate technology is able to offer potential resolution to the half-life mediated dosing frequency of captopril as sustained release of the molecule was observed over a 12-h period. The release of hydrochlorothiazide of >80% suggests an improvement in solubility limited dissolution.
- Full Text:
- Date Issued: 2020
A stability-indicating high performance liquid chromatographic (HPLC) assay for the simultaneous determination of atorvastatin and amlodipine in commercial tablets
- Mohammadi, Ali, Rezanour, N, Ansari Dogaheh, M, Ghorbani Bidkorbeh, F, Hashem, M, Walker, Roderick B
- Authors: Mohammadi, Ali , Rezanour, N , Ansari Dogaheh, M , Ghorbani Bidkorbeh, F , Hashem, M , Walker, Roderick B
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6403 , http://hdl.handle.net/10962/d1006340
- Description: A simple, rapid, precise and accurate isocratic reversed-phase stability-indicating HPLC method was developed and validated for the simultaneous determination of atorvastatin (AT) and amlodipine (AM) in commercial tablets. The method has shown adequate separation for AM, AT from their associated main impurities and their degradation products. Separation was achieved on a Perfectsil® Target ODS-3, 5 μm, 250 mm × 4.6 mm i.d. column using a mobile phase consisting of acetonitrile–0.025 M NaH2PO4 buffer (pH 4.5) (55:45, v/v) at a flow rate of 1 ml/min and UV detection at 237 nm. The drugs were subjected to oxidation, hydrolysis, photolysis and heat to apply stress conditions. The linearity of the proposed method was investigated in the range of 2–30 μg/ml (r = 0.9994) for AT and 1–20 μg/ml (r = 0.9993) for AM. The limits of detection were 0.65 μg/ml and 0.35 μg/ml for AT and AM, respectively. The limits of quantitation were 2 μg/ml and 1 μg/ml for AT and AM, respectively. Degradation products produced as a result of stress studies did not interfere with the detection of AT and AM and the assay can thus be considered stability-indicating.
- Full Text:
- Date Issued: 2007
- Authors: Mohammadi, Ali , Rezanour, N , Ansari Dogaheh, M , Ghorbani Bidkorbeh, F , Hashem, M , Walker, Roderick B
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6403 , http://hdl.handle.net/10962/d1006340
- Description: A simple, rapid, precise and accurate isocratic reversed-phase stability-indicating HPLC method was developed and validated for the simultaneous determination of atorvastatin (AT) and amlodipine (AM) in commercial tablets. The method has shown adequate separation for AM, AT from their associated main impurities and their degradation products. Separation was achieved on a Perfectsil® Target ODS-3, 5 μm, 250 mm × 4.6 mm i.d. column using a mobile phase consisting of acetonitrile–0.025 M NaH2PO4 buffer (pH 4.5) (55:45, v/v) at a flow rate of 1 ml/min and UV detection at 237 nm. The drugs were subjected to oxidation, hydrolysis, photolysis and heat to apply stress conditions. The linearity of the proposed method was investigated in the range of 2–30 μg/ml (r = 0.9994) for AT and 1–20 μg/ml (r = 0.9993) for AM. The limits of detection were 0.65 μg/ml and 0.35 μg/ml for AT and AM, respectively. The limits of quantitation were 2 μg/ml and 1 μg/ml for AT and AM, respectively. Degradation products produced as a result of stress studies did not interfere with the detection of AT and AM and the assay can thus be considered stability-indicating.
- Full Text:
- Date Issued: 2007
In vitro release of amoxycillin from lipophilic suppositories
- Webster, Jessica A, Dowse, Roslind, Walker, Roderick B
- Authors: Webster, Jessica A , Dowse, Roslind , Walker, Roderick B
- Date: 1998
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184377 , vital:44213 , xlink:href="https://doi.org/10.3109/03639049809085636"
- Description: The in vitro release characteristics of amoxycillin from different lipophilic suppository bases were investigated using the USP rotating basket method. Suppositories containing 250 mg amoxycillin were prepared in theobroma oil and in the semisynthetic bases Witepsol W35, Suppocire A32, Novata BD, and Novata 299. Both freshly prepared and 1-month-old suppositories were tested. Analysis of amoxycillin was performed using a validated high-performance liquid chromatographic (HPLC) technique. Release profiles differed significantly between bases, with the greatest amount of amoxycillin being released from both newly made and 1-month-old Novata BD bases (87.57 ± 8.18 and 99.66 ± 6.63%, respectively), and the lowest amount released from the newly manufactured theobroma suppositories (8.82 ± 0.75%) and the 1-month-old Suppocire A32 suppositories (7.78 ± 0.27%).
- Full Text:
- Date Issued: 1998
- Authors: Webster, Jessica A , Dowse, Roslind , Walker, Roderick B
- Date: 1998
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184377 , vital:44213 , xlink:href="https://doi.org/10.3109/03639049809085636"
- Description: The in vitro release characteristics of amoxycillin from different lipophilic suppository bases were investigated using the USP rotating basket method. Suppositories containing 250 mg amoxycillin were prepared in theobroma oil and in the semisynthetic bases Witepsol W35, Suppocire A32, Novata BD, and Novata 299. Both freshly prepared and 1-month-old suppositories were tested. Analysis of amoxycillin was performed using a validated high-performance liquid chromatographic (HPLC) technique. Release profiles differed significantly between bases, with the greatest amount of amoxycillin being released from both newly made and 1-month-old Novata BD bases (87.57 ± 8.18 and 99.66 ± 6.63%, respectively), and the lowest amount released from the newly manufactured theobroma suppositories (8.82 ± 0.75%) and the 1-month-old Suppocire A32 suppositories (7.78 ± 0.27%).
- Full Text:
- Date Issued: 1998
HPLC method for simultaneous analysis of ranitidine and metronidazole in dosage forms
- King'ori, Loti D, Walker, Roderick B
- Authors: King'ori, Loti D , Walker, Roderick B
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184790 , vital:44272 , xlink:href="https://doi.org/10.14233/ajchem.2014.15432"
- Description: A simple, rapid, precise and accurate stability indicating HPLC method for the simultaneous analysis of metronidazole and ranitidine in dosage forms has been developed and validated. Calibration curves for metronidazole and ranitidine exhibited linearity (R2 = 0.9995 for both compounds) over the concentration ranges investigated. The method was sensitive, selective and accurate for both compounds. Both drugs were found to be stable following acid hydrolysis studies. However, following alkali hydrolysis degradation of both compounds was observed. Furthermore metronidazole appeared to be stable following oxidative studies however ranitidine underwent complete degradation under these conditions. Both drugs were well resolved from the degradation products. The stability indicating chromatographic method has the necessary precision and accuracy for the simultaneous analysis of metronidazole and ranitidine in dosage forms.
- Full Text:
- Date Issued: 2014
- Authors: King'ori, Loti D , Walker, Roderick B
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184790 , vital:44272 , xlink:href="https://doi.org/10.14233/ajchem.2014.15432"
- Description: A simple, rapid, precise and accurate stability indicating HPLC method for the simultaneous analysis of metronidazole and ranitidine in dosage forms has been developed and validated. Calibration curves for metronidazole and ranitidine exhibited linearity (R2 = 0.9995 for both compounds) over the concentration ranges investigated. The method was sensitive, selective and accurate for both compounds. Both drugs were found to be stable following acid hydrolysis studies. However, following alkali hydrolysis degradation of both compounds was observed. Furthermore metronidazole appeared to be stable following oxidative studies however ranitidine underwent complete degradation under these conditions. Both drugs were well resolved from the degradation products. The stability indicating chromatographic method has the necessary precision and accuracy for the simultaneous analysis of metronidazole and ranitidine in dosage forms.
- Full Text:
- Date Issued: 2014
The comparison of in vitro release methods for the evaluation of oxytocin release from Pluronic® F127 parenteral formulations
- Chaibva, Faith A, Walker, Roderick B
- Authors: Chaibva, Faith A , Walker, Roderick B
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6351 , http://hdl.handle.net/10962/d1006033
- Description: The objective of these studies was to develop a discriminatory in vitro release test for assessing formulation factors that may affect oxytocin (OT) release during formulation development studies of a Pluronic® F127 OT in situ gel-forming parenteral dosage form. An appropriate release assessment method should be able to discriminate between the performance of different formulation compositions (1, 2), and this was the primary criterion used for selection of an appropriate test procedure during the test method development process. ANOVA and the difference (f1) and similarity (f2)factors were used to evaluate the discriminatory behavior of different test methods that were investigated in these studies. The in vitro release tests that were investigated included the use of USP Apparatus 1, 2, and 3; a dialysis bag in USP Apparatus 2; and a membrane-less diffusion method. It was concluded that the use of USP Apparatus 3 was best able to discriminate between OT release for the different formulations tested. USP Apparatus 3 was thus considered the most suitable in vitro release test apparatus for studying formulation factors affecting OT release during the development of a parenteral dosage form prepared using Pluronic® F127.
- Full Text:
- Date Issued: 2007
- Authors: Chaibva, Faith A , Walker, Roderick B
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6351 , http://hdl.handle.net/10962/d1006033
- Description: The objective of these studies was to develop a discriminatory in vitro release test for assessing formulation factors that may affect oxytocin (OT) release during formulation development studies of a Pluronic® F127 OT in situ gel-forming parenteral dosage form. An appropriate release assessment method should be able to discriminate between the performance of different formulation compositions (1, 2), and this was the primary criterion used for selection of an appropriate test procedure during the test method development process. ANOVA and the difference (f1) and similarity (f2)factors were used to evaluate the discriminatory behavior of different test methods that were investigated in these studies. The in vitro release tests that were investigated included the use of USP Apparatus 1, 2, and 3; a dialysis bag in USP Apparatus 2; and a membrane-less diffusion method. It was concluded that the use of USP Apparatus 3 was best able to discriminate between OT release for the different formulations tested. USP Apparatus 3 was thus considered the most suitable in vitro release test apparatus for studying formulation factors affecting OT release during the development of a parenteral dosage form prepared using Pluronic® F127.
- Full Text:
- Date Issued: 2007
The use of hot and cold high pressure homogenization to enhance the loading capacity and encapsulation efficiency of nanostructured lipid carriers for the hydrophilic antiretroviral drug, didanosine for potential administration to paediatric patients
- Kasongo, Kasongo W, Müller, Rainer H, Walker, Roderick B
- Authors: Kasongo, Kasongo W , Müller, Rainer H , Walker, Roderick B
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184087 , vital:44170 , xlink:href="https://doi.org/10.3109/10837450.2010.542163"
- Description: A major obstacle to the application of nanostructured lipid carriers (NLCs) as carriers for hydrophilic drugs is the limited loading capacity (LC) and encapsulation efficiency (EE) of NLCs for these molecules. The purpose of this research was to design and implement a strategy to enhance the LC and EE of NLCs for the hydrophilic drug, didanosine (DDI). DDI was dispersed in Transcutol® HP and the particle size of DDI in the liquid lipid was reduced gradually using hot high pressure homogenization (HPH). The product obtained thereafter was added to Precirol® ATO 5 and the hot mixture was immediately dried using liquid nitrogen. The dried materials were then ground and passed through a 200 μm sieve and the solid lipid particles were dispersed in a surfactant solution and subsequently used to manufacture DDI-loaded NLCs using cold HPH. The LC and EE of NLCs for DDI manufactured using the new strategy were 3.39 ± 0.63% and 51.58 ± 1.31%, respectively, compared to 0.079 ± 0.001% and 32.45 ± 0.08%, respectively, obtained when DDI-loaded NLCs were produced using conventional hot HPH. The enhanced LC and EE for DDI make NLCs a potential technology for the oral administration of DDI to paediatric patients.
- Full Text:
- Date Issued: 2012
- Authors: Kasongo, Kasongo W , Müller, Rainer H , Walker, Roderick B
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184087 , vital:44170 , xlink:href="https://doi.org/10.3109/10837450.2010.542163"
- Description: A major obstacle to the application of nanostructured lipid carriers (NLCs) as carriers for hydrophilic drugs is the limited loading capacity (LC) and encapsulation efficiency (EE) of NLCs for these molecules. The purpose of this research was to design and implement a strategy to enhance the LC and EE of NLCs for the hydrophilic drug, didanosine (DDI). DDI was dispersed in Transcutol® HP and the particle size of DDI in the liquid lipid was reduced gradually using hot high pressure homogenization (HPH). The product obtained thereafter was added to Precirol® ATO 5 and the hot mixture was immediately dried using liquid nitrogen. The dried materials were then ground and passed through a 200 μm sieve and the solid lipid particles were dispersed in a surfactant solution and subsequently used to manufacture DDI-loaded NLCs using cold HPH. The LC and EE of NLCs for DDI manufactured using the new strategy were 3.39 ± 0.63% and 51.58 ± 1.31%, respectively, compared to 0.079 ± 0.001% and 32.45 ± 0.08%, respectively, obtained when DDI-loaded NLCs were produced using conventional hot HPH. The enhanced LC and EE for DDI make NLCs a potential technology for the oral administration of DDI to paediatric patients.
- Full Text:
- Date Issued: 2012
Application of quality by design principles for optimizing process variables of Extrusion and Spheronization of a Captopril Pellet Formulation:
- Veerubhotla, Krishna, Walker, Roderick B
- Authors: Veerubhotla, Krishna , Walker, Roderick B
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/178312 , vital:40098 , DOI: 10.36468/pharmaceutical-sciences.624
- Description: Product development using quality by design is a proactive and risk-based approach that shifts the manufacturing process from empirical to science-based. Risk assessment was performed to identify and analyse risk areas for the manufacture of captopril pellets. Twelve experimental runs were performed using a Plackett-Burman screening design. Pareto plots revealed the effect of formulation and process variables on the responses monitored and facilitated the identification of the most critical parameters for optimization of the formulation. A response surface methodology approach in conjunction with a central composite design was used to optimize the Eudragit® RL 30D (15-30 ml), microcrystalline cellulose (20-40 % w/w), sodium starch glycolate (2-5 % w/w) and spheronizer speed (650-1050 rpm).
- Full Text:
- Date Issued: 2020
- Authors: Veerubhotla, Krishna , Walker, Roderick B
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/178312 , vital:40098 , DOI: 10.36468/pharmaceutical-sciences.624
- Description: Product development using quality by design is a proactive and risk-based approach that shifts the manufacturing process from empirical to science-based. Risk assessment was performed to identify and analyse risk areas for the manufacture of captopril pellets. Twelve experimental runs were performed using a Plackett-Burman screening design. Pareto plots revealed the effect of formulation and process variables on the responses monitored and facilitated the identification of the most critical parameters for optimization of the formulation. A response surface methodology approach in conjunction with a central composite design was used to optimize the Eudragit® RL 30D (15-30 ml), microcrystalline cellulose (20-40 % w/w), sodium starch glycolate (2-5 % w/w) and spheronizer speed (650-1050 rpm).
- Full Text:
- Date Issued: 2020
Synthesis and characterization of ZnO nanoparticle synthesized by a microwave-assisted combustion method and catalytic activity for the removal of ortho-nitrophenol
- Assi, Navid, Mohammadi, Ali, Sadr Manuchehri, Q, Walker, Roderick B
- Authors: Assi, Navid , Mohammadi, Ali , Sadr Manuchehri, Q , Walker, Roderick B
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183850 , vital:44075 , xlink:href="https://doi.org/10.1080/19443994.2014.891083"
- Description: ZnO nanoparticles were manufactured using microwave-assisted combustion. The structural and morphological properties of the nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy, and Fourier transform infrared spectroscopy. Photocatalytic degradation of ortho-nitrophenol (O-NP) in aqueous solution using the synthesized nanoparticles was performed under UV–C irradiation and is reported for the first time. The effect of the initial O-NP concentration, amount of photocatalyst, pH, and salt was investigated during photodegradation. Analysis of the degraded samples using HPLC with UV detection revealed that photocatalysis in the presence of ZnO nanoparticles removed 98% of the O-NP in 5 h. In addition, the photocatalytic degradation kinetics of O-NP were studied, and the results suggest that the data are best fitted to pseudo-first-order kinetic and Langmuir–Hinshelwood models.
- Full Text:
- Date Issued: 2015
- Authors: Assi, Navid , Mohammadi, Ali , Sadr Manuchehri, Q , Walker, Roderick B
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183850 , vital:44075 , xlink:href="https://doi.org/10.1080/19443994.2014.891083"
- Description: ZnO nanoparticles were manufactured using microwave-assisted combustion. The structural and morphological properties of the nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy, and Fourier transform infrared spectroscopy. Photocatalytic degradation of ortho-nitrophenol (O-NP) in aqueous solution using the synthesized nanoparticles was performed under UV–C irradiation and is reported for the first time. The effect of the initial O-NP concentration, amount of photocatalyst, pH, and salt was investigated during photodegradation. Analysis of the degraded samples using HPLC with UV detection revealed that photocatalysis in the presence of ZnO nanoparticles removed 98% of the O-NP in 5 h. In addition, the photocatalytic degradation kinetics of O-NP were studied, and the results suggest that the data are best fitted to pseudo-first-order kinetic and Langmuir–Hinshelwood models.
- Full Text:
- Date Issued: 2015
The use of experimental design for the development and validation of an HPLC-ECD method for the quantitation of efavirenz
- Makoni, Pedzisai A, Khamanga, Sandile M, Kasongo, Kasongo W, Walker, Roderick B
- Authors: Makoni, Pedzisai A , Khamanga, Sandile M , Kasongo, Kasongo W , Walker, Roderick B
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183556 , vital:44006 , xlink:href="https://doi.org/10.1691/ph.2018.8074"
- Description: A high performance liquid chromatography with electrochemical detection (HPLC-ECD) method for the quantitation of efavirenz (EFV) was developed, since traditional HPLC-UV methods may be inappropriate, given that EFV undergoes photolytic degradation following exposure to UV light. This work describes the use of response surface methodology (RSM) based on a central composite design (CCD) to develop a stability-indicating HPLC method with pulsed ECD in direct current (DC) mode at an applied potential difference and current of +1400 mV and 1.0 μA for the analysis of EFV. Separation of EFV and imipramine was achieved using a Nova-Pak®C18 cartridge column and a mobile phase of phosphate buffer (pH 4.5): acetonitrile (ACN) (55:45 v/v). Mobile phase pH, buffer molarity, ACN concentration and applied potential difference were investigated. The optimized method produced sharp well resolved peaks for imipramine and EFV with retention times of 3.70 and 8.89 minutes. The calibration curve was linear (R2 = 0.9979) over the range 5-70 μg/mL. Repeatability and intermediate precision ranged between 3.37 and 4.34 % RSD and 1.31 and 4.29 % RSD and accuracy between -0.80 and 4.71 % bias. The LOQ and LOD were 5.0 and 1.5 μg/mL. The method was specific for EFV and was used to analyse EFV in commercially available tablets. The HPLC-ECD method is more suitable for quantitative analysis of EFV than HPLC-UV.
- Full Text:
- Date Issued: 2018
- Authors: Makoni, Pedzisai A , Khamanga, Sandile M , Kasongo, Kasongo W , Walker, Roderick B
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183556 , vital:44006 , xlink:href="https://doi.org/10.1691/ph.2018.8074"
- Description: A high performance liquid chromatography with electrochemical detection (HPLC-ECD) method for the quantitation of efavirenz (EFV) was developed, since traditional HPLC-UV methods may be inappropriate, given that EFV undergoes photolytic degradation following exposure to UV light. This work describes the use of response surface methodology (RSM) based on a central composite design (CCD) to develop a stability-indicating HPLC method with pulsed ECD in direct current (DC) mode at an applied potential difference and current of +1400 mV and 1.0 μA for the analysis of EFV. Separation of EFV and imipramine was achieved using a Nova-Pak®C18 cartridge column and a mobile phase of phosphate buffer (pH 4.5): acetonitrile (ACN) (55:45 v/v). Mobile phase pH, buffer molarity, ACN concentration and applied potential difference were investigated. The optimized method produced sharp well resolved peaks for imipramine and EFV with retention times of 3.70 and 8.89 minutes. The calibration curve was linear (R2 = 0.9979) over the range 5-70 μg/mL. Repeatability and intermediate precision ranged between 3.37 and 4.34 % RSD and 1.31 and 4.29 % RSD and accuracy between -0.80 and 4.71 % bias. The LOQ and LOD were 5.0 and 1.5 μg/mL. The method was specific for EFV and was used to analyse EFV in commercially available tablets. The HPLC-ECD method is more suitable for quantitative analysis of EFV than HPLC-UV.
- Full Text:
- Date Issued: 2018
The use of response surface methodology in the evaluation of captopril microparticles manufactured using an oil in oil solvent evaporation technique
- Khamanga, Sandile M, Walker, Roderick B
- Authors: Khamanga, Sandile M , Walker, Roderick B
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184221 , vital:44191 , xlink:href="https://doi.org/10.3109/02652048.2011.629744"
- Description: Captopril (CPT) microparticles were manufactured by solvent evaporation using acetone (dispersion phase) and liquid paraffin (manufacturing phase) with Eudragit® and Methocel® as coat materials. Design of experiments and response surface methodology (RSM) approaches were used to optimize the process. The microparticles were characterized based on the percent of drug released and yield, microcapsule size, entrapment efficiency and Hausner ratio. Differential scanning calorimetry (DSC), Infrared (IR) spectroscopy, scanning electron microscopy (SEM) and in vitro dissolution studies were conducted. The microcapsules were spherical, free-flowing and IR and DSC thermograms revealed that CPT was stable. The percent drug released was investigated with respect to Eudragit® RS and Methocel® K100M, Methocel® K15M concentrations and homogenizing speed. The optimal conditions for microencapsulation were 1.12 g Eudragit® RS, 0.67 g Methocel® K100M and 0.39 g Methocel® K15M at a homogenizing speed of 1643 rpm and 89% CPT was released. The value of RSM-mediated microencapsulation of CPT was elucidated.
- Full Text:
- Date Issued: 2012
- Authors: Khamanga, Sandile M , Walker, Roderick B
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184221 , vital:44191 , xlink:href="https://doi.org/10.3109/02652048.2011.629744"
- Description: Captopril (CPT) microparticles were manufactured by solvent evaporation using acetone (dispersion phase) and liquid paraffin (manufacturing phase) with Eudragit® and Methocel® as coat materials. Design of experiments and response surface methodology (RSM) approaches were used to optimize the process. The microparticles were characterized based on the percent of drug released and yield, microcapsule size, entrapment efficiency and Hausner ratio. Differential scanning calorimetry (DSC), Infrared (IR) spectroscopy, scanning electron microscopy (SEM) and in vitro dissolution studies were conducted. The microcapsules were spherical, free-flowing and IR and DSC thermograms revealed that CPT was stable. The percent drug released was investigated with respect to Eudragit® RS and Methocel® K100M, Methocel® K15M concentrations and homogenizing speed. The optimal conditions for microencapsulation were 1.12 g Eudragit® RS, 0.67 g Methocel® K100M and 0.39 g Methocel® K15M at a homogenizing speed of 1643 rpm and 89% CPT was released. The value of RSM-mediated microencapsulation of CPT was elucidated.
- Full Text:
- Date Issued: 2012
Syntheses, protonation constants and antimicrobial activity of 2-substituted N-alkylimidazole derivatives
- Kleyi, Phumelele, Walmsley, Ryan S, Gundhla, Isaac Z, Walmsley, Tara A, Jauka, Tembisa I, Dames, Joanna F, Walker, Roderick B, Torto, Nelson, Tshentu, Zenixole R
- Authors: Kleyi, Phumelele , Walmsley, Ryan S , Gundhla, Isaac Z , Walmsley, Tara A , Jauka, Tembisa I , Dames, Joanna F , Walker, Roderick B , Torto, Nelson , Tshentu, Zenixole R
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184066 , vital:44165 , xlink:href="https://www.ajol.info/index.php/sajc/article/view/123858"
- Description: A series of N-alkylimidazole-2-carboxylic acid, N-alkylimidazole-2-carboxaldehyde and N-alkylimidazole-2-methanol derivatives [alkyl = benzyl, methyl, ethyl, propyl, butyl, heptyl, octyl and decyl] have been synthesized and the protonation constants determined. The antimicrobial properties of the compounds were tested against Gram-negative (Escherichi coli), Gram-positive (Staphylococcus aureus and Bacillus subtilis subsp. spizizenii) bacterial strains and yeast (C. albicans). Both the disk diffusion and broth microdilution methods for testing the antimicrobial activity showed that N-alkylation of imidazole with longer alkyl chains and the substitution with low pKa group at 2-position resulted in enhanced antimicrobial activity. Particularly, the N-alkylimidazole-2-carboxylic acids exhibited the best antimicrobial activity due to the low pKa of the carboxylic acid moiety. Generally, all the N-alkylimidazole derivatives were most active against the Gram-positive bacteria [S. aureus (MIC = 5–160 µg mL–1) and B. subtilis subsp. spizizenii (5–20 µg mL–1)], with the latter more susceptible. All the compounds showed poor antimicrobial activity against both Gram-negative (E. coli, MIC = 0.15 to >2500 µg mL–1) bacteria and all the compounds were inactive against the yeast (Candida albicans).
- Full Text:
- Date Issued: 2012
- Authors: Kleyi, Phumelele , Walmsley, Ryan S , Gundhla, Isaac Z , Walmsley, Tara A , Jauka, Tembisa I , Dames, Joanna F , Walker, Roderick B , Torto, Nelson , Tshentu, Zenixole R
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184066 , vital:44165 , xlink:href="https://www.ajol.info/index.php/sajc/article/view/123858"
- Description: A series of N-alkylimidazole-2-carboxylic acid, N-alkylimidazole-2-carboxaldehyde and N-alkylimidazole-2-methanol derivatives [alkyl = benzyl, methyl, ethyl, propyl, butyl, heptyl, octyl and decyl] have been synthesized and the protonation constants determined. The antimicrobial properties of the compounds were tested against Gram-negative (Escherichi coli), Gram-positive (Staphylococcus aureus and Bacillus subtilis subsp. spizizenii) bacterial strains and yeast (C. albicans). Both the disk diffusion and broth microdilution methods for testing the antimicrobial activity showed that N-alkylation of imidazole with longer alkyl chains and the substitution with low pKa group at 2-position resulted in enhanced antimicrobial activity. Particularly, the N-alkylimidazole-2-carboxylic acids exhibited the best antimicrobial activity due to the low pKa of the carboxylic acid moiety. Generally, all the N-alkylimidazole derivatives were most active against the Gram-positive bacteria [S. aureus (MIC = 5–160 µg mL–1) and B. subtilis subsp. spizizenii (5–20 µg mL–1)], with the latter more susceptible. All the compounds showed poor antimicrobial activity against both Gram-negative (E. coli, MIC = 0.15 to >2500 µg mL–1) bacteria and all the compounds were inactive against the yeast (Candida albicans).
- Full Text:
- Date Issued: 2012
Pharmacokinetics of cyclizine following intravenous administration to human volunteers
- Kanfer, Isadore, Walker, Roderick B
- Authors: Kanfer, Isadore , Walker, Roderick B
- Date: 1996
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184389 , vital:44214 , xlink:href="https://doi.org/10.1016/0928-0987(96)00177-7"
- Description: The pharmacokinetics of cyclizine, a piperazine derivative useful in the prevention and treatment of nausea and vomiting, was investigated in six healthy male volunteers following an intravenous bolus dose. The drug is extensively distributed with a mean volume of distribution of 16.50 ± 3.33 l/kg and a mean total clearance of 0.870 ± 0.105 l/h per kg. Urinary excretion data showed that less than one percent of the dose was excreted up to 36 h as unchanged drug in the urine. The extremely low mean renal clearance (0.005 ± 0.002 l/h per kg) for the parent drug comprised only a small proportion of total clearance indicating that urinary excretion of parent drug is not a major route of elimination for cyclizine. The drug appears to exhibit biexponential pharmacokinetics and has a terminal elimination half-life of approximately 13 h.
- Full Text:
- Date Issued: 1996
- Authors: Kanfer, Isadore , Walker, Roderick B
- Date: 1996
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184389 , vital:44214 , xlink:href="https://doi.org/10.1016/0928-0987(96)00177-7"
- Description: The pharmacokinetics of cyclizine, a piperazine derivative useful in the prevention and treatment of nausea and vomiting, was investigated in six healthy male volunteers following an intravenous bolus dose. The drug is extensively distributed with a mean volume of distribution of 16.50 ± 3.33 l/kg and a mean total clearance of 0.870 ± 0.105 l/h per kg. Urinary excretion data showed that less than one percent of the dose was excreted up to 36 h as unchanged drug in the urine. The extremely low mean renal clearance (0.005 ± 0.002 l/h per kg) for the parent drug comprised only a small proportion of total clearance indicating that urinary excretion of parent drug is not a major route of elimination for cyclizine. The drug appears to exhibit biexponential pharmacokinetics and has a terminal elimination half-life of approximately 13 h.
- Full Text:
- Date Issued: 1996
Analysis of macrolide antibiotics
- Kanfer, Isadore, Skinner, Michael F, Walker, Roderick B
- Authors: Kanfer, Isadore , Skinner, Michael F , Walker, Roderick B
- Date: 1998
- Language: English
- Type: Article , text
- Identifier: vital:7011 , http://hdl.handle.net/10962/d1008394 , http://www.sciencedirect.com/science/article/pii/S0021967398002763
- Description: The following macrolide antibiotics have been covered in this review: erythromycin and its related substances, azithromycin, clarithromycin, dirithromycin, roxithromycin, flurithromycin, josamycin, rokitamycin, kitasamycin, mycinamycin, mirosamycin, oleandomycin, rosaramicin, spiramycin and tylosin. The application of various thin-layer chromatography, paper chromatography, gas chromatography, high-performance liquid chromatography and capillary zone electrophoresis procedures for their analysis are described. These techniques have been applied to the separation and quantitative analysis of the macrolides in fermentation media, purity assessment of raw materials, assay of pharmaceutical dosage forms and the measurement of clinically useful macrolide antibiotics in biological samples such as blood, plasma, serum, urine and tissues. Data relating to the chromatographic behaviour of some macrolide antibiotics as well as the various detection methods used, such as bioautography, UV spectrophotometry, fluorometry, electrochemical detection, chemiluminescence and mass spectrometry techniques are also included.
- Full Text:
- Date Issued: 1998
- Authors: Kanfer, Isadore , Skinner, Michael F , Walker, Roderick B
- Date: 1998
- Language: English
- Type: Article , text
- Identifier: vital:7011 , http://hdl.handle.net/10962/d1008394 , http://www.sciencedirect.com/science/article/pii/S0021967398002763
- Description: The following macrolide antibiotics have been covered in this review: erythromycin and its related substances, azithromycin, clarithromycin, dirithromycin, roxithromycin, flurithromycin, josamycin, rokitamycin, kitasamycin, mycinamycin, mirosamycin, oleandomycin, rosaramicin, spiramycin and tylosin. The application of various thin-layer chromatography, paper chromatography, gas chromatography, high-performance liquid chromatography and capillary zone electrophoresis procedures for their analysis are described. These techniques have been applied to the separation and quantitative analysis of the macrolides in fermentation media, purity assessment of raw materials, assay of pharmaceutical dosage forms and the measurement of clinically useful macrolide antibiotics in biological samples such as blood, plasma, serum, urine and tissues. Data relating to the chromatographic behaviour of some macrolide antibiotics as well as the various detection methods used, such as bioautography, UV spectrophotometry, fluorometry, electrochemical detection, chemiluminescence and mass spectrometry techniques are also included.
- Full Text:
- Date Issued: 1998
Development and Validation of a Stability-indicating RP-HPLC Method Using Quality by Design for Estimating Captopril
- Veerubhotla, Krishna, Walker, Roderick B
- Authors: Veerubhotla, Krishna , Walker, Roderick B
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183525 , vital:44003 , xlink:href="10.4172/pharmaceutical-sciences.1000478"
- Description: The applicability of a quality by design framework for the development of a sensitive, simple and selective, stability-indicating reversed-phase high-performance liquid chromatography analytical method for the analysis of captopril was investigated. Design of experiments using a central composite design approach was used for method development. Twenty experimental runs were performed with acetonitrile content ranging between 28 and 36 % v/v, pH from 2.8 to 3.6 and temperature between 22° and 32°. The experimental data obtained was used to derive a quadratic model for the retention time of captopril. The optimized method produced sharp peaks with good resolution (>2) for captopril and the internal standard with retention times of 3.1 and 6.2 min, respectively. The experimental data revealed that acetonitrile content in the mobile phase and pH are significant factors that affect the retention time and resolution of captopril. Normal probability plots revealed that the residual and predicted data fall approximately on a straight line, indicating that the experimental error for these studies was evenly distributed suggesting that the model could be used to navigate the design space. This approach is useful to expedite method development and optimization activities in analytical laboratories.
- Full Text:
- Date Issued: 2019
- Authors: Veerubhotla, Krishna , Walker, Roderick B
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183525 , vital:44003 , xlink:href="10.4172/pharmaceutical-sciences.1000478"
- Description: The applicability of a quality by design framework for the development of a sensitive, simple and selective, stability-indicating reversed-phase high-performance liquid chromatography analytical method for the analysis of captopril was investigated. Design of experiments using a central composite design approach was used for method development. Twenty experimental runs were performed with acetonitrile content ranging between 28 and 36 % v/v, pH from 2.8 to 3.6 and temperature between 22° and 32°. The experimental data obtained was used to derive a quadratic model for the retention time of captopril. The optimized method produced sharp peaks with good resolution (>2) for captopril and the internal standard with retention times of 3.1 and 6.2 min, respectively. The experimental data revealed that acetonitrile content in the mobile phase and pH are significant factors that affect the retention time and resolution of captopril. Normal probability plots revealed that the residual and predicted data fall approximately on a straight line, indicating that the experimental error for these studies was evenly distributed suggesting that the model could be used to navigate the design space. This approach is useful to expedite method development and optimization activities in analytical laboratories.
- Full Text:
- Date Issued: 2019