Protein binding of drugs is an important factor influencing both pharmacokinetic and pharmacodyna... more Protein binding of drugs is an important factor influencing both pharmacokinetic and pharmacodynamic parameters. Thus, knowing the extent of protein binding of drugs is crucial. Centchroman is a non-steroidal once a week oral contraceptive. It has been reported to be useful for the treatment of breast cancer and osteoporosis. Ample data has been generated on pharmacokinetics of centchroman in animals and humans. The extent of protein binding of centchroman has not been established so far. Non-specific adsorption of the drug limits the use of conventional methods like ultrafiltration and equilibrium dialysis. A method of charcoal adsorption as reported by Yuan et al. (method I) was used after modification (method II) to determine its binding to human serum. The extent of protein binding (%) is estimated from decline of percent drug remaining in the supernatant after adding the charcoal. Study was carried out at 1- and 10-microg/ml concentrations in drug free human serum samples and an HPLC assay was used to determine concentration-time data. The percentage of centchroman remaining in serum versus time data was analysed using non-linear fitting programs on WinNonlin software. Method II was found to give higher estimates of protein binding than the former method by preventing the dilution effect. Using this method, the extent of protein binding of centchroman was found to be 101.83+/-1.28 and 94.87+/-3.59% at 1 and 10 microg/ml, respectively. However, it was approximately 90% in the individual serum samples showing intersubject variability in protein binding of centchroman.
Centchroman (Ormeloxifene) is a nonsteroidal, selective estrogen receptor modulator, oral contrac... more Centchroman (Ormeloxifene) is a nonsteroidal, selective estrogen receptor modulator, oral contraceptive and anticancer agent, and is intended for long-term use by women. In view of its vast clinical application and the interaction of steroidal oral contraceptives with certain commonly used therapeutic agents, evaluation of interaction of certain concomitantly administered therapeutic agents (ibuprofen, rifampicin, diazepam, salbutamol, nifedipine, paracetamol, haloperidol, and tetracycline), in terms of both the postcoital contraceptive efficacy and pharmacokinetic profile, with centchroman was undertaken in female Sprague-Dawley rats. Among the representatives from each commonly used therapeutic category, interaction (pharmacokinetic) was observed with ibuprofen (60 mg/kg, twice daily), haloperidol (0.7 mg/kg, twice daily), and tetracycline (140 mg/kg, twice daily) coadministration on Days 1 through 5 postcoitum. Of these three therapeutic agents, only tetracycline interfered with the contraceptive efficacy of centchroman. It reduced the bioavailability of centchroman and its active metabolite by increasing their excretion through bile and feces. Increased metabolite excretion on tetracycline coadministration indicates the enterohepatic recirculation of the metabolite, not the parent drug. However, the effect of tetracycline was negated by the inclusion of lactic acid bacillus spores in the regimen.
The stereoselective disposition and metabolic inversion of ibuprofen were studied in 12 healthy s... more The stereoselective disposition and metabolic inversion of ibuprofen were studied in 12 healthy subjects under conditions of competitive and non-linear plasma protein binding. Each subject received each of four oral treatments according to a Latin-square design: 300 mg R(-)-ibuprofen, 300 mg S(+)-ibuprofen, 300 mg R(-)(-)+300 mg S(+)-ibuprofen, and 300 mg R(-)(-)+600 mg S(+)-ibuprofen. For a given treatment, the partial clearance of S(+)-ibuprofen was greater than that of R(-)-ibuprofen for all stereoisomeric drug species. Likewise, the unbound partial clearances of S(+)-ibuprofen were greater for most stereoisomeric drug species. There was also less difference among treatment groups when partial clearances were referenced to unbound as opposed to total plasma concentrations of enantiomer. The unbound intrinsic clearance and fractional inversion of R(-)-ibuprofen were unchanged across the four treatments, and chiral inversion was systemic, averaging 69%. In conclusion, stereoselective differences exist for the partial and composite clearances of R(-)- and S(+)-ibuprofen even when corrected for differences in plasma protein binding. However, differences among treatment groups for a particular elimination pathway are largely due to ibuprofen's non-linear binding.
Drug-resistant Plasmodium falciparum malaria necessitates development of novel drugs for treatmen... more Drug-resistant Plasmodium falciparum malaria necessitates development of novel drugs for treatment.The present study assessed the efficacy and safety of 3 dose levels of arterolane (RBx 11160), a synthetic trioxolane, for treatment of acute uncomplicated falciparum malaria. In this randomized, double-blind, multicenter, parallel-group, dose-finding, phase II trial, 230 patients from 4 centers in Thailand, India, and Tanzania (mainland and Zanzibar) received either 50 mg (n=78), 100mg (n=76), or 200 mg (n=76) of arterolane once daily for 7 days. Patients (aged 13-65 years) with asexual parasite density of 1000-100,000 parasites/microL were included and were followed up for 28 days. The median time to 90% parasite clearance (PC90) was evaluated. The median PC90 was longer in the group receiving the 50-mg dose (19.4 h), compared with the groups receiving the 100-mg dose (12.8 h) and 200-mg dose (12.6 h) (P < .01). The polymerase chain reaction-corrected adequate clinical and parasit...
1Metabolism and Pharmacokinetics Department, Ranbaxy Research Laboratories,Plot No. 20, Sector-18... more 1Metabolism and Pharmacokinetics Department, Ranbaxy Research Laboratories,Plot No. 20, Sector-18, Gurgaon, Haryana 122015, India 2Department of Medical Affairs and Clinical Research,Ranbaxy Research Laboratories, Plot no. 77B, Sector 18,Udyog Vihar ...
There are several clinically useful endoperoxides, mainly artemisinin derivatives available in ma... more There are several clinically useful endoperoxides, mainly artemisinin derivatives available in market for the treatment of malaria. These are highly potent drugs, with fastest parasite reduction ratio, broadest parasite stage specificity and effectiveness against all species of plasmodium in human. Endoperoxides are crystalline compounds having poor aqueous solubility. Several theories have been proposed for their mechanism of action, but the understanding is still incomplete. The major limitation of this class of compounds is the short half-life, requiring frequent administration, leading to noncompliance and recrudescence. Therefore, WHO recommends their use in combination with long acting antimalarial drugs (Artemisinin based combination therapy, ACT) to manage drug resistance, recrudescence, and non compliance. Endoperoxide compounds bind selectively to malaria-infected red blood cells and moderately to human plasma proteins. Artemisinin derivatives are converted primarily to the bioactive metabolite dihydroartemisinin after parenteral, oral or rectal administration. The rate of conversion is lowest for artelinic acid and highest for the water-soluble artesunate. Such conversion occurs largely in the liver by CYP enzymes. Oral bioavailability in animals ranges between 19 to 35%. Based on their liphophilicity, they tend to cross the blood-brain barrier, causing neurotoxicity in animal models. Efforts have been made to understand and develop pharmacokinetic-pharmacodynamic (PK-PD) correlation and identify PK-PD indices of endoperoxides. In the absence of the above, the selection of doses in ACTs has been empirical. There are several reports on clinical pharmacokinetic interactions of endoperoxides and their long acting partner drugs but as on date no clinically significant interaction has been reported. This review is an update on physicochemical, pharmacokinetic and pharmacodynamic properties of the endoperoxide antimalarials.
A rapid, specific and robust assay based on protein precipitation and liquid chromatography-elect... more A rapid, specific and robust assay based on protein precipitation and liquid chromatography-electrospray ionization tandem mass spectrometry (LC–ESI–MS–MS) has been developed and validated for the quantitative analysis of lumefantrine, an antimalarial drug, in human plasma using piperazine bis chloroquinoline as internal standard (ISTD). The precursor to product ion transitions of m/z 528.2 → 510.3 and m/z 409.2 → 205.1 were used to measure the analyte and the ISTD, respectively. Analysis was performed on C8 column (50 mm × 4.6 mm, 5 μm) with 10 mM ammonium acetate/acetonitrile/0.05% acetic acid (10/85/5, v/v) as mobile phase at a flow rate of 0.6 mL min−1. The assay exhibited a linear dynamic range of 0.21–25.05 μg mL−1. The RSD% of intra-day and inter-day assay was ≤15%. The application of this assay was demonstrated in a bioequivalence study and will be ideal for pharmacokinetic studies in pediatric population.
A rapid, specific and robust bioanalytical method for quantification of fenofibric acid, the acti... more A rapid, specific and robust bioanalytical method for quantification of fenofibric acid, the active form of fenofibrate, a hypolipidemic agent, was developed and validated in micro volumes (35 μL) of human plasma by liquid chromatography-electrospray ionization tandem mass spectrometry in negative ion mode. Fluvastatin was used as an internal standard. Precursor to product ion transitions of m/z 317.0 → 231.0 and m/z 410.2 → 348.1 were used to measure the analyte and the internal standard (ISTD), respectively. Chromatographic separation was carried out in reverse phase conditions using Chromolith SpeedRod RP-18e column (50 mm × 4.6 mm i.d.) with an isocratic mobile phase consisting of water/acetonitrile (20/80, v/v, pH 6.5) at a flow rate of 0.7 mL min−1. The extraction procedure yielded a recovery of 104.06 and 95.57% for fenofibric acid and the internal standard, respectively. The assay exhibited a linear dynamic range of 0.05–14.84 μg mL−1. The RSD% of intra- and inter-day assay was ≤15%. For its sensitivity, reliability and lower plasma volume requirement, the proposed method is suitable for pharmacokinetic studies.
Piperaquine phosphate is an orally active bisquinolone antimalarial drug that has been used for t... more Piperaquine phosphate is an orally active bisquinolone antimalarial drug that has been used for the past 3 decades. The authors report the safety, tolerability, and pharmacokinetics of piperaquine from a classical controlled phase I study. It was a double-blind, randomized, parallel-group, placebo-controlled, and single- and multiple-dose study. During the rising single-dose study, single ascending oral doses of 500, 750, 1000, 1250, and 1500 mg of piperaquine phosphate were administered, whereas in rising multiple-dose study, once-daily ascending oral doses of 500, 750, 1000, and 1500 mg were administered for 3 consecutive days. Pharmacokinetic analysis for both the rising single- and multiple-dose studies was done using the noncompartmental approach. The mean apparent terminal half-life ranged from 11 to 23 days. Increase in exposure was less than dose proportional and linear. Piperaquine concentrations were measurable up to 60 days postdose. Multiple peaks were observed in the plasma piperaquine concentration—time profiles and exhibited 3- to 7-fold accumulation following multiple dosing. Piperaquine was well tolerated following single and multiple doses.
Arterolane (RBx 11160) maleate is a novel, rapidly acting synthetic trioxolane antimalarial compo... more Arterolane (RBx 11160) maleate is a novel, rapidly acting synthetic trioxolane antimalarial compound being developed by Ranbaxy Research Laboratories (Haryana, India). It is presently under phase III in combination with piperaquine phosphate. The present work reports the relationship between pharmacokinetic (PK) parameter (AUC0–8h on day 0/day 6) and indices of pharmacodynamic (PD) response (50% parasite clearance [PC50], 90% parasite clearance [PC90], parasite clearance time [PCT], recrudescence) from a phase II, double-blind, multicenter, randomized, parallel-group, dose-ranging trial. Patients with acute uncomplicated P. falciparum malaria were randomized to 1 of 3 arterolane maleate (50, 100, and 200 mg) doses for 7 consecutive days. Plasma concentration data were available from 78, 76, and 75 patients receiving a 50-, 100-, and 200-mg dose, respectively. Based on PD modeling, its limitations and assumptions, minimum 150-mg dose arterolane maleate was recommended to optimize the probability of maximum therapeutic benefits for an adult. Doses higher than 100 mg are unlikely to reduce the probability of recrudescence. This study re-stresses the need of combining short and long-acting drugs to prevent resistance development and minimize recrudescence.
US FDA released guidelines for bioanalytical method validation in 2001 and it became the basis fo... more US FDA released guidelines for bioanalytical method validation in 2001 and it became the basis for guidelines such as ANVISA and EMA. Even though there is a general agreement between these guidelines in terms of evaluation of validation parameters, significant diversity exists with respect to methodology employed. Present review compares and summarizes the regulatory guidelines issued by US FDA, ANVISA and EMA for bioanalytical method validation. This review also discusses evaluation of certain validation parameters such as matrix effect, incurred sample reanalysis, various stability aspects, effect of anticoagulant counter ions, specificity in the presence of concomitant medications, and identification of pharmacokinetic repeats wherein specific guidance and general consensus amongst scientific community does not exist.
Protein binding of drugs is an important factor influencing both pharmacokinetic and pharmacodyna... more Protein binding of drugs is an important factor influencing both pharmacokinetic and pharmacodynamic parameters. Thus, knowing the extent of protein binding of drugs is crucial. Centchroman is a non-steroidal once a week oral contraceptive. It has been reported to be useful for the treatment of breast cancer and osteoporosis. Ample data has been generated on pharmacokinetics of centchroman in animals and humans. The extent of protein binding of centchroman has not been established so far. Non-specific adsorption of the drug limits the use of conventional methods like ultrafiltration and equilibrium dialysis. A method of charcoal adsorption as reported by Yuan et al. (method I) was used after modification (method II) to determine its binding to human serum. The extent of protein binding (%) is estimated from decline of percent drug remaining in the supernatant after adding the charcoal. Study was carried out at 1- and 10-microg/ml concentrations in drug free human serum samples and an HPLC assay was used to determine concentration-time data. The percentage of centchroman remaining in serum versus time data was analysed using non-linear fitting programs on WinNonlin software. Method II was found to give higher estimates of protein binding than the former method by preventing the dilution effect. Using this method, the extent of protein binding of centchroman was found to be 101.83+/-1.28 and 94.87+/-3.59% at 1 and 10 microg/ml, respectively. However, it was approximately 90% in the individual serum samples showing intersubject variability in protein binding of centchroman.
Centchroman (Ormeloxifene) is a nonsteroidal, selective estrogen receptor modulator, oral contrac... more Centchroman (Ormeloxifene) is a nonsteroidal, selective estrogen receptor modulator, oral contraceptive and anticancer agent, and is intended for long-term use by women. In view of its vast clinical application and the interaction of steroidal oral contraceptives with certain commonly used therapeutic agents, evaluation of interaction of certain concomitantly administered therapeutic agents (ibuprofen, rifampicin, diazepam, salbutamol, nifedipine, paracetamol, haloperidol, and tetracycline), in terms of both the postcoital contraceptive efficacy and pharmacokinetic profile, with centchroman was undertaken in female Sprague-Dawley rats. Among the representatives from each commonly used therapeutic category, interaction (pharmacokinetic) was observed with ibuprofen (60 mg/kg, twice daily), haloperidol (0.7 mg/kg, twice daily), and tetracycline (140 mg/kg, twice daily) coadministration on Days 1 through 5 postcoitum. Of these three therapeutic agents, only tetracycline interfered with the contraceptive efficacy of centchroman. It reduced the bioavailability of centchroman and its active metabolite by increasing their excretion through bile and feces. Increased metabolite excretion on tetracycline coadministration indicates the enterohepatic recirculation of the metabolite, not the parent drug. However, the effect of tetracycline was negated by the inclusion of lactic acid bacillus spores in the regimen.
The stereoselective disposition and metabolic inversion of ibuprofen were studied in 12 healthy s... more The stereoselective disposition and metabolic inversion of ibuprofen were studied in 12 healthy subjects under conditions of competitive and non-linear plasma protein binding. Each subject received each of four oral treatments according to a Latin-square design: 300 mg R(-)-ibuprofen, 300 mg S(+)-ibuprofen, 300 mg R(-)(-)+300 mg S(+)-ibuprofen, and 300 mg R(-)(-)+600 mg S(+)-ibuprofen. For a given treatment, the partial clearance of S(+)-ibuprofen was greater than that of R(-)-ibuprofen for all stereoisomeric drug species. Likewise, the unbound partial clearances of S(+)-ibuprofen were greater for most stereoisomeric drug species. There was also less difference among treatment groups when partial clearances were referenced to unbound as opposed to total plasma concentrations of enantiomer. The unbound intrinsic clearance and fractional inversion of R(-)-ibuprofen were unchanged across the four treatments, and chiral inversion was systemic, averaging 69%. In conclusion, stereoselective differences exist for the partial and composite clearances of R(-)- and S(+)-ibuprofen even when corrected for differences in plasma protein binding. However, differences among treatment groups for a particular elimination pathway are largely due to ibuprofen&amp;amp;#39;s non-linear binding.
Drug-resistant Plasmodium falciparum malaria necessitates development of novel drugs for treatmen... more Drug-resistant Plasmodium falciparum malaria necessitates development of novel drugs for treatment.The present study assessed the efficacy and safety of 3 dose levels of arterolane (RBx 11160), a synthetic trioxolane, for treatment of acute uncomplicated falciparum malaria. In this randomized, double-blind, multicenter, parallel-group, dose-finding, phase II trial, 230 patients from 4 centers in Thailand, India, and Tanzania (mainland and Zanzibar) received either 50 mg (n=78), 100mg (n=76), or 200 mg (n=76) of arterolane once daily for 7 days. Patients (aged 13-65 years) with asexual parasite density of 1000-100,000 parasites/microL were included and were followed up for 28 days. The median time to 90% parasite clearance (PC90) was evaluated. The median PC90 was longer in the group receiving the 50-mg dose (19.4 h), compared with the groups receiving the 100-mg dose (12.8 h) and 200-mg dose (12.6 h) (P < .01). The polymerase chain reaction-corrected adequate clinical and parasit...
1Metabolism and Pharmacokinetics Department, Ranbaxy Research Laboratories,Plot No. 20, Sector-18... more 1Metabolism and Pharmacokinetics Department, Ranbaxy Research Laboratories,Plot No. 20, Sector-18, Gurgaon, Haryana 122015, India 2Department of Medical Affairs and Clinical Research,Ranbaxy Research Laboratories, Plot no. 77B, Sector 18,Udyog Vihar ...
There are several clinically useful endoperoxides, mainly artemisinin derivatives available in ma... more There are several clinically useful endoperoxides, mainly artemisinin derivatives available in market for the treatment of malaria. These are highly potent drugs, with fastest parasite reduction ratio, broadest parasite stage specificity and effectiveness against all species of plasmodium in human. Endoperoxides are crystalline compounds having poor aqueous solubility. Several theories have been proposed for their mechanism of action, but the understanding is still incomplete. The major limitation of this class of compounds is the short half-life, requiring frequent administration, leading to noncompliance and recrudescence. Therefore, WHO recommends their use in combination with long acting antimalarial drugs (Artemisinin based combination therapy, ACT) to manage drug resistance, recrudescence, and non compliance. Endoperoxide compounds bind selectively to malaria-infected red blood cells and moderately to human plasma proteins. Artemisinin derivatives are converted primarily to the bioactive metabolite dihydroartemisinin after parenteral, oral or rectal administration. The rate of conversion is lowest for artelinic acid and highest for the water-soluble artesunate. Such conversion occurs largely in the liver by CYP enzymes. Oral bioavailability in animals ranges between 19 to 35%. Based on their liphophilicity, they tend to cross the blood-brain barrier, causing neurotoxicity in animal models. Efforts have been made to understand and develop pharmacokinetic-pharmacodynamic (PK-PD) correlation and identify PK-PD indices of endoperoxides. In the absence of the above, the selection of doses in ACTs has been empirical. There are several reports on clinical pharmacokinetic interactions of endoperoxides and their long acting partner drugs but as on date no clinically significant interaction has been reported. This review is an update on physicochemical, pharmacokinetic and pharmacodynamic properties of the endoperoxide antimalarials.
A rapid, specific and robust assay based on protein precipitation and liquid chromatography-elect... more A rapid, specific and robust assay based on protein precipitation and liquid chromatography-electrospray ionization tandem mass spectrometry (LC–ESI–MS–MS) has been developed and validated for the quantitative analysis of lumefantrine, an antimalarial drug, in human plasma using piperazine bis chloroquinoline as internal standard (ISTD). The precursor to product ion transitions of m/z 528.2 → 510.3 and m/z 409.2 → 205.1 were used to measure the analyte and the ISTD, respectively. Analysis was performed on C8 column (50 mm × 4.6 mm, 5 μm) with 10 mM ammonium acetate/acetonitrile/0.05% acetic acid (10/85/5, v/v) as mobile phase at a flow rate of 0.6 mL min−1. The assay exhibited a linear dynamic range of 0.21–25.05 μg mL−1. The RSD% of intra-day and inter-day assay was ≤15%. The application of this assay was demonstrated in a bioequivalence study and will be ideal for pharmacokinetic studies in pediatric population.
A rapid, specific and robust bioanalytical method for quantification of fenofibric acid, the acti... more A rapid, specific and robust bioanalytical method for quantification of fenofibric acid, the active form of fenofibrate, a hypolipidemic agent, was developed and validated in micro volumes (35 μL) of human plasma by liquid chromatography-electrospray ionization tandem mass spectrometry in negative ion mode. Fluvastatin was used as an internal standard. Precursor to product ion transitions of m/z 317.0 → 231.0 and m/z 410.2 → 348.1 were used to measure the analyte and the internal standard (ISTD), respectively. Chromatographic separation was carried out in reverse phase conditions using Chromolith SpeedRod RP-18e column (50 mm × 4.6 mm i.d.) with an isocratic mobile phase consisting of water/acetonitrile (20/80, v/v, pH 6.5) at a flow rate of 0.7 mL min−1. The extraction procedure yielded a recovery of 104.06 and 95.57% for fenofibric acid and the internal standard, respectively. The assay exhibited a linear dynamic range of 0.05–14.84 μg mL−1. The RSD% of intra- and inter-day assay was ≤15%. For its sensitivity, reliability and lower plasma volume requirement, the proposed method is suitable for pharmacokinetic studies.
Piperaquine phosphate is an orally active bisquinolone antimalarial drug that has been used for t... more Piperaquine phosphate is an orally active bisquinolone antimalarial drug that has been used for the past 3 decades. The authors report the safety, tolerability, and pharmacokinetics of piperaquine from a classical controlled phase I study. It was a double-blind, randomized, parallel-group, placebo-controlled, and single- and multiple-dose study. During the rising single-dose study, single ascending oral doses of 500, 750, 1000, 1250, and 1500 mg of piperaquine phosphate were administered, whereas in rising multiple-dose study, once-daily ascending oral doses of 500, 750, 1000, and 1500 mg were administered for 3 consecutive days. Pharmacokinetic analysis for both the rising single- and multiple-dose studies was done using the noncompartmental approach. The mean apparent terminal half-life ranged from 11 to 23 days. Increase in exposure was less than dose proportional and linear. Piperaquine concentrations were measurable up to 60 days postdose. Multiple peaks were observed in the plasma piperaquine concentration—time profiles and exhibited 3- to 7-fold accumulation following multiple dosing. Piperaquine was well tolerated following single and multiple doses.
Arterolane (RBx 11160) maleate is a novel, rapidly acting synthetic trioxolane antimalarial compo... more Arterolane (RBx 11160) maleate is a novel, rapidly acting synthetic trioxolane antimalarial compound being developed by Ranbaxy Research Laboratories (Haryana, India). It is presently under phase III in combination with piperaquine phosphate. The present work reports the relationship between pharmacokinetic (PK) parameter (AUC0–8h on day 0/day 6) and indices of pharmacodynamic (PD) response (50% parasite clearance [PC50], 90% parasite clearance [PC90], parasite clearance time [PCT], recrudescence) from a phase II, double-blind, multicenter, randomized, parallel-group, dose-ranging trial. Patients with acute uncomplicated P. falciparum malaria were randomized to 1 of 3 arterolane maleate (50, 100, and 200 mg) doses for 7 consecutive days. Plasma concentration data were available from 78, 76, and 75 patients receiving a 50-, 100-, and 200-mg dose, respectively. Based on PD modeling, its limitations and assumptions, minimum 150-mg dose arterolane maleate was recommended to optimize the probability of maximum therapeutic benefits for an adult. Doses higher than 100 mg are unlikely to reduce the probability of recrudescence. This study re-stresses the need of combining short and long-acting drugs to prevent resistance development and minimize recrudescence.
US FDA released guidelines for bioanalytical method validation in 2001 and it became the basis fo... more US FDA released guidelines for bioanalytical method validation in 2001 and it became the basis for guidelines such as ANVISA and EMA. Even though there is a general agreement between these guidelines in terms of evaluation of validation parameters, significant diversity exists with respect to methodology employed. Present review compares and summarizes the regulatory guidelines issued by US FDA, ANVISA and EMA for bioanalytical method validation. This review also discusses evaluation of certain validation parameters such as matrix effect, incurred sample reanalysis, various stability aspects, effect of anticoagulant counter ions, specificity in the presence of concomitant medications, and identification of pharmacokinetic repeats wherein specific guidance and general consensus amongst scientific community does not exist.
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