Binding of centchroman with human serum as determined by charcoal adsorption method

Rapid equilibrium dialysis, ultrafiltration or ultracentrifugation? Evaluation of methods to quantify the unbound fraction of substances in plasma

In pharmacokinetics plasma protein binding (PPB) is a well-established parameter impacting drug disposition. The unbound fraction (f_u) is arguably regarded the effective concentration at the target site. Pharmacology and toxicology, increasingly use in vitro models. The translation of in vitro concentrations to in vivo doses can be supported by toxicokinetic modelling, e.g. physiologically based toxicokinetic models (PBTK). PPB of a test substance is an input parameter for PBTK. We compared three methods to quantify f_u: rapid equilibrium dialysis (RED), ultrafiltration (UF) and ultracentrifugation (UC) using twelve substances covering a wide range of Log P_ow (-0.1 to 6.8) and molecular weights (151 and 531 g/mol): Acetaminophen, Bisphenol A, Caffeine, Colchicine, Fenarimol, Flutamide, Genistein, Ketoconazole, α-Methyltestosterone, Tamoxifen, Trenbolone and Warfarin. After RED and UF separation, three polar substances (Log P_ow < 2) were largely unbound (f_u > 70%), while more lipophilic substances were largely bound (f_u < 33%). Compared to RED or UF, UC resulted in a generally higher f_u of lipophilic substances. f_u obtained after RED and UF were more consistent with published data. For half of the substances, UC resulted in f_u higher than the reference data. UF, RED and both UF and UC, resulted in lower f_u of Flutamide, Ketoconazole and Colchicine, respectively. For f_u quantifications, the separation method should be selected according to the test substance's properties. Based on our data, RED is suitable for a broader range of substances while UC and UF are suitable for polar substances.

Development of silymarin topical formulation: In vitro and ex vivo dermal kinetics of silymarin

Silymarin constituents are extensively investigated in the treatment of skin disorders. The main constituents of silymarin include taxifolin (TX), silychristin (ST), silydianin (SDN), silybin A (SA), silybin B (SB), isosilybin A (ISA) and isosilybin B (ISB). The objective of the present study was to determine in-vitro dermal kinetics of individual silymarin constituents in human skin models and to develop a silymarin topical formulation. In-vitro studies indicate human skin binding of silymarin was in the range of 2.09 to 12.3% and half-life of silymarin constituents was > 15.5 h in epidermal and dermal cells. Topical silymarin cream was prepared using sulfobutylether-β-cyclodextrins as solubilizer and propylene glycol as permeation enhancer. The cream was subjected to ex-vivo human skin permeation studies. In ex-vivo studies, cumulative amount of TX, ST, SDN, SA, SB, ISA and ISB permeated across human cadaver skin at 24 h was 921 ± 13.5, 1992 ± 67.6, 345 ± 39.2, 1089 ± 45.0, 1770 ± 100, 1469 ± 81.5 and 1285 ± 33.1 ng/cm², respectively. The amount TX, ST, SDN, SA, SB, ISA and ISB retained after 24 h was 60.7 ± 8.2, 376 ± 45.5, 72.3 ± 6.9, 66.4 ± 8.0, 208 ± 31.3, 154 ± 12.4 and 102 ± 6.3 ng/mg of human cadaver skin, respectively. The study results demonstrate silymarin topical formulation could deliver significant amount of silymarin constituents into skin. The developed silymarin formulation could be beneficial for treatment or management of a broad spectrum of dermatological disorders.

Scoping review to map evidence on mechanism of action, pharmacokinetics, effectiveness and side effects of centchroman as a contraceptive pill

OBJECTIVE

To systematically identify and map the available evidence on effectiveness, side effects, pharmacokinetics and mechanism of action of centchroman as a contraceptive pill.

INTRODUCTION

Centchroman was introduced in the Indian national family planning programme in 2016 as a once-a-week short-term contraceptive pill/oral contraceptive. At present there are no WHO recommendations on this method of contraception. We examined the available evidence through a scoping review.

METHODS

A search was conducted inclusive to the years 1970-2019 on electronic databases, grey literature sources and reference lists of included studies to identify studies. The five stages of Arksey and O'Malley's scoping review framework were applied in undertaking this scoping review.

RESULTS

The review identified 33 studies conducted between 1976 and 2017. Two studies reported mechanism of action of centchroman. Pharmacokinetics was reported by five studies among non-breastfeeding women and four studies among breastfeeding women. Eight studies reported on effectiveness ranging from 93% to 100%. Pregnancies due to user failure ranged from 2.6% to 10.2%. Although side effects were reported in 13 studies, the incidence varied greatly between the studies. Continuous bleeding and prolonged cycles >45 days were the most commonly reported side effects. All studies conducted had a small sample size and the duration of follow-up of women was 12 months or less. Fifty-five per cent of studies were by the developers of the pill (Central Drug Research Institute) and results of the phase IV clinical trial were unavailable.

CONCLUSIONS

The scoping review shows that studies with robust designs and conducted in international context are lacking. Insufficient evidence exists on centchroman use as a postcoital contraceptive pill. The broad uncertainty in range of side effects and effectiveness in the studies implies insufficient evidence to make global recommendations on centchroman that is currently licensed as a contraceptive in India.

Liquid chromatography-tandem mass spectrometry based method development and validation of S016-1271 (LR8P), a novel cationic antimicrobial peptide for its application to pharmacokinetic studies

S016-1271 (LR8P) is a broad spectrum novel cationic antimicrobial peptide. The objective of the present study was to develop a selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) based bioanalytical method of S016-1271 peptide in mice and human plasma in order to uncover its pharmacokinetic aspects. The chromatographic separation of S016-1271 (FR8P as internal standard) was achieved on a Waters™ X select CSH-C18 column (75 × 3.0 mm, 2.5 μ) using mixture of acetonitrile and triple distilled water (TDW) both containing 0.05% formic acid as mobile phase. A seven minute linear gradient method was designed to separate analytes from ion suppression at a flow rate of 0.3 mL/min. The extraction of analytes from mice and human plasma was performed through solid phase extraction technique using mixed mode weak cation exchange cartridge (Thermo SOLA WCX 10 mg 1CC) with an extraction recovery of analytes about 75%. Mass spectrometric detection of S016-1271 and FR8P was performed with optimized multiple reaction monitoring (MRM) transitions (Q1/Q3) at 658.8 [M+3H] ³⁺/653.2 [M+3H-NH₃] ³⁺ and 443.4 [M+5H]⁵⁺ /434.7 [y₁₂-NH₃]⁴⁺,respectively in positive electrospray ionization (ESI) mode. The linearity in mice and human plasma was established over a concentration range of 7.81-250 ng/mL with regression coefficient (r² > 0.99). The currently developed method was validated as per US-FDA guidelines and found to be within the acceptable limits. The method was successfully applied to intravenous (IV) pharmacokinetic study in mice wherein the levels were detected upto 24 h. The peptide demonstrated poor distribution characteristics which were demonstrated through volume of distribution at steady state (202.71 ± 47.02 mL/kg less than total body water of mice; 580 mL/kg). The clearance of the peptide predominantly occurred through central compartment (central clearance is 25 fold greater than peripheral clearance). Also, the in vitro pharmacokinetic studies demonstrated the stability of S016-1271 in plasma and high plasma protein binding in mice and humans.

Preclinical pharmacokinetics and ADME characterization of a novel anticancer chalcone, cardamonin

Cardamonin (CRD), a chalconoid obtained from several medicinal plants of Zingiberaceae family, had shown promising potential in cancer prevention and therapy. For further development and better pharmacological elucidation, we performed a series of in vitro and in vivo studies to characterize its preclinical pharmacokinetics. The study samples were analyzed using validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) and high performance liquid chromatography-ultra violet (HPLC-UV) methods. CRD is partially soluble (<10 μM) and possess high permeability (>0.2 × 10-4 cm/sec). It is moderately bound to plasma proteins (<50%). It shows partitioning in red blood cell (RBC) compartment with the partition coefficient between RBCs and plasma (K_RBC/P ) of 0.95 at 0 min to 1.39 at 60 min, indicating significant but slow RBC uptake. In mice, CRD is poorly absorbed after oral administration with 18% oral bioavailability. It possesses high clearance, short mean residence time, and high volume of distribution in mice. It exhibited multiple peak phenomena both after oral and intravenous administration and is excreted both as conjugated and unchanged CRD in bile. It is majorly excreted in faeces and negligibly in urine. The preclinical absorption, distribution, metabolism, and excretion data are expected to succour the future clinical investigations of CRD as a promising anticancer agent. Copyright © 2016 John Wiley & Sons, Ltd.

Rifabutin reduces systemic exposure of an antimalarial drug 97/78 upon co-administration in rats: An in-vivo &in-vitro analysis

OBJECTIVE

To determine the potential drug-drug interactions between anti-malarial candidate 97/78 and anti-tubercular drug rifabutin in-vivo in rats followed by in-vitro investigation of the underlying mechanisms of drug interaction.

METHODS

Single oral dose study was conducted in male and female rats at 40 mg/kg and 70 mg/kg for 97/78 and rifabutin respectively.

RESULTS

It was reported that rifabutin co-administration altered pharmacokinetics of 97/63 (active metabolite of 97/78). A significant decrease was reported in the systemic exposure of 97/63 by a factor of 3-4. The AUC0-last values were (4.03 ± 0.60) and (5.44 ± 1.15) μg h mL(-1) upon 97/78 administration alone, while the values were decreased to (1.13 ± 0.10) and (1.23 ± 1.13) μg h mL(-1) upon rifabutin co-administration in male and female rats respectively. Statistically significant differences were also reported in Cmax and Tmax values upon rifabutin co-administration. In-vitro drug metabolism study in rat liver microsomes has shown that the metabolism of 97/63 was increased by 10%-12% upon rifabutin co-incubation. The extent of plasma protein binding of 97/63 was found to be decreased from 54%-55% to 6%-8% upon rifabutin addition.

CONCLUSIONS

It was concluded that rifabutin co-administration altered PK parameters of 97/63 in SD rats. However, no intersex influences were reported in the interaction pattern. The results obtained in the in-vivo study were well correlated with the in-vitro findings and can further be applied to explore other aspects of potential drug interactions between these two drugs.

Effect of centchroman coadministration on the pharmacokinetics of metformin in rats

Objectives:

To study the effect of centchroman, a non-steroidal oral contraceptive, coadministration on the pharmacokinetics of metformin in rats.

Materials and Methods:

The pharmacokinetic interaction of metformin was studied in normal Sprague-Dawley female rats with and without centchroman coadministration. Blood samples were analyzed using a validated high-performance liquid chromatography method to generate the pharmacokinetic profile of metformin. The C_max and t_max were directly read from the concentration–time data. Other pharmacokinetic parameters were estimated using non-compartmental analyses.

Results:

Metformin was monitored up to 10 h, and it exhibited a double-peak phenomenon. The C_{max 1}, 2.62 ± 0.32 μg/ml, and C_{max 2,} 2.96 ± 0.65 μg/ml, occurred after 0.75 and 3 h post-dose, respectively. The mean residence time (MRT), AUC_{0-4 h} and volume of distribution (Vd/F) were 4.20 ± 0.30 h, 8.53 ± 1.89 μg.h/ml and 14.24 ± 5.42 L/kg, respectively. Following centchroman coadministration, metformin showed significantly (P < 0.05) higher C_max (C_{max 1,} 3.96 ± 0.55 μg/ml and C_{max 2,} 5.21 ± 0.59 μg/ml), AUC_{0-4 h} (12.28 ± 0.73 μg.h/ml) and Vd/F (18.29 ± 1.19 L/kg), but lower MRT (3.19 ± 0.36 h) than the values obtained after metformin dosing alone. However, AUC_0-t (17.74 ± 5.58 μg.h/ml) and clearance (3.76 ± 0.80 L/h/kg) remained unchanged.

Conclusions:

The results indicate that centchroman coadministration increases the rate but not the extent of absorption of metformin in rats. However, it does not seem to alter the pharmacokinetics of metformin to clinically significant levels.

Interspecies comparison of the pharmacokinetics and oral bioavailability of 99-357, a potent synthetic trioxane antimalarial compound

The pharmacokinetic data obtained in lower animals is of considerable importance in drug discovery and development. The objective of the present study was to generate in vitro and in vivo preclinical pharmacokinetic data of 99-357, a synthetic trioxane antimalarial, in rats and rabbits and to scale-up the data in order to apply for further studies. The pharmacokinetic profile of 99-357 was investigated after both intravenous and oral dose in rats and rabbits. Oral studies were carried out at three dose levels 6, 12 and 24mg/kg in rats while in rabbit only one dose level was selected. Both compartmental and non-compartmental approaches were used to calculate the pharmacokinetic parameters following intravenous and oral doses in both the species. The clearance in rat and rabbit was 45-57% and 60-67% respectively of hepatic blood flow. The plasma protein binding in rats was approximately 75%. In vitro studies showed high RBC partitioning and low to moderate hepatic clearance. Linearity was observed in terms of dose and AUCs suggesting linear pharmacokinetics at the dose levels studied in rats. The oral bioavailability of compound 99-357 in rat and rabbit at 12mg/kg dose level was comparable and 39% and 41% respectively.

Clinical pharmacokinetics and interaction of centchroman--a mini review

This article provides a brief review of the information available regarding the published pharmacokinetics data for the nonsteroidal, once-a-week oral contraceptive, centchroman (INN: ormeloxifene). This agent is a unique need-oriented contraceptive agent which is included in the National Family Welfare Programme of India. Since 1991, centchroman has been used as a need-oriented contraceptive and is being given for treating dysfunctional bleeding of the uterus. Information regarding absorption, tissue distribution, elimination and kinetic interactions is discussed.

In Vitro and In Vivo pharmacokinetic studies of bulaquine (analogue of primaquine), a novel antirelapse antimalarial, in rat, rabbit and monkey--highlighting species similarities and differences

Bulaquine (BQ) is a potent antirelapse antimalarial developed by CDRI, India. Bulaquine was rapidly absorbed in rats and rabbits with no distinct absorption phase while in monkeys a variable irregular absorption profile was observed. BQ was extensively converted to primaquine (PQ) after oral administration and the conversion was maximum in rats and minimum in rabbits, which is possibly due to the species difference. Clearance was higher in rats (3.2 l/h/kg) than in rabbits and monkeys (1.2 l/h/kg) and it was found be negligibly excreted in rat urine and feces. The elimination half-life in rats and rabbits was comparable after both oral and i.v. administration ( approximately 1.2 h). In all three species, PQ was resident in the body for a period longer than BQ. PQ, being the major active metabolite of BQ, might be responsible for the extended therapeutic effect of BQ. The oral bioavailability of BQ was 3.12%, 5.3% and 12% in rats, rabbits and monkeys, respectively, which could be mainly due to the high instability of BQ at acidic pH as demonstrated from a simulated gastric fluid stability study. Protein binding in various species was in the range 50-65% while the partition coefficient between RBCs and plasma (K(rbc/pl)) was between 0.75 and 1, indicating significant RBC uptake.

Determination of drug binding to plasma proteins using competitive equilibrium binding to dextran-coated charcoal

A method for determination of drug binding to plasma proteins, which is based on the comparison of drug affinities to plasma proteins and dextran-coated charcoal, is described. The method is free of nonspecific binding feature. The fractions unbound obtained by the charcoal method are in good agreement with values from a traditional ultrafiltration method for various low and highly bound compounds. The method presently requires drug concentrations much less than that of plasma proteins. A possibility of using the method to determine protein binding at an arbitrary drug concentration is discussed. A mechanism of nonspecific binding of drug to ultrafiltration membranes, which yields a good agreement with experimental observations, is suggested.

PET Imaging of the AT1 receptor with [11C]KR31173

AIM

The goal of this study was to investigate the binding characteristics of [(11)C]KR31173 and its applicability for PET studies of the AT(1) receptor (AT(1)R).

METHODS

Ex vivo biodistribution and pharmacology were tested in mice. PET imaging was performed in mice, beagle dogs and a baboon. To assess nonspecific binding, PET imaging was performed both before and after pretreatment with a potent AT(1)R antagonist. In the baboon, PET imaging was also performed with the previously developed radioligand [(11)C]L-159,884 for comparison.

RESULTS

Ex vivo biodistribution studies in mice showed specific binding rates of 80-90% in the adrenals, kidneys, lungs and heart. Specific binding was confirmed in mice using small animal PET. In dogs, renal cortex tissue concentration at 75-95 min postinjection (pi) was 63 nCi/ml per millicurie at a specific binding rate of 95%. In the baboon renal cortex, tissue activity at 55-75 min pi was 345 nCi/ml per millicurie. In the baboon the specific binding of [(11)C]KR31173 was higher (81%) than the specific binding of [(11)C]L-159,884 (34%).

CONCLUSION

[(11)C]KR31173 shows accumulation and significant specific binding to the AT(1)R in the kidneys of mice, dogs and baboon. These findings suggest that this radioligand is suited for imaging the renal cortical AT(1)R in multiple species.

Centchroman, a selective estrogen receptor modulator, as a contraceptive and for the management of hormone-related clinical disorders

DL-Centchroman (67/20; INN: Ormeloxifene) synthesized at the Central Drug Research Institute, Lucknow, is a nonsteroidal once-a-week oral contraceptive. It was introduced in Delhi in July, 1991, marketed in India in 1992 as Saheli and Choice-7 (Hindustan Latex Ltd., Thiruvananthapuram) and Centron (Torrent Pharmaceuticals India Ltd., Ahmedabad), and included in the National Family Welfare Programme in 1995.5 According to post-marketing surveillance, approximately 100,000 women were using this pill and approximately 1100,000 menstrual cycles were covered until 1996. It is a unique need-oriented contraceptive being effective when taken immediately after coitus or routinely as a weekly pill and has the advantage of less frequent administration. Its contraceptive action is quickly reversible. It has long terminal serum halflife of 168 hr in women and exhibits duration of anti-implantation/estrogen antagonistic action of 120 hr, despite a short (24.1 hr) serum halflife, in the rat. In lactating women, it is excreted in milk in quantities considered unlikely to cause any deleterious effect on suckling babies. In phase II and III multicentric trials as a contraceptive, children born of method-and-user failure pregnancies showed normal milestones, without any congenital anomaly. Reports of its promising action in the management of certain hormone-related clinical disorders are available. It has an excellent therapeutic index and is considered safe for chronic administration.