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Effect of concurrently coadministered drugs on the pharmacokinetic/pharmacodynamic profile of centchroman, a nonsteroidal oral contraceptive, in rats.

INTRODUCTION: Centchroman (international nonproprietary name: ormeloxifene) is a nonsteroidal selective estrogen receptor modulator, oral contraceptive, anticancer and antiosteoporotic agent that is intended for long-term use by women. In view of the vast clinical applications and interactions of steroidal oral contraceptives with commonly used therapeutic agents, the interaction potential of certain concomitantly administered therapeutic agents was investigated in terms of postcoital contraceptive efficacy (pharmacological) and the pharmacokinetic profile of centchroman in female Sprague-Dawley rats. The coadministered drugs used in the study were ciprofloxacin, cefixime, amoxicillin, metronidazole, amlodipine, atenolol, theophylline, metformin, pioglitazone and glibenclamide. MATERIALS AND METHODS: The pharmacological activity of centchroman was evaluated in sperm-positive female rats at 1.5 mg/kg, with or without coadministered drugs. Rats were sacrificed on Day 10 postcoitus, and autopsy was performed to check for the presence or absence of implantations. The estrogenic and antiestrogenic activities of centchroman were evaluated in immature ovariectomized rats. Pharmacokinetic interaction was studied in normal female rats with or without coadministered drugs. Serum samples were taken over 120 h and analyzed using a validated high-performance liquid chromatography method to generate the pharmacokinetic profile of centchroman. Pharmacokinetic parameters were estimated using noncompartmental analysis, and the results were compared. RESULTS: In pharmacological interaction studies, centchroman alone showed a 100% success rate when given alone or in the presence of coadministered drugs. The only exception was amoxicillin coadministration, with 66% rats in the group showing resorbed implantations. Further investigation with amoxicillin in ovariectomized immature rats indicates no alteration in the estrogenic and antiestrogenic profiles of centchroman. In pharmacokinetic interaction studies, most of the therapeutic agents affected the rate and extent of absorption of centchroman. In other pharmacokinetic parameters, clearance (CL) remained unchanged; however, there was decrease in bioavailability (F) and volume of distribution (V(d)) in some situations. CONCLUSIONS: The results indicate that there is no direct link between the altered pharmacokinetics of centchroman and the failure of pharmacological effect. The pharmacological interaction with amoxicillin could not be explained on the basis of alteration in the estrogenic and antiestrogenic activities of centchroman, indicating that different mechanisms are involved. The findings, however, suggest that amoxicillin coadministration may result in pharmacological interaction with centchroman and that caution should be taken in clinical practice.

Amoxicillin↗

Duration of anti-implantation action of the triphenylethylene anti-oestrogen centchroman in adult female rats.

The duration of the anti-implantation action of a single oral post-coital dose (1.25 mg kg-1) of a triphenylethylene anti-oestrogen, centchroman, was determined in adult rats. The effects of centchroman were compared with those of tamoxifen. In rats undergoing delay, centchroman administered orally on day 7 post-coitum prevented the induction of implantation of delayed blastocysts by an implantation inducing dose (1 micrograms per rat, s.c.) of oestrone which was administered earlier than 120 h after centchroman treatment. In tamoxifen (0.2 mg kg-1, orally) pretreated rats, oestrone administered at 144 h or later induced implantation. In cyclic rats treated with centchroman at intervals of 168 h and mated with males of proven fertility, implantation was prevented only when the interval between centchroman treatment and nidatory oestrogen secretion was less than 120 h. None of the females conceived when treated regularly at intervals of 120 h during exposure to fertile males. Discontinuation of treatment resulted in the occurrence of normal implantations in rats that mated 48 h or later after the last dose of centchroman, since in these animals the interval between anti-oestrogen treatment and nidatory oestrogen secretion was greater than 120 h. These findings suggest that the duration of the anti-implantation action of a single oral antifertility dose of centchroman in rats is about 120 h. Recovery of normal blastocysts from rats treated continuously with this dose of centchroman at these intervals suggests lack of significant effect on follicular maturation, ovulation, fertilization, preimplantation development or mating behaviour.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

Centchroman: a new non-steroidal oral contraceptive in human milk.

Centchroman, a non-steroidal oral contraceptive drug, was given to 13 nursing mothers comprising two groups. Each participant in group I (n = 8) received a single 30 mg dose, and in group II (n = 5) each participant received a 30 mg twice a week dose for twelve weeks. Simultaneous blood and milk samples were collected and analyzed for the parent drug by high performance liquid chromatography. In the single dose study (group I), the mean +/- peak centchroman concentrations in milk and serum were 78.7 +/- 28.4 and 63.6 +/- 23.6 ng/ml with milk-to-serum (M/S) ratio of 1.4 +/- 0.9. There was no significant increase in centchroman concentrations in milk after multiple dosing (group II). However, serum concentrations reached up to 112.5 ng/ml at 6 h after the 13th dose. Average M/S ratios were insignificantly different at trough (prior to next dose) and at peak (4-6 h after dose) centchroman levels. Additionally, the breast milk and serum centchroman concentrations showed a significant correlation (r = 0.64, P < 0.01), indicating that the amount of centchroman excreted into breast milk is dependent on serum concentrations. The weekly dose (% of the maternal dose) of centchroman ingested by the breast-fed infant at peak maternal serum and milk levels was in the range of 0.4 to 11.5%, assuming a weekly milk uptake of 1.05 l/kg. There was no significant difference in the dose ingested by the infants between the two dosing groups. These levels of centchroman passing into breast milk and subsequent exposure to the infants are unlikely to be of any physiological consequence.

Administration, Oral↗

Pharmacokinetic interaction of tetracycline with centchroman in healthy female volunteers.

OBJECTIVES: We aimed to investigate the effect of tetracycline coadministration, with and without lactic acid bacillus spores supplementation, on the pharmacokinetics of centchroman, a nonsteroidal oral contraceptive, in healthy female volunteers. PARTICIPANTS AND METHODS: The study was a single-centre, single-blinded, randomised, parallel treatment study in healthy female subjects of reproductive age randomised to two groups (11 subjects in each group). On day 1, subjects were given either a single oral dose of centchroman 30 mg with tetracycline 250 mg (group A) or a single dose of centchroman 30 mg, tetracycline 250 mg and one tablet containing 60 million lactic acid bacillus spores (group B). Tetracycline (250 mg three times daily) and lactic acid bacillus spores (one tablet three times daily) were continued for 3 days. Serial blood samples were collected and analysed by high performance liquid chromatography. The pharmacokinetic parameters were compared with the control data reported previously from this laboratory. RESULTS: Coadministration of tetracycline yielded significantly higher maximum plasma concentrations (C(max)) [35%] and a shorter time to reach C(max) (t(max)) values for centchroman (42%) than those obtained in the control group of females (p < 0.05). Inclusion of lactic acid bacillus spores in the regimen resulted in similar effects with increased C(max) (47%) and area under the concentration-time curve from time zero to infinity (34%) of centchroman (p < 0.05) with a significant decrease in t(max). Other parameters such as half-life, apparent clearance, apparent volume of distribution and mean residence time of centchroman were not affected by either of the treatments. CONCLUSIONS: The apparent effects of either of the regimens on centchroman pharmacokinetics seem to be of little clinical relevance in terms of increased rate or extent of availability. It can be concluded that this tetracycline-containing regimen is unlikely to alter the contraceptive efficacy of centchroman in humans.

Administration, Oral↗

Tissue distribution and pharmacokinetics of centchroman. A new nonsteroidal postcoital contraceptive agent and its 7-desmethyl metabolite in female rats after a single oral dose.

This study reports assay methodology, tissue distribution, and the basic pharmacokinetic behavior of centchroman and its 7-desmethyl metabolite [7-desmethyl centchroman (DMC)] after a single 12.5 mg/kg po dose in young female rats. Plasma, liver, lung, spleen, uterus, and adipose tissue were collected at various time intervals up to 14 days after dose. Reversed-phase HPLC, coupled with fluorescence detector, was used for simultaneous determination of centchroman and DMC in biosamples. The drug and metabolite were quantitated up to 2 and 5 ng/ml in plasma and 10 and 20 ng/g in tissues, respectively. The assay method was validated in terms of accuracy, precision, interassay, and intraassay variability, and was found to be reliable and reproducible. Peak centchroman levels in all of the tissues were found between 8-12 hr, whereas DMC peaks appeared between 8 and 24 hr, except that in liver the first peak of 1.2 micrograms/g appeared in the 1-hr sample. Tissue-to-plasma concentration ratios of centchroman were > 200 times in the lung; > 100 times in the spleen, liver, and adipose tissue; and > 40 times in the uterus at maxima in each tissue. Similarly, tissue concentrations of DMC were > 350 times in the lung, > 100 times in the liver and spleen, and > 25 times in the uterus and adipose tissue than in the plasma. High tissue-to-plasma concentration ratios of metabolites than the parent drug are indicative of its greater affinity for tissues. Terminal half-life of the centchroman and DMC in plasma were 24.1 and 36.6 hr, respectively. The mean residence time of centchroman was highest in the liver (78.4 hr), followed by the uterus (72.7 hr), adipose tissue (47.5 hr), lung (46 hr), spleen (44.1 hr), and plasma (37.7 hr). The mean residence time of DMC was also highest in the liver (133.7 hr), followed by the uterus (122 hr), adipose tissue (85.2 hr), lung (62.6 hr), spleen (62.6 hr), and plasma (48.2 hr).

Administration, Oral↗

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

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.

Adsorption↗

An X-ray crystallographic study of the nonsteroidal contraceptive agent centchroman.

We have determined an X-ray crystal structure for the N-methyl iodide derivative of the nonsteroidal contraceptive centchroman. The pendant aromatic substituents on C-3 and C-4 of the chroman system are nearly perpendicular to the plane of the chroman system, an orientation expected in such a chroman, but perturbed to some degree by the gem dimethyl substituents at C-2. Structural superposition with other nonsteroidal antiestrogens, tamoxifen and nafoxidine, shows a similar disposition of the tertiary amine side chains responsible for antagonist activity. The aryl rings also show good superposition, but in contrast to tamoxifen and nafoxidine, which have the potential for ring double bond conjugation, the centchroman aryl rings show a larger dihedral twist. While different superpositions between the enantiomers of centchroman and the bioactive enantiomer of estradiol (d-estradiol, 8 beta,9 alpha,13 beta,14 alpha,17 beta) are possible, when the chroman ring system is positioned over the AB rings of estradiol, then (3R,4R)-centchroman makes the best fit. The aryl substituents in both enantiomers make comparable overlays with the steroidal skeleton, but the axial methyl group at C-2 in (3R,4R)-centchroman is directed downward along the C-7 alpha axis of estradiol, a site where many substituents are known to be well tolerated by the estrogen receptor, while in the 3S,4S-enantiomer, this methyl group is projected upward. Thus, we suggest that the bioactive l-enantiomer of centchroman will have the 3R,4R absolute configuration.

Centchroman↗

The bone-specific estrogen centchroman inhibits osteoclastic bone resorption in vitro.

There is considerable interest in identifying bone-specific estrogen-like compounds with beneficial activities on bone and the cardiovascular system, but lacking side effects on the reproductive system. Two such compounds are currently under clinical investigation -raloxifene (Lilly) and centchroman (Novo-Nordisk). There is evidence suggesting that 17 beta-estradiol can inhibit osteoclastic bone resorption although this is somewhat controversial. Therefore, we examined the effect of centchroman and raloxifene, as well as 17 beta-estradiol, in the in vitro bone slice assay, where the direct effect of compounds on osteoclast activity can be assessed. Centchroman (0.001 - 1 microM) dose-dependently inhibited osteoclastic bone resorption up to 70% at 1 microM (p = 0.007) with an IC50 = 0.1 microM, while in contrast, raloxifene had no significant effect on bone resorption over the same dose range. 17 beta-estradiol (0.0001 - 1 microM) had a modest but significant inhibitory effect on resorption (40%, p < 0.05) at 1 microM, but no effect at lower physiological/therapeutic concentrations. Centchroman (1 microM) inhibited osteoclast cytoplasmic spreading by 32%, while raloxifene and 17 beta-estradiol were without effect. These results show that centchroman at therapeutic concentrations (ED50 approximately 1 mg/kg in animal models) is a potent inhibitor of osteoclastic bone resorption in vitro, suggesting that bone-specific estrogen-like molecules may have different mechanisms of action.

Animals↗

Glutaraldehyde and glyoxal cross-linked chitosan microspheres for controlled delivery of centchroman.

Glutaraldehyde and glyoxal cross-linked microspheres were prepared using chitosan with different molecular weights (MWs) and degrees of deacetylation (DDAs) for sustained release of centchroman under physiological conditions. The DDA in chitosan was determined by different methods, and the samples were categorized as chitosan with low (48%), medium (62%), and high (75%) DDA. The size and shape of the microspheres were determined by scanning electron microscopy (SEM), and hydrophobicity was determined by adsorption of Rose Bengal dye on microspheres cross-linked with glutaraldehyde or glyoxal. The effect of MW, DDA, and degree of cross-linking in microspheres was studied on the degree of swelling, as well as by the loading and release of centchroman. The glyoxal cross-linked microspheres were more compact and hydrophobic and showed better sustained release in companion to chitosan microspheres and glutaraldehyde cross-linked microspheres. The linear fractional release of centchroman with the square root of time indicated a Fickian behavior of centchroman, and the microspheres also showed zero-order release kinetics for centchroman.

Acetylation↗

Anticlastogenic effects of d- and l-centchroman in Swiss albino mice. 2. Subacute study in vivo and comparison with tamoxifen.

The antimutagenic effects of the two enantiomers of centchroman, a nonsteroidal oral contraceptive, were evaluated and compared with tamoxifen, a known breast cancer drug. Anticlastogenic assays in subacute in vivo studies in Swiss albino mice were used. They revealed that both d-centchroman and I-centchroman reduced the chromosome aberrations produced by dimethylbenz(a)anthracene and cyclophosphamide, when compared with the group treated only with the former mutagen. Tamoxifen also reduced the chromosome aberrations produced by the two mutagens. Overall the results showed that l-centchroman alone was more effective in reducing cyclophosphamide-induced aberrations than d-centchroman, and for toxicity reasons may be an alternative to tamoxifen in breast cancer therapy.

9,10-Dimethyl-1,2-benzanthracene↗

Ultrastructural effects of the nonsteroidal contraceptive centchroman on rat uterine luminal epithelium in early pregnancy.

Centchroman (3,4-trans-2,2-dimethyl-3-phenyl-4-p-(beta-pyrrolidinoethoxy) -phenyl-7-methoxychroman), a nonsteroidal contraceptive developed by the Central Drug Research Institute, Lucknow, India, was administered orally (1.25 mg/kg) to rats in a state of experimentally delayed implantation both during the progesterone treatment (preattachment stage) and in conjunction with the addition of estradiol (attachment stage). When given during preattachment, centchroman did not change the characteristic ultrastructure of the uterine epithelium significantly, except that there was an increase in the size and number of secondary lysosomes. Thus, no definite estrogenic or antiprogestational potency of centchroman was observed in this test system. However, when administered simultaneously with, before, or after estrogen during attachment, centchroman both abolished the estradiol-induced attachment reaction and produced or potentiated some changes of an estrogen type. Thus, no typical antiestrogen action but the sign of an estrogen action was observed in this test system. Further, the drug also produced certain specific changes in the lysosomal system of the epithelial cells during attachment. It is suggested that, in addition to some estrogenic effects, centchroman also possesses specific cellular effects, probably of a nonhormonal nature.

Animals↗

Anti-inflammatory and some other pharmacological effects of 3,4-trans-2,2-dimethyl-3-phenyl-4-(p-(beta-pyrrolidinoethoxy)-phenyl)-7-methoxy-chroman (Centchroman).

1. Anti-inflammatory, analgesic, antipyretic and other pharmacological activities of a new chroman derivative, Centchroman, have been described.2. Centchroman was found to possess significant anti-inflammatory action in the carrageenin-induced oedema test in mice and rats. It inhibited granuloma formation in the cotton pellet test. The anti-arthritic activity was also evident in formaldehyde-induced arthritis and adjuvant-induced arthritis in rats.3. Centchroman had a lower ulcerogenic index than phenylbutazone.4. The mechanism of the anti-inflammatory action of Centchroman seemed to be independent of endogenous adrenocortical hormones or of its weak oestrogenic activity.5. Centchroman antagonized phenylquinone writhing and bradykinin-induced bronchospasm but was devoid of any antipyretic activity.

Adrenal Glands↗

Prostanoid mediated effects of centchroman, a non-steroidal oral contraceptive.

The effect of centchroman, a non-steroidal oral contraceptive, has been studied on platelet aggregation and on the products of arachidonate metabolism. Centchroman inhibited platelet aggregation in vitro and ex vivo after acute as well as chronic treatment for one year in laboratory animals. It did not affect aggregation of platelets in women taking centchroman for one year. It is an inhibitor of platelet cyclooxygenase as indicated by the inhibition of malonaldehyde and thromboxane B2 but has no effect on vascular cyclooxygenase activity ex vivo or at low concentration in vitro. Thus, centchroman is a safe antifertility agent without risk of thrombotic episodes associated with hormonal oral contraceptives.

Adenosine Diphosphate↗

Effect of long-term centchroman treatment on plasma steroid and peptide hormones in female rhesus monkeys (Macaca mulatta).

Effect of weekly oral administration of Centchroman (3,4-trans-2, 2-dimethyl-3-phenyl-4-(p-(beta-pyrrolidinoethoxy)-phenyl)-7-met hoxychroman) at 1 and 2.5 mg/kg for 12 months on plasma estradiol, progesterone, luteinizing hormone and follicle stimulating hormone of female rhesus monkeys was studied. Centchroman administration at both doses did not disturb the menstrual pattern of rhesus monkeys except for a prolongation of the first treatment cycle. The subsequent cycles were of normal duration. The general pattern of plasma estradiol, progesterone, luteinizing hormone and follicle stimulating hormone was not affected by Centchroman treatment. The basal and peak levels were similar in pretreatment, control and treatment cycles. The results clearly indicate that Centchroman treatment up to 1 year does not affect the hypothalamo-pituitary-ovarian axis in female rhesus monkeys.

Administration, Oral↗

Evaluation of interaction potential of certain concurrently administered drugs with pharmacological and pharmacokinetic profile of centchroman in rats.

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.

Animals↗

High performance liquid chromatographic (HPLC) determination of centchroman in human serum and application to single-dose pharmacokinetics.

A simple and sensitive (2 ng/ml) HPLC method with fluorescence detection has been developed to measure serum concentrations of centchroman, a new nonsteroidal antifertility agent. The method was sufficiently sensitive to follow the drug over 21 days in human volunteers. Pharmacokinetic parameters of centchroman were determined after a single oral dose of 60 mg (2 x 30-mg tablets) in two healthy female volunteers. Centchroman is slowly eliminated from serum, showing a biexponential disappearance curve from serum. The terminal half-life of centchroman in the two volunteers was 168 and 175 hr, respectively.

Adult↗

Characterization of centchroman binding protein in plasma of rhesus monkey (Macaca mulatta).

Centchroman, a nonsteroidal antifertility agent was studied for its binding to monkey (Macaca mulatta) plasma proteins using charcoal adsorption and electrophoretic techniques. 14C-centchroman showed a low affinity binding and did not compete for 3H-cortisol or 3H-DHT binding sites in plasma. 14C-centchroman binding protein was heat stable in nature and showed the electrophoretic pattern similar to that of albumin (Rf 0.70). Thus centchroman binds to albumin in monkey plasma which can be suggested as carrier protein for this contraceptive agent.

Animals↗

Effect of centchroman on tubal transport and preimplantation embryonic development in rats.

A single oral administration of centchroman (1.25 mg/kg) to adult female rats within 24 h of mating induced slight acceleration in the rate of transport of embryos through the oviducts. The compound did not seem to produce any deleterious effect on preimplantation embryonic development since well organized and apparently normal embryos were collected from the genital tract up to Day 12 of pregnancy. The recovery rate of embryos from centchroman-treated rats was, however, significantly reduced after Day 4 of pregnancy. There was some stimulation in the rate of cleavage of embryos and morula to blastocyst transformation, but retardation in the shedding of the zona pellucida. The rate of blastocyst formation was not altered when 6-8-cell embryos collected from the oviducts of control rats were transferred to the uteri of control or centchroman-treated females. A delay in zona shedding was observed in the centchroman-treated recipients.

Animals↗