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.

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.

Interaction with anti-implantation and estrogen antagonistic activities of dl-ormeloxifene, a selective estrogen receptor modulator, by tetracycline in female Sprague-Dawley rats

Among the 10 commonly used therapeutic agents investigated, concurrent oral administration of tetracycline (140 mg/kg) twice daily on Days 1-5 post-coitum (pc) interfered with the post-coital anti-implantation activity and almost completely abolished estrogen antagonistic activity of the single anti-implantation (1.5 mg/kg, orally) dose of dl-ormeloxifene administered on Day 1 pc, resulting in the occurrence of resorbed implantations in 50% of the females. However, no such interaction was evident when tetracycline was administered intramuscularly or when ormeloxifene was administered at twice its anti-implantation dose. There was no effect of ormeloxifene and/or tetracycline treatment on serum estradiol and progesterone levels, and all animals presented apparently normal corpora lutea. Ormeloxifene administered per se inhibited aminopyrine-N-demethylase (AD), glucose-6-phosphate dehydrogenase (G-6-PDH) and glutathione-S-transferase (GST) in the liver on the day of maximal endometrial receptivity, which was prevented by tetracycline co-administration. Aniline hydroxylase and AD were not detected in small intestine or uterus in vehicle control or any of the treatment groups. There was, however, no effect of ormeloxifene plus tetracycline treatment on serum total alkaline phosphatase activity. Findings suggest that interference with anti-implantation action of ormeloxifene by tetracycline might be due primarily to the almost complete abolition of its estrogen antagonistic activity at the uterine level, effected by decreased bioavailability of ormeloxifene and/or its active metabolite(s) by altered enterohepatic recirculation because of the effect on gut microflora. This might alternatively be related to an increased rate of its metabolism and elimination from the system via prevention of ormeloxifene-induced inhibition of hepatic AD, G-6-PDH, and GST, which, by effecting a decreased rate of metabolism, might be responsible for prolonged (approximately 120 h) duration of estrogen antagonistic/anti-implantation action of ormeloxifene in this 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.

Simultaneous liquid chromatographic determination of centchroman and its 7-demethylated metabolite in serum and milk

A precise and sensitive high-performance liquid chromatographic assay was developed and validated for determination of centchroman (I) and its 7-demethylated metabolite (II) in human serum and milk. The serum, at alkaline pH, was extracted with diethyl ether. In the case of milk, after precipitation of the milk protein with acetonitrile, the supernatant was evaporated to dryness and then extracted with diethyl ether at alkaline pH. After solvent evaporation the residue was reconstituted in mobile phase. Separations were accomplished by reversed-phase liquid chromatography using a Spheri-5 cyano column. Recoveries of I and II were always > 95%. Excellent linear relationships (r > 0.999) were obtained between the measured and added concentration ratios of the corresponding serum and milk concentrations over a range of 1 to 1000 ng/ml and 2.5 to 1000 ng/ml for I and II, respectively.