Centchroman is a non-steroidal, once-a-week oral contraceptive and a selective estrogen receptor modulator (SERM) developed in India. It is a unique post-coital contraceptive with anti-estrogenic and weak estrogenic properties, primarily used for birth control and management of dysfunctional uterine bleeding. It is known for its high efficacy, good tolerability, and the advantage of not interfering with the normal menstrual cycle in most users.
Adult: **Contraception:** Loading dose: 30 mg twice a week for first 12 weeks. Maintenance: 30 mg once a week, preferably on the same day. **Dysfunctional Uterine Bleeding:** 30 mg twice a week until bleeding stops, then 30 mg once a week for at least 3 months.
Note: Take after meals with a full glass of water to improve tolerance. For contraception, the first dose should be taken on the first day of menstruation. If a weekly dose is missed, take it as soon as remembered and continue the next dose on the scheduled day. If the delay is more than 3 days, use a barrier method for the next 7 days.
Centchroman acts as a competitive antagonist of estradiol at the estrogen receptors in the reproductive tract (uterus, cervix, vagina). Its primary contraceptive action is by preventing embryo implantation. It alters the endometrial milieu, making it unreceptive for implantation by accelerating endometrial maturation and causing premature secretory changes. It also increases the viscosity of cervical mucus, hindering sperm penetration.
Pregnancy: **Pregnancy Category: Not Assigned (Contraindicated).** Teratogenic risk unknown. Must be ruled out before initiation. If pregnancy occurs while on therapy, discontinue immediately.
Driving: May cause dizziness or visual disturbances. Caution advised while driving or operating machinery until response is known.
| Rifampicin | Induces CYP3A4, reducing Centchroman plasma levels, leading to contraceptive failure. | Major |
| Phenytoin, Carbamazepine, Phenobarbital | Enzyme inducers; decrease Centchroman efficacy. | Major |
| Ketoconazole, Itraconazole, Erythromycin | CYP3A4 inhibitors; may increase Centchroman levels and side effects. | Moderate |
| Warfarin | Centchroman may alter anticoagulant effect; monitor INR closely. | Moderate |
| Thyroid Hormones | Centchroman may increase serum bound thyroxine levels. | Moderate |