Method of action
Ormeloxifene is a SERM, or selective estrogen receptor modulator. In some parts of the body, its action is estrogenic (e.g, bones), in other parts of the body, its action is anti-estrogenic (e.g., uterus, breasts (Gara et al., 2007)It causes an asynchrony in the menstrual cycle between ovulation and the development of the uterine lining, although its exact mode of action is not well defined. In clinical trials, it caused ovulation to occur later than it normally would in some women (Singh 2001), but did not affect ovulation in the majority of women, while causing the lining of the uterus to build more slowly. It speeds the transport of any fertilized egg through the fallopian tubes more quickly than is normal (Singh 2001). Presumably, this combination of effects creates an environment such that if fertilization occurs, implantation will not be possible.
Usage
Ormeloxifene may be used as a contraceptive or as a treatment for dysfunctional uterine bleeding.
As birth control
Ormeloxifene may be used as a weekly oral contraceptive. This is touted as a major advantage by its developer and its manufacturer. Hormonal birth control pills should be taken at approximately the same time each day. In the case of progestogen only pills other than Cerazette that do not consistently inhibit ovulation, a delay of as little as three hours can increase the risk of pregnancy because of the limited duration of their effect on the cervical mucus. Ormeloxifene's weekly schedule is an advantage for women who prefer an oral contraceptive, but find it difficult or impractical to adhere to a daily schedule.
For the first twelve weeks of use, it is advised to take the ormeloxifene pill twice per week. From the thirteenth week on, it is taken once per week. The consensus is that backup protection in the first month is a cautious but sensible choice. A standard dose is 30mg weekly, but 60mg loading doses can reduce pregnancy rates by 38%.
Effectiveness
One Phase III multicenter trial of ormeloxifene 30 mg weekly by 898 women for an average of 15 months found a method failure Pearl Index of 2.84.
A second Phase III multicenter trial of ormeloxifene 30 mg twice-a-week for 3 months followed by 30 mg weekly by 376 women for an average of 10.5 months found a method failure Pearl Index of 1.83 and a 12-month life-table method failure pregnancy rate of 1.63% ± 0.74%.
