Birth control pills using a 24-day regimen -- 24 days of active pills and four days of inactive pills -- are becoming more popular. A new study suggests that the shorter drug-free interval combined with pills containing drospirenone, a specific type of progestin that tends to remain in the body longer, are better at preventing pregnancy.
German researchers examined a database of 52,218 U.S. women using oral contraceptives to look at what types of pills the women were using and the failure rates, meaning that an unintended pregnancy occurred. The study found that women on a 24-day regimen containing drospirenone had lower failure rates compared with the standard 21-day regimen of pills containing other types of progestins: a 2.1% failure rate after one year of use compared with 3.5% for the other pills and a 4.7% failure rate after three years compared with 6.7%.
The pills Yaz and Yasmin contain drospirenone and have become popular products because this progestin is thought to be more natural than other forms. However, the pills have also led to numerous lawsuits in the United States among women who said they suffered serious side effects. Bayer, the maker of Yaz and Yasmin, funded the new study, which is published in the January issue of Obstetrics & Gynecology.
Misuse of oral contraceptives, such as missed pills, accounted for most of the unintended pregnancies in the study, the authors noted. Under "perfect use," oral contraceptives result in unintended pregnancy rates of as low as 0.3%. In real life, failure rates are closer to 8%.
"Our study indicates that shortening of the pill-free interval improves real-life effectiveness of oral contraceptives," said the lead author of the study, Dr. Juergen Dinger, of the ZEG - Berlin Center for Epidemiology and Health Research, in an e-mail. Adding a progestin with a long half-life -- the time it takes for a substance to lose half of its pharmacologic activity -- appears to extend that protection.
But, she added, "progestins have complex pharmacological profiles." Different types of progestins may benefit women who have other needs than just pregnancy protection, such as acne, endometriosis, bleeding disorders and other conditions.
Moreover, Dinger said, "specific regimens, progestins and estrogens might be associated with specific safety profiles. I strongly believe that prescribing physicians and women needing contraception have to 'customize' the contraceptive approach" based on the woman's likelihood of complying with daily pill use (younger women have more compliance problems) and the need to address other conditions.
Since their inception, birth control pills have become increasingly safer -- and yet more complex and targeted for conditions other than pregnancy prevention. These days, choosing which pill to take warrants a fairly thorough discussion between a woman and her doctor.
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