Is Opill As Effective As Other Birth Control Pills?
In our latest question and answer, the pharmacist discusses the effectiveness of Opill, an over-the-counter progestin-only pill.
I think it's great that Opill was approved and is going to be over the counter. and is going to be over the counter. However, I heard it may not be as effective as other birth control pills. Is this true?
Jul 13, 2023- Opill is about 98% effective at preventing pregnancy when taken correctly but requires strict daily timing with little room for missed or late doses. Opill works differently than combination birth control pills by thickening cervical mucus and thinning the uterus lining rather than consistently stopping ovulation. Irregular bleeding and menstrual changes are common side effects with Opill that may lead some people to stop using it.
Quick Answer
Opill, a progestin-only pill, is approximately 98% effective in preventing pregnancy but is less forgiving in terms of missed or late doses compared to combined hormone birth control pills (i.e., those that contain both progestin and estrogen).
Detailed Answer
Opill is a progestin-only pill, also known as a mini pill or POP (progestin-only pill). Unlike combined hormone pills that contain both estrogen and progestin, progestin-only pills only contain progestin and do not include estrogen.
Progestin-only pills like Opill primarily work by thickening the cervical mucus, making it difficult for sperm to reach the egg. They also thin the lining of the uterus, reducing its receptiveness to implantation. These mechanisms help prevent pregnancy. Some progestin-only pills suppress ovulation, but most do not.
Most sources report that when taken correctly, progestin-only pills are around 99% effective in preventing pregnancy.
Clinical trials for Opill specifically, involving more than 2,000 women aged 15 to 49 years old (over 21,000 28-day cycles), reported a pregnancy rate of 2 percent, indicating an effectiveness rate of around 98% in preventing pregnancy.
Effective But Less Margin For Error
Progestin-only pills, like Opill, can be highly effective in preventing pregnancy when taken correctly. However, they have a narrower margin for error compared to combined hormone pills.
Progestin-only pills require strict adherence to a daily dosing schedule. Deviating from the recommended timing, even by a few hours, or missing doses completely, can significantly decrease their effectiveness.
In contrast, combined hormone pills are generally more forgiving if a pill is missed or taken slightly outside the designated time window. However, it is still important to follow the instructions provided with any birth control pill to maximize its effectiveness.
Other Differences Versus Combined Hormone Pills
There are a few notable differences between progestin-only pills, like Opill, and birth control pills that contain both estrogen and progestin I want to point out here (in addition to the fact that progestin-only pills are less forgiving with missed doses):
- In contrast with estrogen-progestin oral contraceptive pills, most progestin-only pills do not consistently suppress ovulation. The effectiveness of progestin-only pills in preventing pregnancy primarily relies on their effects on cervical mucus and the endometrium.
- Unscheduled bleeding (e.g., spotting, breakthrough bleeding) and menstrual changes are fairly common in progestin-only pill (POP) users. In fact, menstrual irregularities are a common reason for discontinuation of progestin-only pills.
Final Words
Opill, as a progestin-only pill, is an effective birth control option with an approximately 98% success rate in preventing pregnancy.
Although you don't need a prescription for Opill, if you have concerns or questions about taking it, I recommend you speak with your doctor for personalized advice.
References & sources
Glossary — Terms in This Answer
- Progestin
- A synthetic hormone that prevents pregnancy by thickening cervical mucus and thinning the uterus lining.
- Estrogen
- A naturally occurring hormone that, when combined with progestin in birth control pills, makes them more forgiving of missed doses.
- Cervical mucus
- A fluid in the cervix that progestin-only pills thicken to block sperm from reaching the egg.
- Ovulation
- The release of an egg from the ovary; most progestin-only pills do not prevent this process.
- Endometrium
- The lining of the uterus, which progestin-only pills thin to make implantation of a fertilized egg less likely.
- Breakthrough bleeding
- Unscheduled vaginal bleeding or spotting that can occur in users of progestin-only pills.
- Implantation
- The process where a fertilized egg attaches to the uterus lining; progestin-only pills reduce the likelihood of this occurring.
- Menstrual irregularities
- Changes in menstrual bleeding patterns, such as spotting or missed periods, that are common side effects of progestin-only pills.
Dr. Brian Staiger, PharmD
Doctor of Pharmacy, board certified clinical pharmacist (BCPS), American Herbalist Guild, Medication Therapy Management certified
Brian Staiger, PharmD, BCPS, is a licensed pharmacist with more than 13 years of experience across retail pharmacy, clinical pharmacy, medication safety, pharmacy program development, and healthcare administration. He is the founder of HelloPharmacist.com, where he helps patients...
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