New research sheds light on the use of over-the-counter birth control pills

February 22, 2011 — Women who obtain oral contraceptives over the counter in Mexico are likely to stay on the birth control pill longer than those who obtain pills by prescription at US clinics, according to a study by researchers from two University of Texas campuses, Ibis Reproductive Health, and New York University.

The study was led by Joseph Potter, professor in the Sociology Department and Population Research Center at The University of Texas at Austin.

The Border Contraceptive Access Study takes advantage of a natural experiment along the US-Mexico border, where US women have the option of obtaining oral contraceptives over the counter in Mexico, and it provides insight into what might happen if the pill were made available OTC throughout the US. The researchers interviewed more than 1,000 El Paso, Texas oral contraceptive users and followed them over nine months. Half of the women obtained their pills over the counter at pharmacies in Juarez, Mexico, while the other half obtained them from family planning clinics in El Paso. Most women in the study were low-income and uninsured.

According to the findings, women who obtained pills in El Paso clinics were 60% more likely to stop taking their pills during the nine-month study compared to those who purchased their contraceptives without a prescription in Mexico. Women who received fewer than six packs of pills at one time at the clinic were about 80% more likely to discontinue taking the pill compared to over-the-counter users. 

The results suggest that access is a key determinant of contraceptive continuation. “Removing unnecessary barriers to access—such as limits on the number of pill packs dispensed or even possibly the prescription requirement—could have an important impact on reducing unintended pregnancy,” Potter says.

In a related paper from the Border Contraceptive Access Study, the researchers found that women who purchased their pills over the counter in Mexico might not be making the best choice about which kind of birth control is safest for them.

The study, led by Daniel Grossman of Ibis Reproductive Health, found that women who obtained combined oral contraceptives, which contain both synthetic estrogen and progesterone, in Mexico were significantly more likely than US clinic users to have health conditions such as hypertension or smoking over age 34 that may put them at risk while using this type of pill.

While there was no difference in absolute contraindications, relative contraindications were significantly more common among over-the-counter users (13%) compared to clinic users (9%). Although no woman in the study reported a medical complication related to pill use, these contraindications may put women at higher risk of having a heart attack or stroke while using estrogen-containing pills.

The findings highlight the importance of self-screening for contraindications when pills are made available over the counter, said Grossman, who also coordinates a working group of researchers, clinicians, and advocates exploring the feasibility of an OTC switch for pills in the US.

“If combined oral contraceptives are available over the counter, we need to be sure that women have the necessary tools to determine whether they are appropriate for this kind of pill,” Grossman said. “Alternatively, progestin-only pills, which don’t contain estrogen, might be the best option as the first over-the-counter oral contraceptive in the US.  Progestin-only pills are also very effective, but they have many fewer and rarer side effects.”

The Border Contraceptive Access Study is funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development. The findings will be published in the March issue of Obstetrics & Gynecology.