Mackenz asked
Hello! Today I was prescribed amoxicillin for strep throat, and I heard it interferes with birth control. I’m on Nuvaring and I honestly do use it in the perfect percentile range, never missing a beat, and I have not had sexual intercourse for 2 weeks.I’m not going to have sex while on antibiotics, and I was wondering, to keep my chances of something going wrong, should I still abstain for a bit after I’m off of the 10 day antibiotic cycle? If yes, for how long? Thank you! Have a good day!
Answer
Amoxicillin, when taken by mouth, may interfere with birth control and make it less effective. As such, the risk of unwanted pregnancy may be increased if you take amoxicillin and are on birth control pills or other forms hormonal contraception such as the Nuvaring.
Amoxicillin - Birth Control Interaction
Antibiotics are known to cause changes to our normal bacterial gut flora. This could theoretically affect how estrogen and progestin from birth control pills are metabolized since our gut bacteria are involved in how our bodies process these hormones. This change in gut flora could potentially decrease the concentrations of the hormones in oral contraceptives, ultimately leading to spotting and a loss of contraceptive efficacy.
However, the only antibiotics that have a definitive and well documented negative effect on oral contraceptive levels, based on the data we have, are ones from the rifamycin family of antibiotics such as rifampin. There is conflucting evidence in regard to other classes of antibitoics.
There are studies that note that there are a small number of individual patients who do in fact experience a significant decrease in concentrations of oral contraceptives when taking antibiotics and appear to ovulate (which birth control pills are supposed to suppress). The problem is that it is difficult to identify exactly who is susceptible.
Amoxicillin - Nuvaring Interaction
In regard to Nuvaring specifically, most studies conclude that antibiotics do NOT decrease hormone concentrations in those using the Nuvaring vaginal contraceptive. The lack of the interaction is most likely due to the fact that the hormones in Nuvaring are absorbed vaginally, and avoid metabolism through the gut and liver.
A few studies have confirmed findings that antibiotics don't appear to affect Nuvaring. In one study, women were placed into one of two groups:
- NuvaRing alone for 21 days
- NuvaRing for 21 days plus amoxicillin on for 10 days
The results of the study showed that there were no differences in hormone concentrations between those using Nuvaring alone versus those using it with the antibiotic. Other studies have shown the same results.
Recommendation
Overall, the general consensus appears to be that most antibiotics do not pose a problem in those on birth control BUT women who may be affected are not easily identified and the true number of incidences of pregnancy while on antibiotics may be under-reported in total. Since unplanned pregnancy has major consequences, it may be prudent to use an additional method of contraception during short-term antibiotic use, just to be safe.
Therefore, some sources recommend that alternative contraception is used while taking the antibiotic and for at least one week after the last dose of a short term antibiotic regimen. It is recommended to use condoms with the Nuvaring to prevent sexually transmitted diseases and is a good option as an alternative contraceptive.
