Xtina asked
I was prescribed antibiotics which are known to make hormonal birth control pills less effective. I am supposed to use a backup method for 7 days after completing the antibiotics. When I finish my antibiotics I will have 3 days left of bcp and then 7 placebo pills. Do I need to wait 7 days into my next pack? Or is 3 hormonal and 4 placebo OK?
Answer
Taking a course of antibiotics while also using birth control can be a very concerning situation for women. We want to protect against the serious consequence of unplanned pregnancy as well as prevent unwanted adverse events that may result from an altered level of hormones, such as spotting and bleeding.
The jury is still out on just how much most antibiotics affect birth control.
Studies have shown that most antibiotics do not significantly reduce the concentrations of oral contraceptives in the body and the efficacy of birth control pills is unchanged.
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.
On the other hard, 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.
In addition, 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.
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.
In terms of how long to use a backup method, it is most often recommended to use the backup method for 7 consecutive days of ACTIVE pills. This is the usual recommendation in patients that could potentially experience changes in how their bodies absorb and metabolize their birth control pills. Digestion issues, vomiting, diarrhea, and antibiotic use are all common reasons this could happen.
In your situation, make sure you use back up contraception for 7 active pills in row, from your new pack.
Be sure to speak with your doctor regarding your concerns as well.
