Sally asked
Tomorrow, I am taking the last two doses of Cipro for my kidney infection. I should also start my new pack of birth control (tri-nessa). Should I use a back up method and for how long? Thank you!
At a glance
- Certain antibiotics, such as 'rifamycin' antibiotics, are well-known to decrease birth control concentrations.
- Cipro (ciprofloxacin) is not a rifamycin antibiotic, and isn't thought to reduce the effectiveness of birth control for most individuals.
- Nevertheless, a small percentage of people may be affected and therefore, as a safety precaution, the use of back-up contraception may be prudent.
Answer
Most antibiotics are not thought to interact significantly with birth control pills.
There are certain antibiotics that are exceptions to this though, including the "rifamycin" family of antibiotics.
These antibiotics can significantly increase how fast we metabolize the hormones in birth control pills, decreasing effectiveness.
When it comes to Cipro (ciprofloxacin), most available data indicates that it will not affect your birth control pill and should not put you at an increased risk of pregnancy.
However, a few studies have noted that a very small percentage of individuals may experience significant drops in hormone concentrations with antibiotics for reasons not entirely understood.
As the consequences of unplanned pregnancy are great, it generally is a good idea to use back-up contraception, such as condoms, while taking antibiotics like Cipro.
We discuss the details regarding this below.
How Can Cipro Affect Birth Control Pills?
As we know, antibiotics kill bacteria. Unfortunately, they also get rid of some of the "normal bacterial flora" in our gastrointestinal tract. The bacteria in our gut is very important for many bodily functions, including in the metabolism of hormones from birth control pills.
The bacteria in our gut is responsible for what is known as estrogen enterohepatic recirculation. In simple terms:
- The estrogen from birth control pills is metabolized in the liver.
- Some of this metabolized estrogen is released back into the gut.
- The bacteria in our gut turn the metabolized estrogen back into active estrogen, which we then re-absorb.
If we reduce the bacteria in our gut, theoretically, there will be less estrogen to absorb, decreasing concentrations, and potentially decreasing how well birth control works.
Nevertheless, most studies on the matter state that the amount of estrogen lost from a reduction from GI bacteria is minimal and will not significantly affect birth control pills.
Recommendations
While most studies show that Cipro will not affect your birth control, the concern comes from data showing that a very small number of individuals do appear to be affected. Per one study:
References
- Drug interactions between oral contraceptives and antibiotics. ScienceDirect
- Updated Clinical Guideline Published: Drug Interaction with Hormonal Contraception. FSRH
