What Antibiotics Make Birth Control Ineffective?

Birth control pills allow a woman to control when and if she gets pregnant, while still being intimate with her partner. However, there are some antibiotics that can make birth control less effective.

Significance

• If you are taking antibiotics that interfere with your birth control pills, this can raise the chance of pregnancy for you. You may still have some protection, but not complete protection.

List

• Rifampin is the antibiotic that will interfere the most with a woman's birth control pills. Other antibiotics that will interfere to a lesser degree include ampicillin, sulfamethoxazole, nitrofurantoin, penicillin, tetracycline and amoxicillin.

Identification

• If you notice pink or brown blood (known as spotting) and your period is not due for another week or two, your antibiotics may be interfering with your birth control. This is the first, and possibly only, physical sign you will notice.

Prevention/Solution

• There are ways you can reduce the chance of pregnancy while you are taking antibiotics. Alternative pregnancy prevention measures include the use of condoms, spermicide, diaphragm or abstinence.

Warning

• Antibiotics can continue to interfere with your birth control pills for at least one week after you stop taking them, so it is important to continue alternative prevention measures during this time. You should ask your doctor if you need to use alternate measures longer than this.