Oral contraceptives (birth control pills) work by having hormones in them that:
stop your ovaries from releasing eggs
make the lining of your uterus thinner, so eggs fertilized by a man’s sperm can not attach to your uterus; or
make it harder for sperm to get to your eggs.
These hormones are called estrogens and progestins.
Some antibiotics make it hard for your body to absorb the hormones in your birth control pills. Other antibiotics make your body get rid of the hormones faster. If either happens, the lower levels of hormones in your body may allow you to get pregnant when you do not want to. Antibiotics that may do this include:
rifampin;
penicillins, such as penicillin, ampicillin and amoxicillin;
tetracylines, such as tetracyline, minocycline and doxycycline;
co-trimoxazale (trimethoprim and sulfamethoxazole WHERE id =
trimethoprim; and
others.
Other drugs may also make your birth control pills NOT work.
NOTE: Antibiotics, except for rifampin, will not affect contraceptive implants. An implant is a capsule inserted under the skin on the inside of a woman’s upper arm. It reduces the chance of becoming pregnant by releasing progestin into your bloodstream.
If you have a progestin implant and are taking rifampin, you should use another form of birth control as shown on the back of this fact sheet.
Always tell your doctor you are on birth control pills. Your doctor can advise you on possible drug interactions.
Check with your pharmacist before you take any medications or herbal products.
When you have to take prescription drugs, keep taking your birth control pills (unless your doctor tells you not to) BUT also use a barrier form of birth control. You can use:
a condom;
a diaphragm; or
a cervical cap.
If you use a barrier form of birth control as well as the pill when you are taking antibiotics, you will reduce the risk of getting pregnant by accident.
Continue to use the barrier form of birth control for two weeks after you finish the antibiotics.
Your fetus will not be affected if you become pregnant while you are taking birth control pills and antibiotics.
For further information on how to prevent yourself from getting pregnant while taking prescription drugs, or further information about oral contraceptives, ask your doctor, public health nurse or pharmacist, or contact your local Planned Parenthood office.