Family Planning Plus

I’m sorry, but without the name and dosage of the medication that you used after the morning after pill, it’s difficult to give you a clear answer. It would be best to contact the medical provider who prescribed this medication to see if it would interfere with the effectiveness of the morning after pill.

That being said, the following description regarding possible drug interactions can be found at www.rxlist.com. “Theoretically, the effectiveness of low-dose progestin-only pills (including the morning after pill) is reduced by hepatic enzyme-inducing drugs such as the anticonvulsants phenytoin, carbamazepine, and barbiturates, and the antituberculosis drug rifampin. No significant interaction has been found with broad-spectrum antibiotics. It is not known whether the efficacy of Plan B® (levonorgestrel) would be affected by these or any other medications.”

Plan B and other morning after pills are not 100% effective. They reduce the risk of pregnancy by delaying ovulation and possibly by interfering with fertilization and implantation. They work best when they are used within the first 24 hours after unprotected sex but can be used up to 72 hours (or three days) after the unprotected sex.  Some research has shown that the morning after pill may even have some preventive effects up to 120 hours (five days) after unprotected sex.  The sooner you use Plan B, the more effective it is.

Plan B should not be used as a regular method of birth control as it is less effective than other methods.  If you are going to continue to have sexual intercourse, you may want to think about using a regular form of birth control.  Please contact one of our offices for an appointment to discuss your contraceptive options. If you live too far away, contact the Family Planning or Planned Parenthood office closest to you.