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After having unprotected sex, a woman may use a medication called Plan B to help prevent pregnancy. This emergency contraceptive is available without a prescription for women of all ages. It comes in two forms -- one that is taken in a single dose and one that is taken as two doses. Side effects include nausea, headaches, and fatigue.

What Is Plan B?

Plan B One-Step™ (levonorgestrel) is a medication that is an emergency contraceptive, which is used to prevent pregnancy after unprotected sex. Originally, it was a prescription medication. However, it is now available without a prescription to all women (even those under 18 years of age).

Plan B originally came in a two-step formulation, which consisted of two tablets that are taken 12 hours apart. However, it was replaced by a new formulation, Plan B One-Step, which consists of one tablet. The old formulation is still available in generic form.

(Click Plan B Uses for more information, including possible off-label uses.)

Who Makes Plan B?

The medication is made by Gedeon Richter, Ltd., for Duramed Pharmaceuticals, Inc., a division of Barr Pharmaceuticals, Inc. (now owned by Teva Women's Health, Inc).

How Does It Work?

Plan B contains a high dose of levonorgestrel, a progesterone-type hormone that is used in many birth control pills. It prevents pregnancy primarily by stopping ovulation (the maturation and release of eggs from the ovaries) or by preventing fertilization of the egg if ovulation has already occurred. It also alters the lining of the uterus (the endometrium), making it less receptive to a fertilized egg. If a fertilized egg has already implanted into the uterus, Plan B will not cause an abortion.
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Last reviewed by: Kristi Monson, PharmD;
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