Morning-after pill: Quick facts

NAME: Plan B.

MANUFACTURER: A subsidiary of Teva Pharmaceuticals Inc.

USE: If taken within 72 hours of unprotected sex, it can lower the risk of pregnancy by up to 89 percent.

WHAT IT IS: A high dose of a drug found in many regular birth-control pills.

WHAT IT ISN'T: It's not the same as the abortion pill RU-486. Plan B prevents ovulation or fertilization of an egg; it also may prevent the egg from implanting into the uterus, though recent research suggests that's unlikely. It has no effect on women who already are pregnant.

WHAT ELSE IT ISN'T: Everyday contraception. It's not intended for routine use.

WHO CAN BUY IT: Starting soon, women 17 and older can buy it without a prescription. Currently, they must be 18 for nonprescription sale. Anyone younger still requires a prescription.

SIDE EFFECTS: Some nausea, dizziness, breast tenderness, temporary menstrual changes.