The U.S. Food and Drug Administration has approved the first generic version of the emergency contraceptive Plan B (levonorgestrel) tablets, in the 0.75 mg dosage. The generic product will be available by prescription only for women ages 17 and under.

Plan B was first approved in 1999 for prescription use only for women of all ages. Plan B is manufactured by Duramed Pharmaceuticals Inc., of Cincinnati.

In 2006, Plan B was approved for nonprescription use for women ages 18 and older. Plan B remained available as a prescription-only product for women ages 17 and under.

The new approval allows marketing of a prescription-only generic product for women ages 17 and under. No generic levonorgestrel product for emergency contraception can be approved for nonprescription use in women ages 18 and older until Aug. 24, 2009, when the marketing exclusivity held by Duramed for the nonprescription use expires.

The generic levonorgestrel tablets 0.75 mg are made by Watson Laboratories Inc., based in Corona, Calif.

Levonorgestrel can prevent pregnancy after unprotected intercourse or a known or suspected contraceptive failure. It is not effective in terminating an existing pregnancy and does not protect against sexually transmitted diseases, including HIV infection.

The drug delivers a surge of hormones, similar to a high dose of birth-control pills, interfering with fertilization and preventing implanation of a new embryo in the uterus. Most medical authorities do not consider this to be an abortion but some anti-abortion groups disagree.

Plan B is not the same as mifepristone, sometimes called RU-486, a pill that chemically induces an abortion.

Even when it was available only with a prescription, Plan B was not widely available in some areas. For example. Wal-Mart did not stock it in its pharmacies until March 2006, when it succumbed to pressure from Illinois, Massachusetts, Connecticut and other states.

Three Massachusetts women had sued Wal-Mart for not carrying the pill, leading to the state Board of Pharmacy's decision to require the chain to stock the drug.."