When did merck's patent on zocor simvastatin expire?

Merck’s “Zocor” drug‑product patent, the one that kept generic simvastatin off the U.S. market, expired on January 1, 2000 – the date on which the first U.S. generic simvastatin was approved and made commercially available.

The underlying active‑ingredient patent (U.S. Pat. 4,784,123, issued December 4, 1989) had a 17‑year term from its issue date, so that patent expired in 2006. The product patent’s expiration in 2000 is the key event that allowed generics to enter the market.