You should be ok, if your supply is less than 3 months usage.

U.S. Customs has really been particulary aggressive since last Spring to people who are carrying (or shipping) perscription drugs into the U.S. (Even Rush Limbaugh ran into this)

Nobody is quite sure what caused this sudden enforcement surge by U.S. Customs about their stated "concern about the safety of pharmacuticals purchased overseas". Although, it is widely speculated that the U.S. Perscription Drug Bill for Seniors had failed to achieved "sign-up" goals. So, the Feds decided to limit the supply of foreign drugs, and thereby frighten seniors into signing-up.

In essence, the U.S. Customs was acting as the enforcement arm of the American pharmacutical industry, to insure maximum profitablility.

Nevertheless, the Congress forced Customs to suspend this practice if they wanted their 2007 Appropriations. So, about two months ago, the border harassment stopped.