Young, Assured and Playing Pharmacist to Friends - New York Times:

A spokeswoman for the Drug Enforcement Administration says it is illegal to give prescription medication to another person, although it is questionable whether the offense would be prosecuted.

While it may be true that the feds won't prosecute you (unless you're dealing in narcotic prescriptions), the state authorities will quite happily toss you in the clink for practicing medicine without a license.

Update: link fixed