Jaclyn Kinkade, a 23-year-old doctor's-office receptionist and occasional model, was a casualty of America's No. 1 drug menace when she overdosed and died, alone, in a tumbledown clapboard house in Dunnellon, Fla.

The drugs that killed her didn't come from the Colombian jungles or an Afghan poppy field. Two of the three drugs found in her system were sold to Ms. Kinkade, legally, at Walgreen Co. and CVS Caremark shops, the two biggest U.S. pharmacies. Both prescription drugs found in her body were...