Prescription Drug Fairness Act - Amends the Clayton Act to deem: (1) the sale of a prescription drug by a manufacturer outside the United States to be the sale of such drug within the United States for purposes of provisions prohibiting price discrimination; and (2) discrimination in price between wholesalers within the United States and wholesalers outside the United States substantially to injure, destroy, or prevent competition with any person who either grants or knowingly receives the benefit of such discrimination, or with customers of either of them.