A Practice Note discussing the antitrust issues that arise in managing the pharmaceutical supply chain, specifically from the use of restricted distribution systems, either voluntarily or under Food and Drug Administration (FDA) mandate, including risk evaluation and mitigation strategy (REMS) programs. This Practice Note discusses the potential for restricted distribution and REMS programs to raise antitrust concerns by delaying or preventing generic drugs from entering the market, including by preventing participation in a single, shared REMS (SSRS) program. It also addresses relevant laws, enforcement and advocacy by the Federal Trade Commission (FTC) and FDA, and pending legislation.