The FDA has issued a warning letter to Amazon for distributing products that contain undeclared and potentially harmful active pharmaceutical ingredients. The products in question are marketed as energy-enhancing supplements or food, but laboratory analyses confirmed that they contain sildenafil or tadalafil, which are prescription drugs used to treat erectile dysfunction. Amazon is responsible for introducing or delivering these products into interstate commerce, which is prohibited under the Federal Food, Drug, and Cosmetic Act. The FDA has requested that Amazon take steps to address these violations and prevent their recurrence.