Which act regulates the prohibition of drug samples and reselling?

The Prescription Drug Marketing Act (PDMA) is the correct response because it was enacted to prohibit the diversion of prescription drugs from legitimate commercial channels. Specifically, it establishes regulations regarding the distribution of drug samples and prohibits the resale of these samples. The PDMA aims to ensure that drug samples are used only for their intended purpose, which is to promote the adequate distribution and proper utilization of prescription drugs.

By imposing restrictions on drug samples and preventing their resale, the PDMA helps to mitigate issues related to counterfeit medications and ensures that the integrity of the drug distribution system is maintained. It mandates that drug manufacturers must adhere to certain procedures regarding the distribution of samples, which prevents them from being sold or exchanged inappropriately.

The other options do not address the prohibition of drug samples and reselling in the same manner. The Orphan Drug Act is focused on providing incentives for the development of drugs for rare diseases. The Durham-Humphrey Act primarily deals with the distinction between prescription and over-the-counter medications. The DHA amendment relates to specific amendments regarding drug approval but does not focus on the issues of drug samples and reselling. Thus, the PDMA is the most relevant legislation regarding the concerns outlined in the question.