The Trump administration has made lowering drug prices one of its top priorities, and last week it unveiled a proposal that could vastly rewrite the way drugs are sold in the United States.

The proposal takes aim at the secret deals that drug companies strike with pharmacy benefit managers, the industry intermediaries that negotiate the price of drugs for insurers and large employers.

These after-the-fact discounts, called rebates, have come under harsh criticism and are blamed for helping to push up the list price of drugs, which consumers are increasingly responsible for paying.

Under the proposed rule, released on Thursday, pharmacy benefit managers would lose the legal protections that allow them to accept rebates from drug companies for brand-name drugs covered under the Medicaid and Medicare government programs. Any such discounts would instead have to be credited at the pharmacy counter when patients fill a prescription.