Proprietary drug and Patent medicine

Proprietary drug noun - A drug that has a trade name and is protected by a patent (can be produced and sold only by the company holding the patent).

Patent medicine and proprietary drug are semantically related In some cases you can use "Patent medicine" instead a noun phrase "Proprietary drug".

Patent medicine noun - Medicine that is protected by a patent and available without a doctor's prescription.

Proprietary drug and patent medicine are semantically related in proprietary medicine topic. You can use "Proprietary drug" instead a noun phrase "Patent medicine".