Which of the following best describes a nonproprietary drug?

A nonproprietary drug is best described as one that is generally sold without a patent. This means that the drug is not associated with a specific brand name or proprietary formulation, allowing it to be produced and marketed by multiple manufacturers. This characteristic often leads to the availability of generic versions of the drug, which can be sold at lower prices compared to brand-name medications.

When a drug is available without a patent, it means that the exclusive rights to produce that drug have expired, allowing generic manufacturers to replicate the drug’s formulation. This promotes competition in the pharmaceutical market and can lead to cost savings for consumers.

The other options reflect specific conditions or classifications of drugs but do not define the nonproprietary nature. For instance, drugs available at limited pharmacies or those requiring a prescription may still be proprietary, while drugs containing controlled substances can be either proprietary or nonproprietary depending on their patent status. Hence, identifying a nonproprietary drug focuses specifically on the absence of a patent, distinguishing it clearly from proprietary drugs.