A patent medicine is a non-prescription medicine or medicinal preparation that is typically protected and advertised by a trademark and trade name, and claimed to be effective against minor disorders and symptoms, as opposed to a prescription drug that could be obtained only through a pharmacist, usually with a doctor's prescription, and whose composition was openly disclosed. Many over-the-counter medicines were once ethical drugs obtainable only by prescription, and thus are not patent medicines.

A charlatan is a person practicing quackery or a similar confidence trick in order to obtain money, power, fame, or other advantages through pretense or deception. One example of a charlatan appears in the Canterbury Tales story "The Pardoner's Tale," with the Pardoner who tricks sinners into buying fake religious relics. Synonyms for charlatan include shyster, quack, or faker. Quack is a reference to quackery or the practice of dubious medicine, including the sale of snake oil, or a person who does not have medical training who purports to provide medical services.