Patent medicines originated in 16th century England. These medicines were ready-made remedies and could be purchased to treat many conditions. Originally, the term referred to medicines that actually were patented. To receive a patent, however, the maker had to reveal all ingredients that went into the medicine. Inventors were often reluctant to reveal a formula and would just register the name of the medicine. In this way they could keep their ingredients secret while retaining exclusive use of a name. In time, all ready-made medicines whether they were patented or not became known as patent medicines.

The term patent medicine has a negative meaning today because of the amount of quackery tied to patent medicines in the 18th, 19th, and early 20th centuries. Some patent medicines actually did contain effective substances and worked as promised. Quinine, digitalis, ipecac, and other substances have genuine medical uses, and...