Drugs can be classified in several ways, including by their effects on the body, therapeutic uses, and chemical characteristics. Classifying drugs into groups helps identify similarities and differences. Prescription drugs require a doctor's approval while over-the-counter drugs do not. Drugs are also classified by regulatory agencies based on their abuse and addiction potential, with Schedule I having the highest risk and Schedule V the lowest. Pregnancy categories further classify drugs based on their safety for use during pregnancy.

1. P. David Falkenstein, PA-C, MS, DFAAPA