chlordiazepoxide, tranquilizing drug used in the treatment of anxiety. The drug was introduced in the 1960s under several trade names, including Libritabs (the original base) and Librium (the hydrochloride salt). Chlordiazepoxide belongs to a group of chemically related compounds called benzodiazepines. Administered orally or by injection, it can be used as a sedative to relieve anxiety either before or after surgery, to control anxiety associated with acute alcohol withdrawal, and to treat panic disorders. Among the most common side effects are drowsiness, confusion, and an inability to control voluntary muscular movements. Prolonged use may lead to physical dependence.