Quinidine is a class IA antiarrhythmic agent used to treat heart rhythm disturbances. It is a stereoisomer of antimalarial agent quinine, originally derived from the bark of the cinchona tree. The drug causes increased action potential duration, as well as a prolonged QT interval. As of 2019 it is no longer being manufactured for use in the United States.
Quinine and Quinidine is sometimes detected as a cutting agent in street drugs such as cocaine and heroin.
June 2022 cfsre Report – Quinine & Quinidine: Toxic Adulterants Found in Illicit Street Drugs