Pentylenetetrazol, also known as pentylenetetrazole, metrazol,pentetrazol (INN), pentamethylenetetrazol, Corazol, Cardiazol orPTZ, is a drug formerly used as a circulatory and respiratorystimulant. High doses cause convulsions, as discovered by theHungarian-American neurologist and psychiatrist Ladislas J. Medunain 1934. It has been used in convulsive therapy, and was found tobe effective—primarily for depression—but side-effects such asuncontrolled seizures were difficult to avoid. In 1939pentylenetetrazol was replaced by electroconvulsive therapy, easierto administer, as the preferred method for inducing seizures inEngland's mental hospitals. In the US its approval by the FDA wasrevoked in 1982. It is used in Italy as a coughsuppressant.