Methysergide-induced psychosis: case report with long-term follow-up.

Methysergide, a congener of LSD and potent serotonin (5-HT) antagonist, induced a florid transient psychosis resembling an LSD psychosis in a patient with spasmodic torticollis with a family history of schizophrenia. Thirteen years later he developed a major depression. A variety of other drug challenges and treatments for his torticollis had no psychotomimetic effect. Blockade of 5-HT receptors may subserve methysergide-induced psychosis.