The most common cause of secondary parkinsonism is Use of drugs that decrease dopaminergic activity These drugs include Antipsychotics (eg, phenothiazine, thioxanthene, butyrophenone) Antiemetics and gastrointestinal drugs (eg, metoclopramide, prochlorperazine, cinitapride, clebopride) Drugs that deplete dopamine (eg, tetrabenazine, reserpine) Outside the US, cinnarizine and flunarizine Table Etiology reference 1.