Patients who had been on antiparkinson medication concomitant with antipsychotic medication for over three months were abruptly withdrawn from the antiparkinson medication. As expected from some prior work, fewer than 10% had a reoccurrence of symptoms requiring the restarting of the antiparkinson medications.
Orlov P, Kasparian G, DiMascio A, Cole JO. Withdrawal of Antiparkinson Drugs. Arch Gen Psychiatry. 1971;25(5):410-412. doi:10.1001/archpsyc.1971.01750170026005