Effect of a cholinomimetic drug (RS 86) in tardive dyskinesia and drug-related parkinsonism.

RS 86, a specific muscarinic agonist, was evaluated in a blind, placebo-controlled, single-dose trial in 10 psychiatric patients with stable tardive dyskinesia (TD). RS 86, 0.5-4 mg orally, produced no significant effects in TD, although 4 mg caused a minimal aggravation in parkinsonism. Side effects of the highest dose (4 mg) included hypersalivation (eight patients), nausea (6), sweating (3), and vomiting (3). It is concluded that treatment with RS 86 and probably other cholinomimetics has no or only limited beneficial effect in TD.