antiparkinsonian /-pär″kənsōnē·ən/ , pertaining to a substance or procedure used to treat parkinsonism. Drugs for this neurological disorder are of two kinds: those that compensate for the lack of dopamine in the corpus striatum and anticholinergic agents that counteract the activity of the abundant acetylcholine in the corpus striatum. Synthetic levodopa, a dopamine precursor that crosses the blood-brain barrier, reduces the rigidity, sluggishness, dysphagia, drooling, and instability characteristic of the disease but does not alter its relentless course. Centrally active cholinergic blockers, notably benztropine mesylate, biperiden hydrochloride, procyclidine hydrochloride, and trihexyphenidyl hydrochloride, may relieve tremors and rigidity and improve mobility. The antiviral agent amantadine hydrochloride is often effective in the treatment of parkinsonism; its mechanism of action is not established, but it apparently increases release of dopamine in the brain. Therapeutic approaches to the relief of the symptoms of parkinsonism include alcohol injection, cautery, cryosurgery, and surgical excision performed to destroy the globus pallidus (reducing rigidity) and parts of the thalamus (reducing tremor). Extrapyramidal symptoms similar to those of idiopathic parkinsonism are frequently induced by antipsychotic drugs.
