drugs that reduce the severity of early symptoms of Parkinson's disease. Symptoms include tremors, movement and gait abnormalities, and muscle rigidity. Antiparkinsonian agents are generally used in mental health settings in order to counteract drug-induced parkinsonian symptoms, that are common side effects inherent in the use of conventional antipsychotics. Some of these include histamine antagonists (e.g., diphenhydramine), anticholinergic drugs (e.g., bi nztropine, trihexyphenidyl), dopamine-receptor agonists (e.g., carbidopa, levodopa), and other specific enzyme inhibitors.