SummaryBromocriptine, a drug acting directly upon dopaminergic receptors, has been found to have a significant therapeutic action in a double-blind study of 20 patients with idiopathic Parkinsonism whE were already receiving conventional therapy, including levodopa. Neurological deficits improved by almost 20% in severely disabled patients; amelioration of mildly affected patients was about 10%. Adverse reactions were similar to those encountered with levodopa-they were all dose-dependent and reversible. These observations are discussed in relation to certain theoretical advantages which might be expected from a drug which acts directly on dopaminergic receptors.

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In a double-blind trial with a placebo phase, low-dose bromocriptine therapy (average dose, 15 mg per day) produced a significant improvement in 25 idiopathic parkinsonian patients. Tremor and bradykinesia were equally and significantly improved in both the levodopa-treated and the de novo patients. Rigidity was most improved in the levodopa-treated subjects. Age was not a factor in determining the dose of bromocriptine or the degree of improvement. Adverse effects occurred in 30% but were mild and dose-dependent. Four subjects, unable to tolerate initial doses of bromocriptine, withdrew from the trial. A low initial dose (1 mg per day) and slow escalation in dosage produced an optimal, though delayed improvement. Low-dose bromocriptine therapy is effective, does not induce significant dyskinesia nor on-off phenomenon, and is probably an alternative to levodopa as a drug of first choice in Parkinson disease.

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Bromocriptine is a dopamine agonist that induces postural hypotension and can be used as an antihypertensive. The drug inhibits release of norepinephrine (NE) from an isolated artery by stimulating presynaptic receptors. In normotensive subjects it lowers both plasma and cerebrospinal fluid (CSF) levels of NE by 50% and lowers blood pressure moderately in standing subjects and slightly in recumbent subjects. Through central and peripheral mechanisms, bromocriptine inhibits sympathetic nervous discharge of NE.

Drug interactions between levodopa, tranylcypromine, and carbidopa have been studied in 4 patients with idiopathic parkinsonism. Pressor responses were induced by a combination of levodopa and tranylcypromine. These hypertensive reactions were inhibited by carbidopa, indicating that they are mediated at the periphery. Very small doses of levodopa induced an improvement in parkinsonism when patients were concomitantly taking carbidopa and tranylcypromine, but adverse reactions were prominent.