Bromocriptine and dopamine receptor stimulation.

The response to different doses of bromocriptine (12.5, 25, 50 and 100 mg) has been established in six patients with Parkinson's disease. Bromocriptine, like levodopa, causes improved mobility in patients with Parkinsonism, emesis, hallucinations, a fall in supine and erect blood pressure, increase of plasma growth hormone and suppression of prolactin concentration. Bromocriptine (50 or 100 mg) has as great an anti-Parkinsonian effect as average therapeutic doses of levodopa, and a longer duration of action, 6-10 hours. In the dose range studied, bromocriptine appears to be a complete dopamine agonist, although 100 mg was less effective than 50 mg in two patients. The different actions of bromocriptine and other dopamine agonist drugs may result from stimulation of different types of dopamine receptor.