Motor effects of the partial dopamine agonist (−)‐3‐(3‐hydroxyphenyl)‐N‐n‐propylpiperidine (preclamol) in Parkinson's disease

The motor effects of the partial dopamine agonist (–)‐3‐(3‐hydroxyphenyl)‐N‐n‐propylpiperidine [(–)‐3‐PPP, preclamol] were evaluated in nine patients with Parkinson's disease using a double‐blind, placebocontrolled design. (–)‐3‐PPP monotherapy had an antiparkinsonian effect in five of nine patients at a mean dose of 37 ± 10 mg intramuscularly. The co‐administration of (–)‐3‐PPP and a mildly dyskinetic dose of levodopa, infused intravenously at steady‐state, resulted in complete suppression of dyskinesias and reemergence of parkinsonian signs in two of seven patients. These dopamine antagonist effects of (–)‐3‐PPP occurred at relatively low (2.5 and 5 mg) doses. Our results suggest that partial dopamine agonists can exert agonist or antagonist activity in parkinsonian patients depending on concurrent dopaminergic tone. Although this dual action of (–)‐3‐PPP and other partial agonists could be therapeutically important on theoretical grounds, the small number of patients manifesting a clinically significant response and the frequently inconsistent effects could indicate that this class of agents may have relatively limited clinical utility.