Ropinirole (SK and F 101468) in the treatment of Parkinson's disease

Ropinirole in the treatment of Parkinson's disease

In this review, the pharmacokinetics, safety and tolerability, and clinical efficacy of ropinirole (Requip), a non-ergoline dopamine agonist approved for use in the treatment of Parkinson's disease (PD) are examined. A summary of preclinical and clinical studies is presented. Ropinirole is safe and efficacious as monotherapy in the treatment of early PD and as an adjunct to levodopa in more advanced cases.

Effects of ropinirole on motor behavior in MPTP-treated common marmosets

The effects of ropinirole (4-[2-(dipropylamino)ethyl]-2-indolinone monohydrochloride), a nonergoline dopamine receptor agonist with a high affinity for native dopamine D(2)-like receptors, on Parkinsonism induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 2.5 mg/animal in common marmosets were examined and compared to the effects of bromocriptine. Ropinirole (0.1-3 mg/kg, PO) increased motor activity dose dependently and reversed akinesia or uncoordinated movement in MPTP-treated marmosets. The activities for ropinirole were very similar to those of bromocriptine. Ropinirole had, however, several properties that differed from those of bromocriptine. Ropinirole caused a more rapid onset of anti-Parkinsonian activity compared to bromocriptine, and had a potency more than five times greater than that of bromocriptine in the improvement of motor deficits. The combination of ropinirole and L-DOPA increased the effectiveness of ropinirole or L-DOPA alone, and produced a more marked additive effect on motor activity than did bromocriptine and L-DOPA. Chronic administration of ropinirole for 21 days produced a statistically significant increase in motor activity compared to the initial administration, and akinesia scores, measured through rating the quality of movements, were also improved without obvious dyskinesia. This study suggests that ropinirole is a dopamine D(2)-like receptor agonistic drug of potential use in the treatment of Parkinson's disease.

Comparative pharmacological study of ropinirole (SKF-101468) and its metabolites in rats

The dopamine receptor agonist ropinirole (SKF-101468) is used to treat Parkinson's disease. Ropinirole is metabolized by two routes to a series of different metabolites although the predominant pathway is species-dependent. It is unknown whether any of the metabolites contribute to its antiparkinsonian activity and whether D3 or D2 receptor agonist activity plays a preferential role. Therefore ropinirole and its primary metabolites, SKF-104557, SKF-97930 and SKF-96990, and the rat metabolite, SKF-89124 were tested in the 6-hydroxydopamine lesion model of Parkinson's disease. SKF-89124 and SKF-96990 were also assayed in radioligand binding and microphysiometer functional assays at cloned human dopamine D2 and D3. Ropinirole and SKF-89124 were equipotent in-vivo, and produced dose-related increases in circling at 0.05-0.8 mg kg(-1), s.c. (ropinirole) and 0.05-0.75 mg kg(-1), s.c. (SKF-89124). Neither SKF-96990 or SKF-97930, at doses up to 15 mg kg(-1), increased the circling rate. Some circling was observed with 15 mg kg(-1) SKF-104557 but the response was less than half that produced by ropinirole (0.8 mgkg(-1)). SKF-104557 was 150-fold less potent than ropinirole. SKF-89124 possessed-30-fold higher affinity for D3 over D2 receptors in radioligand binding studies, but was not selective in the functional microphysiometer assay. SKF-96990 was 10-fold selective for D3 over D2 receptors in the radioligand binding assay. Ropinirole and SKF-104557 are 20-fold selective for D3 over D2 receptors in radioligand binding assays whereas in microphysiometry, selectivity is 10-fold. SKF-97930 is inactive in radioligand binding and microphysiometer assays. Primary metabolites of ropinirole did not contribute significantly to its activity in this model of Parkinson's disease. The lack of dopamine D3/D2 receptor selectivity for ropinirole rules out the possibility of attributing the degree of either D2 or D3 receptor activity to the behavioural efficacy of ropinirole.

Effect of food on the pharmacokinetics of ropinirole in parkinsonian patients

AIMS

Ropinirole is a specific non-ergoline dopamine D2-receptor agonist with antiparkinsonian properties. The pharmacokinetic parameters of ropinirole taken in the fasted condition were compared with those when it was co-administered with food.

METHODS

This was an open, randomized, two sessions cross over study in 12 patients with Parkinson's disease, comparing the steady-state pharmacokinetic profiles of ropinirole on two different study days: 'fasted' and 'fed'.

RESULTS

The mean Cmax was lower in the 'fed' regimen than in the 'fasted' one (-25%, P=0.002). The median tmax was observed 2.6 h later in the 'fed' regimen than in the 'fasted' regimen (P<0.05). There was a slight but significant decrease in AUC(0,8 h) in the 'fed' regimen (P=0.03).

CONCLUSIONS

Food decreases the rate of absorption of ropinirole, but has little effect on the extent of absorption.