Ropinirole, a non-ergoline dopamine agonist, has selective affinity for dopamine D2-like receptors and little or no affinity for non-dopaminergic brain receptors. Ropinirole is indicated as adjunct therapy to levodopa in patients with advanced Parkinson's disease. It is also indicated, and recent clinical trials have focused on its use, as monotherapy in patients with early Parkinson's disease. In the symptomatic treatment of early Parkinson's disease ropinirole monotherapy was significantly more effective than placebo in 2 multicentre, randomised, double-blind trials of 3 to 12 months duration as assessed by the Unified Parkinson's Disease Rating Scale (UPDRS) motor scores and Clinical Global Impression/Clinical Global Evaluation Scales. In a similarly designed 3-year comparative study with bromocriptine, ropinirole recipients showed a significant improvement in UPDRS- activities of daily living (ADL) scores; however, motor scores were similar between the 2 groups. Ropinirole and levodopa treatments were similar in efficacy as measured by UPDRS ADL scores, although ropinirole recipients showed significantly less improvement on UPDRS motor scores at the 5-year study end-point in a multicentre, randomised double-blind trial. As an adjunct therapy to levodopa in patients with more advanced Parkinson's disease, ropinirole was reported to be as effective as bromocriptine and significantly more effective than placebo. In general in the comparisons with placebo ropinirole allowed a > or =20% reduction in the concomitant dose of levodopa without compromising efficacy in a significant proportion of patients and, in some trials decreased the amount of awake time spent in the 'off' state ('off' state is defined as a gradual return to parkinsonism despite adequate medication). Ropinirole was well tolerated either as monotherapy or as an adjunct to levodopa treatment. Nausea, dizziness and somnolence were the most commonly reported adverse events and were reported at a higher incidence by patients receiving ropinirole than by those receiving placebo. In patients with early Parkinson's disease, ropinirole generally showed a similar overall tolerability profile to bromocriptine although, over a 3-year period nausea was more commonly reported with ropinirole recipients. In a 5-year study, the incidence of dyskinesia was significantly lower with ropinirole than with levodopa regardless of levodopa supplementation. Prior to the addition of supplementary levodopa 5% of ropinirole recipients had experienced dyskinesia compared with 36% of those receiving levodopa.
In patients with early Parkinson's disease, ropinirole monotherapy was more efficacious than bromocriptine with regard to improvement in activities of daily living, and need for supplemental levodopa. Ropinirole recipients had a higher requirement for levodopa supplementation than levodopa recipients in a 5-year study, but the incidence of dyskinesia was significantly lower with ropinirole than with levodopa (markedly so in the one third of ropinirole recipients who were able to remain on monotherapy with no levodopa supplementation). Thus available data suggest that ropinirole may provide a means of treating early Parkinson's disease while minimising the risk of dyskinesia and delaying the need for supplemental levodopa in some patients. In addition, ropinirole is also efficacious in the management of more advanced Parkinson's disease in patients who are experiencing motor complications after long term levodopa use.