Ropinirole Implants Reverse MPTP-Induced Parkinsonism in Rhesus Monkeys

Purpose: We compared efficacy and side effects of ropinirole implants with oral ropinirole in parkinsonian monkeys. Methods: Twenty monkeys received injections of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-hydrochloride (MPTP) to render them parkinsonian. Monkeys were then placed into 3 groups based upon clinical rating scores (CRS). Group 1 received oral ropinirole and placebo implants. Group 2 receivedropinirole implants that released 1/9th of the animals’ optimal daily oral dose and oral placebo. Group 3 received placebo implants and oral placebo. Monkeys were assessed for pharmacokinetic data, CRS, Global Dyskinesia Rating Scale, and skin irritation. Results: For the ropinirole implant group, the activity pattern was similar to that seen pre-MPTP; which extended through the weekends and was greater than control treated parkinsonian monkeys. Oral ropinirole yielded a high degree of variability for activity, with values following oral dosing being higher than the pre-MPTP periodbut levels similar to placebo treated parkinsonian animals during weekends, which were excluded from oral dosing. Implants and oral treatment achieved significant improvement in CRS between 11 60 days and 4 60 days respectively. Conclusion: Low dose ropinirole implants have the potential to provide continuous clinical improvement in bradykinesia with fewer “off periods” and lower risk for medicationinduced psychosis than oral medication.