Absorption: In clinical studies with immediate-release ropinirole, over 88% of a radiolabeled dose was recovered in urine, and the absolute bioavailability was 45% to 55%, indicating approximately 50% first-pass effect.

Ropinirole displayed linear kinetics up to doses of 24 mg/day (8 mg immediate-release, 3 times a day). Increase in systemic exposure of ropinirole following oral administration of 2 to 12 mg of REQUIP XL was approximately dose-proportional. For REQUIP XL, steady-state concentrations of ropinirole are expected to be achieved within 4 days of dosing.

Relative bioavailability of REQUIP XL Extended-Release Tablets compared with immediate-release tablets was approximately 100%. In a repeat-dose study in patients with Parkinson’s disease using REQUIP XL 8 mg, the dose-normalized AUC(0-24) and Cmin for REQUIP XL and immediate-release ropinirole were similar. Dose-normalized Cmax was, on average, 12% lower for REQUIP XL than for the immediate-release formulation and the median time-to-peak concentration was 6 to 10 hours. In a single-dose study, administration of REQUIP XL to healthy volunteers with food (i.e., high-fat meal) increased AUC by approximately 30% and Cmax by approximately 44%, compared with dosing under fasted conditions. In a repeat-dose study in patients with Parkinson’s disease, food (i.e., high-fat meal) increased AUC by approximately 20% and Cmax by approximately 44%; Tmax was prolonged by 3 hours (median prolongation) compared with dosing under fasted conditions [see Dosage and Administration (2.1)].

Distribution: Ropinirole is widely distributed throughout the body, with an apparent volume of distribution of 7.5 L/kg (cv = 32%). It is up to 40% bound to plasma proteins and has a blood-to-plasma ratio of 1:1.

Metabolism: Ropinirole is extensively metabolized by the liver. The major metabolic pathways are N-despropylation and hydroxylation to form the inactive N-despropyl metabolite and hydroxy metabolites. The N-despropyl metabolite is converted to carbamyl glucuronide, carboxylic acid, and N-despropyl hydroxy metabolites. The hydroxy metabolite of ropinirole is rapidly glucuronidated.

In vitro studies indicate that the major cytochrome P450 isozyme involved in the metabolism of ropinirole is CYP1A2, an enzyme known to be induced by smoking and omeprazole, and inhibited by, for example, fluvoxamine, mexiletine, and the older fluoroquinolones such as ciprofloxacin and norfloxacin.

Elimination: The clearance of ropinirole after oral administration to patients is 47 L/hr (cv = 45%) and its elimination half-life is approximately 6 hours. Less than 10% of the administered dose is excreted as unchanged drug in urine. N-despropyl ropinirole is the predominant metabolite found in urine (40%), followed by the carboxylic acid metabolite (10%), and the glucuronide of the hydroxy metabolite (10%).

Drug Interactions:Ciprofloxacin: Coadministration of ciprofloxacin (500 mg twice daily), an inhibitor of CYP1A2, with immediate-release ropinirole (2 mg 3 times daily) increased ropinirole AUC by 84% on average and Cmax by 60% (n = 12 patients).

Digoxin: Coadministration of immediate-release ropinirole (2 mg 3 times daily) with digoxin (0.125 to 0.25 mg once daily) did not alter the steady-state pharmacokinetics of digoxin in 10 patients.

Theophylline: Administration of theophylline (300 mg twice daily, a substrate of CYP1A2) did not alter the steady-state pharmacokinetics of immediate-release ropinirole (2 mg 3 times daily) in 12 patients with Parkinson’s disease. Immediate-release ropinirole (2 mg 3 times daily) did not alter the pharmacokinetics of theophylline (5 mg/kg IV) in 12 patients with Parkinson’s disease.

L-dopa: Coadministration of carbidopa + l-dopa (SINEMET 10/100 mg twice daily) with immediate-release ropinirole (2 mg 3 times daily) had no effect on the steady-state pharmacokinetics of ropinirole (n = 28 patients). Oral administration of immediate-release ropinirole 2 mg 3 times daily increased mean steady-state Cmax of l-dopa by 20%, but its AUC was unaffected (n = 23 patients).

Estrogens: Population pharmacokinetic analysis revealed that higher doses of estrogens (usually associated with hormone replacement therapy [HRT]) reduced the oral clearance of ropinirole by approximately 35%.

Commonly Administered Drugs: Population analysis showed that commonly administered drugs, e.g., selegiline, amantadine, tricyclic antidepressants, benzodiazepines, ibuprofen, thiazides, antihistamines, and anticholinergics, did not affect the oral clearance of ropinirole.

Population Subgroups: Because therapy with REQUIP XL is initiated at a low dose and gradually titrated upward according to clinical tolerability to obtain the optimum therapeutic effect, adjustment of the initial dose based on gender, weight, or age is not necessary.

Age: Oral clearance of ropinirole is reduced by approximately 15% in patients above 65 years of age compared with younger patients. Dosage adjustment is not necessary in the elderly (above 65 years), as the dose of ropinirole is individually titrated to clinical response.

Gender: Female and male patients showed similar oral clearance.

Race: The influence of race on the pharmacokinetics of ropinirole has not been evaluated.

Renal Impairment: Based on population pharmacokinetic analysis, no difference was observed in the pharmacokinetics of ropinirole in patients with moderate renal impairment (creatinine clearance between 30 to 50 mL/min) compared with an age-matched population with creatinine clearance above 50 mL/min. Therefore, no dosage adjustment is necessary in patients with moderate renal impairment. The use of ropinirole in patients with severe renal impairment has not been studied.

The effect of hemodialysis on ropinirole clearance is not known, but because of the relatively high apparent volume of distribution of ropinirole (7.5 L/kg), significant removal of ropinirole by hemodialysis is unlikely.

Hepatic Impairment: The pharmacokinetics of ropinirole have not been studied in patients with hepatic impairment. These patients may have higher plasma levels and lower clearance of ropinirole than patients with normal hepatic function. REQUIP XL should be titrated with caution in this population.

Other Diseases: Population pharmacokinetic analysis revealed no change in the oral clearance of ropinirole in patients with concomitant diseases such as hypertension, depression, osteoporosis/arthritis, and insomnia compared with patients who had Parkinson’s disease only.