Ropinirole 1 mg (ER) · Tablets

Ropinirole is a non-ergoline dopamine agonist. The precise mechanism of action of ropinirole as a treatment for Parkinson’s disease is unknown, although it is thought to be related to its ability to stimulate dopamine D2 receptors within the caudate-putamen in the brain.

Increase in systemic exposure of ropinirole following oral administration of 2 to 12 mg of ropinirole extended-release tablets was approximately dose-proportional. For ropinirole extended-release tablets, steady-state concentrations of ropinirole are expected to be achieved within 4 days of dosing.

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

The bioavailability of ropinirole extended-release tablets is similar to that of immediate-release ropinirole tablets. In a repeat-dose trial in subjects with Parkinson’s disease using ropinirole extended-release tablets 8 mg, the dose-normalized AUC(0-24) and Cmin for ropinirole extended-release tablets and immediate-release ropinirole were similar. Dose-normalized Cmax was, on average, 12% lower for ropinirole extended-release tablets than for the immediate-release formulation and the median time-to-peak concentration was 6 to 10 hours. In a single-dose trial, administration of ropinirole extended-release tablets 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 trial 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)].

Distribution — Ropinirole is widely distributed throughout the body, with an apparent volume of distribution of 7.5 L/kg. 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 enzyme 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 is 47 L/h 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%).

Specific Populations — Because therapy with ropinirole extended-release tablets 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.

Geriatric Patients: Oral clearance of ropinirole is reduced by 15% in patients older than 65 years compared with younger patients. Dosage adjustment is not necessary in the elderly (older than 65 years), as the dose of ropinirole is to be individually titrated to clinical response.

Male and Female Patients: Male and female patients showed similar clearance.

Racial or Ethnic Groups: The influence of race on the pharmacokinetics of ropinirole has not been evaluated.

Cigarette Smoking: Smoking is expected to increase the clearance of ropinirole since CYP1A2 is known to be induced by smoking. In a trial in patients with Restless Legs Syndrome, smokers (n =7) had an approximately 30% lower Cmax and a 38% lower AUC than did nonsmokers (n = 11) when those parameters were normalized for dose.

Patients with Renal Impairment: Based on population pharmacokinetic analysis, no difference was observed in the pharmacokinetics of ropinirole in subjects 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.