Ropiniroleinteractions

Inhibitors or inducers of CYP1A2: May alter the clearance of ropinirole; dose adjustment of ropinirole may be required.

Hormone replacement therapy (HRT): Starting or stopping HRT may require dose adjustment of ropinirole.

Dopamine antagonists (e.g., neuroleptics, metoclopramide): May reduce efficacy of ropinirole.

7.1 Cytochrome P450 1A2

Inhibitors and Inducers In vitro metabolism studies showed that cytochrome P450 1A2 (CYP1A2) is the major enzyme responsible for the metabolism of ropinirole. There is thus the potential for inducers or inhibitors of this enzyme to alter the clearance of ropinirole. Therefore, if therapy with a drug known to be a potent inducer or inhibitor of CYP1A2 is stopped or started during treatment with ropinirole, adjustment of the dose of ropinirole may be required. Coadministration of ciprofloxacin, an inhibitor of CYP1A2, increases the AUC and C max of ropinirole. Cigarette smoking is expected to increase the clearance of ropinirole since CYP1A2 is known to be induced by smoking hormone replacement therapy.

7.2 Estrogens

Population pharmacokinetic analysis revealed that higher doses of estrogens (usually associated with hormone replacement therapy) reduced the clearance of ropinirole. Starting or stopping may require adjustment of dosage of ropinirole.

7.3 Dopamine

Antagonists Because ropinirole is a dopamine agonist, it is possible that dopamine antagonists such as neuroleptics (e.g., phenothiazines, butyrophenones, thioxanthenes) or metoclopramide may reduce the efficacy of ropinirole.

Drug Interaction Studies Digoxin: Coadministration of 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 ropinirole (2 mg 3 times daily) in 12 patients with Parkinson’s disease. Ropinirole (2 mg 3 times daily) did not alter the pharmacokinetics of theophylline (5 mg/kg intravenously) in 12 patients with Parkinson’s disease.

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

Estrogens: Population pharmacokinetic analysis revealed that estrogens (mainly ethinylestradiol: intake 0.6 to 3 mg over 4-month to 23-year period) reduced the oral clearance of ropinirole by 36% in 16 patients.

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

Commonly Administered Drugs: Population analysis showed that commonly administered drugs (e.g., selegiline, amantadine, tricyclic antidepressants, benzodiazepines, ibuprofen, thiazides, antihistamines, anticholinergics) did not affect the clearance of ropinirole. An in vitro study indicates that ropinirole is not a substrate for P-glycoprotein. Ropinirole and its circulating metabolites do not inhibit or induce P450 enzymes; therefore, ropinirole is unlikely to affect the pharmacokinetics of other drugs by a P450 mechanism.