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Mechanism Of Action
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. The precise mechanism of action of ropinirole as a treatment for Restless Legs Syndrome is unknown, although it is thought to be related to its ability to stimulate dopamine receptors.
Clinical experience with dopamine agonists, including ropinirole, suggests an association with impaired ability to regulate blood pressure with resulting orthostatic hypotension, especially during dose escalation. In some patients in clinical trials, blood pressure changes were associated with the emergence of orthostatic symptoms, bradycardia, and, in one case in a healthy volunteer, transient sinus arrest with syncope [see WARNINGS AND PRECAUTIONS].
The mechanism of orthostatic hypotension induced by ropinirole is presumed to be due to a D2-mediated blunting of the noradrenergic response to standing and subsequent decrease in peripheral vascular resistance. Nausea is a common concomitant symptom of orthostatic signs and symptoms.
At oral doses as low as 0.2 mg, ropinirole suppressed serum prolactin concentrations in healthy male volunteers.
Ropinirole had no dose-related effect on ECG wave form and rhythm in young, healthy, male volunteers in the range of 0.01 to 2.5 mg.
Ropinirole had no dose- or exposure-related effect on mean QT intervals in healthy male and female volunteers titrated to doses up to 4 mg/day. The effect of ropinirole on QTc intervals at higher exposures achieved either due to drug interactions, hepatic impairment, or at higher doses has not been systematically evaluated.
Ropinirole displayed linear kinetics over the dosing range of 1 to 8 mg three times daily. Steady-state concentrations are expected to be achieved within 2 days of dosing. Accumulation upon multiple dosing is predictive from single dosing.
Ropinirole is rapidly absorbed after oral administration, reaching peak concentration in approximately 1 to 2 hours. In clinical trials, 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.
Relative bioavailability from a tablet compared with an oral solution is 85%. Food does not affect the extent of absorption of ropinirole, although its Tmax is increased by 2.5 hours and its Cmax is decreased by approximately 25% when the drug is taken with a high-fat meal.
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.
Ropinirole is extensively metabolized by the liver. The major metabolic pathways are Ndespropylation and hydroxylation to form the inactive N-despropyl metabolite and hydroxyl 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.
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%).
Digoxin: Coadministration of REQUIP (2 mg three 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 three times daily) in 12 patients with Parkinson's disease. REQUIP (2 mg three times daily) did not alter the pharmacokinetics of theophylline (5 mg/kg IV) in 12 patients with Parkinson's disease.
Ciprofloxacin: Coadministration of ciprofloxacin (500 mg twice daily), an inhibitor of CYP1A2, with REQUIP (2 mg three times daily) increased ropinirole AUC by 84% on average and Cmax 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 REQUIP (2 mg three times daily) had no effect on the steady-state pharmacokinetics of ropinirole (n = 28 patients). Oral administration of REQUIP 2 mg three times daily increased mean steadystate Cmax 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, and anticholinergics, did not affect the clearance of ropinirole. An in vitro study indicates that ropinirole is not a substrate for P-gp. 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.
Because therapy with REQUIP 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 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.
Gender: Female and male patients showed similar clearance.
Race: 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 RLS, 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.
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.
A trial of ropinirole in subjects with end-stage renal disease on hemodialysis has shown that clearance of ropinirole was reduced by approximately 30%. The recommended maximum dose should be lower in these patients [see DOSAGE AND ADMINISTRATION].
The use of ropinirole in subjects with severe renal impairment (creatinine clearance less than 30 mL/min) without regular dialysis has not been studied.
Hepatic Impairment: The pharmacokinetics of ropinirole have not been studied in patients with hepatic impairment. Because ropinirole is extensively metabolized by the liver, these patients may have higher plasma levels and lower clearance of ropinirole than patients with normal hepatic function.
Other Diseases: Population pharmacokinetic analysis revealed no change in the clearance of ropinirole in patients with concomitant diseases such as hypertension, depression, osteoporosis/arthritis, and insomnia compared with patients with Parkinson's disease only.
The effectiveness of REQUIP in the treatment of Parkinson's disease was evaluated in a multinational drug development program consisting of 11 randomized, controlled trials. Four trials were conducted in patients with early Parkinson's disease and no concomitant levodopa (L-dopa) and seven trials were conducted in patients with advanced Parkinson's disease with concomitant L-dopa. Three placebo-controlled trials provide evidence of effectiveness of REQUIP in the management of patients with Parkinson's disease who were and were not receiving concomitant L-dopa. Two of these three trials enrolled patients with early Parkinson's disease (without L-dopa) and one enrolled patients receiving L-dopa.
In these trials a variety of measures were used to assess the effects of treatment (e.g., the Unified Parkinson's Disease Rating Scale [UPDRS], Clinical Global Impression [CGI] scores, patient diaries recording time “on” and “off,” tolerability of L-dopa dose reductions).
In both trials of patients with early Parkinson's disease (without L-dopa), the motor component (Part III) of the UPDRS was the primary outcome assessment. The UPDRS is a multi-item rating scale intended to evaluate mentation (Part I), activities of daily living (Part II), motor performance (Part III), and complications of therapy (Part IV). Part III of the UPDRS contains 14 items designed to assess the severity of the cardinal motor findings in patients with Parkinson's disease (e.g., tremor, rigidity, bradykinesia, postural instability) scored for different body regions and has a maximum (worst) score of 108. In the trial of patients with advanced Parkinson's disease (with L-dopa), both reduction in percent awake time spent “off” and the ability to reduce the daily use of L-dopa were assessed as a combined endpoint and individually.
Trials in Patients with Early Parkinson's Disease (without L-dopa)
Trial 1 was a 12-week multicenter trial in which 63 patients with idiopathic Parkinson's disease receiving concomitant anti-Parkinson medication (but not L-dopa) were enrolled and 41 were randomized to REQUIP and 22 to placebo. Patients had a mean disease duration of approximately 2 years. Patients were eligible for enrollment if they presented with bradykinesia and at least tremor, rigidity, or postural instability. In addition, they must have been classified as Hoehn & Yahr Stage I-IV. This scale, ranging from I = unilateral involvement with minimal impairment to V = confined to wheelchair or bed, is a standard instrument used for staging patients with Parkinson's disease. The primary outcome measure in this trial was the proportion of patients experiencing a decrease (compared with baseline) of at least 30% in the UPDRS motor score.
Patients were titrated for up to 10 weeks, starting at 0.5 mg twice daily, with weekly increments of 0.5 mg twice daily to a maximum of 5 mg twice daily. Once patients reached their maximally tolerated dose (or 5 mg twice daily), they were maintained on that dose through 12 weeks. The mean dose achieved by patients at trial endpoint was 7.4 mg/day. Mean baseline UPDRS motor score was 18.6 for patients treated with REQUIP and 19.9 for patients treated with placebo. At the end of 12 weeks, the percentage of responders was greater on REQUIP than on placebo and the difference was statistically significant (Table 6).
Table 6: Percent Responders for UPDRS Motor Score in
Trial 1 (Intent-to-Treat Population)
|% Responders||Difference from Placebo|
Trial 2 in patients with early Parkinson's disease (without L-dopa) was a double-blind, randomized, placebo-controlled, 6-month trial. In this trial, 241 patients were enrolled and 116 were randomized to REQUIP and 125 to placebo. Patients were essentially similar to those in the trial described above; concomitant use of selegiline was allowed, but patients were not permitted to use anticholinergics or amantadine during the trial. Patients had a mean disease duration of 2 years and limited (not more than a 6-week period) or no prior exposure to L-dopa. The starting dosage of REQUIP in this trial was 0.25 mg three times daily. The dosage was titrated at weekly intervals by increments of 0.25 mg three times daily to a dosage of 1 mg three times daily. Further titrations at weekly intervals were at increments of 0.5 mg three times daily up to a dosage of 3 mg three times daily, and then weekly at increments of 1 mg three times daily. Patients were to be titrated to a dosage of at least 1.5 mg three times daily and then to their maximally tolerated dosage, up to a maximum of 8 mg three times daily. The mean dose attained in patients at trial endpoint was 15.7 mg/day.
The primary measure of effectiveness was the mean percent reduction (improvement) from baseline in the UPDRS motor score. At the end of the 6-month trial, patients treated with REQUIP showed improvement in motor score compared with placebo and the difference was statistically significant (Table 7).
Table 7: Mean Percentage Change from Baseline in UPDRS
Motor Score at End of Treatment in Trial 2 (Intent-to-Treat Population)
|Treatment||Baseline UPDRS Motor Score||Mean Change from Baseline||Difference from Placebo|
Trial in Patients with Advanced Parkinson's Disease (with L-dopa)
Trial 3 was a double-blind, randomized, placebo-controlled, 6-month trial that randomized 149 patients (Hoehn & Yahr II-IV) who were not adequately controlled on L-dopa. Ninety-five patients were randomized to REQUIP and 54 were randomized to placebo. Patients in this trial had a mean disease duration of approximately 9 years, had been exposed to L-dopa for approximately 7 years, and had experienced “on-off” periods with L-dopa therapy. Patients previously receiving stable doses of selegiline, amantadine, and/or anticholinergic agents could continue on these agents during the trial. Patients were started at a dosage of 0.25 mg three times daily of REQUIP and titrated upward by weekly intervals until an optimal therapeutic response was achieved. The maximum dosage of trial medication was 8 mg three times daily. All patients had to be titrated to at least a dosage of 2.5 mg three times daily. Patients could then be maintained on this dosage level or higher for the remainder of the trial. Once a dosage of 2.5 mg three times daily was achieved, patients underwent a mandatory reduction in their L-dopa dosage, to be followed by additional mandatory reductions with continued escalation of the dosage of REQUIP. Reductions in the dosage of L-dopa were also allowed if patients experienced adverse reactions that the investigator considered related to dopaminergic therapy. The mean dose attained at trial endpoint was 16.3 mg/day. The primary outcome was the proportion of responders, defined as patients who were able both to achieve a decrease (compared with baseline) of at least 20% in their L-dopa dosage and a decrease of at least 20% in the proportion of the time awake in the “off” condition (a period of time during the day when patients are particularly immobile), as determined by subject diary. In addition, the mean change in “off” time from baseline and the percent change from baseline in daily L-dopa dosage were examined.
At the end of 6 months, the percentage of responders was greater on REQUIP than on placebo and the difference was statistically significant (Table 8).
Based on the protocol-mandated reductions in L-dopa dosage with escalating doses of REQUIP, patients treated with REQUIP had a 19.4% mean reduction in L-dopa dosage while patients treated with placebo had a 3% reduction. Mean daily L-dopa dosage at baseline was 759 mg for patients treated with REQUIP and 843 mg for patients treated with placebo.
The mean number of daily “off” hours at baseline was 6.4 hours for patients treated with REQUIP and 7.3 hours for patients treated with placebo. At the end of the 6-month trial, there was a mean reduction of 1.5 hours of “off” time in patients treated with REQUIP and a mean reduction of 0.9 hours of “off” time in patients treated with placebo, resulting in a treatment difference of 0.6 hours of “off” time.
Table 8: Mean Responder Percentage of Patients
Reducing Daily L-Dopa Dosage by at Least 20% and Daily Proportion of “Off” Time
by at Least 20% at End of Treatment in Trial 3 (Intent-to-Treat Population)
|Treatment||% Responders||Difference from Placebo|
Restless Legs Syndrome
The effectiveness of REQUIP in the treatment of RLS was demonstrated in randomized, doubleblind, placebo-controlled trials in adults diagnosed with RLS using the International Restless Legs Syndrome Study Group diagnostic criteria. Patients were required to have a history of a minimum of 15 RLS episodes/month during the previous month and a total score of ≥ 15 on the International RLS Rating Scale (IRLS scale) at baseline. Patients with RLS secondary to other conditions (e.g., pregnancy, renal failure, anemia) were excluded. All trials employed flexible dosing, with patients initiating therapy at 0.25 mg REQUIP once daily. Patients were titrated based on clinical response and tolerability over 7 weeks to a maximum of 4 mg once daily. All doses were taken between 1 and 3 hours before bedtime.
A variety of measures were used to assess the effects of treatment, including the IRLS scale and Clinical Global Impression-Global Improvement (CGI-I) scores. The IRLS scale contains 10 items designed to assess the severity of sensory and motor symptoms, sleep disturbance, daytime somnolence, and impact on activities of daily living and mood associated with RLS. The range of scores is 0 to 40, with 0 being absence of RLS symptoms and 40 the most severe symptoms. Three of the controlled trials utilized the change from baseline in the IRLS scale at the Week 12 endpoint as the primary efficacy outcome.
Three hundred eighty patients were randomized to receive REQUIP (n = 187) or placebo (n = 193) in a US trial (RLS-1); 284 were randomized to receive either REQUIP (n = 146) or placebo (n = 138) in a multinational trial (excluding US) (RLS-2); and 267 patients were randomized to REQUIP (n = 131) or placebo (n = 136) in a multinational trial (including US) (RLS-3). Across the three trials, the mean duration of RLS was 16 to 22 years (range: 0 to 65 years), mean age was approximately 54 years (range: 18 to 79 years), and approximately 61% were women. The mean dose at Week 12 was approximately 2 mg/day for the three trials.
At baseline, mean total IRLS score was 22.0 for REQUIP and 21.6 for placebo in RLS-1, was 24.4 for REQUIP and 25.2 for placebo in RLS-2, and was 23.6 for REQUIP and 24.8 for placebo in RLS-3. In all three trials, a statistically significant difference between the treatment group receiving REQUIP and the treatment group receiving placebo was observed at Week 12 for both the mean change from baseline in the IRLS scale total score and the percentage of patients rated as responders (much improved or very much improved) on the CGI-I (see Table 9).
Table 9: Mean Change in Total IRLS Score and Percent
Responders on CGI-I
|REQUIP||Placebo||Difference from Placebo|
|Mean change in total IRLS score at Week 12|
|Percent responders on CGI-I at Week 12|
Long-term maintenance of efficacy in the treatment of RLS was demonstrated in a 36-week trial. Following a 24-week, single-blind treatment phase (flexible dosages of REQUIP of 0.25 to 4 mg once daily), patients who were responders (defined as a decrease of > 6 points on the IRLS scale total score relative to baseline) were randomized in double-blind fashion to placebo or continuation of REQUIP for an additional 12 weeks. Relapse was defined as an increase of at least 6 points on the IRLS scale total score to a total score of at least 15, or withdrawal due to lack of efficacy. For patients who were responders at Week 24, the mean dose of REQUIP was 2 mg (range: 0.25 to 4 mg). Patients continued on REQUIP demonstrated a significantly lower relapse rate compared with patients randomized to placebo (32.6% versus 57.8%, P = 0.0156).
Last reviewed on RxList: 1/8/2016
This monograph has been modified to include the generic and brand name in many instances.
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