Pramipexole

INDICATIONS AND USAGE Pramipexole dihydrochloride tablets are a non-ergot dopamine agonist indicated for the treatment of: • Parkinson’s disease (PD) ( 1.1 ) • Moderate-to-severe primary Restless Legs Syndrome (RLS) ( 1.2 ) 1.1 Parkinson's Disease Pramipexole dihydrochloride tablets are indicated for the treatment of Parkinson's disease. 1.2 Restless Legs Syndrome Pramipexole dihydrochloride tablets are indicated for the treatment of moderate-to-severe primary Restless Legs Syndrome (RLS).

DOSAGE AND ADMINISTRATION Pramipexole dihydrochloride extended-release tablets are taken once daily, with or without food ( 2.1 ) Tablets must be swallowed whole and must not be chewed, crushed, or divided ( 2.1 ) Starting dose is 0.375 mg given once daily ( 2.2 ) Dose may be increased gradually, not more frequently than every 5 to 7 days, first to 0.75 mg per day and then by 0.75 mg increments up to a maximum recommended dose of 4.5 mg per day. Assess therapeutic response andtolerability at a minimal interval of 5 days or longer after each dose increment ( 2.2 ) Patients may be switched overnight from immediate-release pramipexole tablets to pramipexole dihydrochloride extended-release tablets at the same daily dose. Dose adjustment may be needed in some patients ( 2.3 ) Pramipexole dihydrochloride extended-release tablets should be discontinued gradually ( 2.2 ) 2.1 General Dosing Considerations Pramipexole dihydrochloride extended-release tablets are taken orally once daily, with or without food. Pramipexole dihydrochloride extended-release tablets must be swallowed whole and must not be chewed, crushed, or divided. If a significant interruption in therapy with pramipexole dihydrochloride extended-release tablets has occurred, re-titration of therapy may be warranted. 2.2 Dosing for Parkinson’s Disease The starting dose is 0.375 mg given once per day. Based on efficacy and tolerability, dosages may be increased gradually, not more frequently than every 5 to 7 days, first to 0.75 mg per day and then by 0.75 mg increments up to a maximum recommended dose of 4.5 mg per day. In clinical trials, dosage was initiated at 0.375 mg/day and gradually titrated based on individual therapeutic response and tolerability. Doses greater than 4.5 mg/day have not been studied in clinical trials. Patients should be assessed for therapeutic response and tolerability at a minimal interval of 5 days or longer after each dose increment [ see Clinical Studies ( 14 ) ]. Due to the flexible dose design used in clinical trials, specific dose-response information could not be determined [ see Clinical Studies ( 14 ) ]. Pramipexole dihydrochloride extended-release tablets may be tapered off at a rate of 0.75 mg per day until the daily dose has been reduced to 0.75 mg. Thereafter, the dose may be reduced by 0.375 mg per day [ see Warnings and Precautions ( 5.10 ) ]. Dosing in Patients with Renal Impairment In patients with moderate renal impairment (creatinine clearance between 30 and 50 mL/min), pramipexole dihydrochloride extended-release tablets should initially be taken every other day. Caution should be exercised and careful assessment of therapeutic response and tolerability should be made before increasing to daily dosing after one week, and before any additional titration in 0.375 mg increments up to 2.25 mg per day. Dose adjustment should occur no more frequently than at weekly intervals. Pramipexole dihydrochloride extended-release tablets have not been studied in patients with severe renal impairment (creatinine clearance <30 mL/min) or patients on hemodialysis, and are not recommended in these patients. 2.3 Switching from Immediate-Release Pramipexole Tablets to Pramipexole Dihydrochloride Extended-Release Tablets Patients with Parkinson’s disease may be switched overnight from immediate-release pramipexole tablets to pramipexole dihydrochloride extended-release tablets at the same daily dose. When switching between immediate-release pramipexole tablets and pramipexole dihydrochloride extended-release tablets, patients should be monitored to determine if dosage adjustment is necessary. 2.1 General Dosing Considerations Pramipexole dihydrochloride extended-release tablets are taken orally once daily, with or without food. Pramipexole dihydrochloride extended-release tablets must be swallowed whole and must not be chewed, crushed, or divided. If a significant interruption in therapy with pramipexole dihydrochloride extended-release tablets has occurred, re-titration of therapy may be warranted. 2.2 Dosing for Parkinson’s Disease The starting dose is 0.375 mg given once per day. Based on efficacy and tolerability, dosages may be increased gradually, not more frequently than every 5 to 7 days, first to 0.75 mg per day and then by 0.75 mg increments up to a maximum recommended dose of 4.5 mg per day. In clinical trials, dosage was initiated at 0.375 mg/day and gradually titrated based on individual therapeutic response and tolerability. Doses greater than 4.5 mg/day have not been studied in clinical trials. Patients should be assessed for therapeutic response and tolerability at a minimal interval of 5 days or longer after each dose increment [ see Clinical Studies ( 14 ) ]. Due to the flexible dose design used in clinical trials, specific dose-response information could not be determined [ see Clinical Studies ( 14 ) ]. Pramipexole dihydrochloride extended-release tablets may be tapered off at a rate of 0.75 mg per day until the daily dose has been reduced to 0.75 mg. Thereafter, the dose may be reduced by 0.375 mg per day [ see Warnings and Precautions ( 5.10 ) ]. Dosing in Patients with Renal Impairment In patients with moderate renal impairment (creatinine clearance between 30 and 50 mL/min), pramipexole dihydrochloride extended-release tablets should initially be taken every other day. Caution should be exercised and careful assessment of therapeutic response and tolerability should be made before increasing to daily dosing after one week, and before any additional titration in 0.375 mg increments up to 2.25 mg per day. Dose adjustment should occur no more frequently than at weekly intervals. Pramipexole dihydrochloride extended-release tablets have not been studied in patients with severe renal impairment (creatinine clearance <30 mL/min) or patients on hemodialysis, and are not recommended in these patients. 2.3 Switching from Immediate-Release Pramipexole Tablets to Pramipexole Dihydrochloride Extended-Release Tablets Patients with Parkinson’s disease may be switched overnight from immediate-release pramipexole tablets to pramipexole dihydrochloride extended-release tablets at the same daily dose. When switching between immediate-release pramipexole tablets and pramipexole dihydrochloride extended-release tablets, patients should be monitored to determine if dosage adjustment is necessary.

WARNINGS AND PRECAUTIONS Falling Asleep During Activities of Daily Living: Sudden onset of sleep may occur without warning; advise patients to report symptoms. (5.1) Symptomatic Orthostatic Hypotension: Monitor closely especially during dose escalation. (5.2) Impulse Control/Compulsive Behaviors: Patients may experience compulsive behaviors and other intense urges. (5.3) Hallucinations and Psychotic-like Behavior: May occur; risk increases with age. (5.4) Dyskinesia: May be caused or exacerbated by pramipexole dihydrochloride extended-release. (5.5) Postural Deformity: Consider reducing the dose or discontinuing pramipexole dihydrochloride extended-release tablets if postural deformity occurs. ( 5.6 ) 5.1 Falling Asleep During Activities of Daily Living and Somnolence Patients treated with pramipexole have reported falling asleep while engaged in activities of daily living, including the operation of motor vehicles, which sometimes resulted in accidents. Although many of these patients reported somnolence while on pramipexole tablets, some perceived that they had no warning signs (sleep attack) such as excessive drowsiness, and believed that they were alert immediately prior to the event. Some of these events had been reported as late as one year after the initiation of treatment. In placebo-controlled clinical trials in Parkinson's disease, the sudden onset of sleep or sleep attacks were reported in 8 of 387 (2%) patients treated with pramipexole dihydrochloride extended-release tablets compared to 2 of 281 (1%) patients on placebo. In early Parkinson’s disease, somnolence was reported in 36% of 223 patients treated with pramipexole dihydrochloride extended-release, median dose 3 mg/day, compared to 15% of 103 patients on placebo. In advanced Parkinson’s disease, somnolence was reported in 15% of 164 patients treated with pramipexole dihydrochloride extended-release tablets, median dose 3 mg/day, compared to 16% of 178 patients on placebo. It has been reported that falling asleep while engaged in activities of daily living usually occurs in a setting of preexisting somnolence, although patients may not give such a history. For this reason, prescribers should reassess patients for drowsiness or sleepiness, especially since some of the events occur well after the start of treatment. Prescribers should also be aware that patients may not acknowledge drowsiness or sleepiness until directly questioned about drowsiness or sleepiness during specific activities. Before initiating treatment with pramipexole dihydrochloride extended-release tablets, advise patients of the potential to develop drowsiness, and specifically ask about factors that may increase the risk for somnolence such as the use of concomitant sedating medications or alcohol, the presence of sleep disorders, and concomitant medications that increase pramipexole plasma levels (e.g., cimetidine) [see Clinical Pharmacology (12.3) ]. If a patient develops significant daytime sleepiness or episodes of falling asleep during activities that require active participation (e.g., conversations, eating, etc.), pramipexole dihydrochloride extended-release tablets should ordinarily be discontinued. If a decision is made to continue pramipexole dihydrochloride extended-release tablets, advise patients not to drive and to avoid other potentially dangerous activities that might result in harm if the patients become somnolent. While dose reduction reduces the degree of somnolence, there is insufficient information to establish that dose reduction will eliminate episodes of falling asleep while engaged in activities of daily living. 5.2 Symptomatic Orthostatic Hypotension Dopamine agonists, in clinical studies and clinical experience, appear to impair the systemic regulation of blood pressure, with resulting orthostatic hypotension, especially during dose escalation. Parkinson's disease patients, in addition, appear to have an impaired capacity to respond to an orthostatic challenge. For these reasons, Parkinson's disease patients being treated with dopaminergic agonists, including pramipexole dihydrochloride extended-release, ordinarily require careful monitoring for signs and symptoms of orthostatic hypotension, especially during dose escalation, and should be informed of this risk. In placebo-controlled clinical trials in Parkinson’s disease, symptomatic orthostatic hypotension was reported in 10 of 387 (3%) patients treated with pramipexole dihydrochloride extended-release tablets compared to 3 of 281 (1%) patients on placebo. One patient of 387 on pramipexole dihydrochloride extended-release tablets discontinued treatment due to hypotension. 5.3 Impulse Control/Compulsive Behaviors Case reports and the results of cross-sectional studies suggest that patients can experience intense urges to gamble, increased sexual urges, intense urges to spend money, binge eating, and/or other intense urges, and the inability to control these urges while taking one or more of the medications, including pramipexole dihydrochloride extended-release, that increase central dopaminergic tone. In some cases, although not all, these urges were reported to have stopped when the dose was reduced or the medication was discontinued. Because patients may not recognize these behaviors as abnormal, it is important for prescribers to specifically ask patients or their caregivers about the development of new or increased gambling urges, sexual urges, uncontrolled spending or other urges while being treated with pramipexole dihydrochloride extended-release for Parkinson’s disease. Physicians should consider dose reduction or stopping the medication if a patient develops such urges while taking pramipexole dihydrochloride extended-release. A total of 1056 patients with Parkinson’s disease who participated in two pramipexole dihydrochloride extended-release placebo-controlled studies of up to 33 weeks duration were specifically asked at each visit about the occurrence of these symptoms. A total of 14 of 387 (4%) treated with pramipexole dihydrochloride extended-release tablets, 12 of 388 (3%) treated with immediate-release pramipexole tablets, and 4 of 281 (1%) treated with placebo reported compulsive behaviors, including pathological gambling, hypersexuality, and/or compulsive buying. 5.4 Hallucinations and Psychotic-like Behavior In placebo-controlled clinical trials in Parkinson's disease, hallucinations (visual or auditory or mixed) were reported in 25 of 387 (6%) patients treated with pramipexole dihydrochloride extended-release tablets compared to 5 of 281 (2%) patients receiving placebo. Hallucinations led to discontinuation of treatment in 5 of 387 (1%) patients on pramipexole dihydrochloride extended-release tablets. Age appears to increase the risk of hallucinations attributable to pramipexole. In placebo-controlled clinical trials in Parkinson’s disease, hallucinations were reported in 15 of 162 (9%)patients ≥ 65 years of age taking pramipexole dihydrochloride extended-release tablets compared to 10 of 225 (4%)patients <65 years of age taking pramipexole dihydrochloride extended-release tablets. Postmarketing reports with dopamine agonists, including pramipexole dihydrochloride extended-release, indicate that patients with Parkinson’s disease may experience new or worsening mental status and behavioral changes, which may be severe, including psychotic-like behavior during treatment with pramipexole dihydrochloride extended-release or after starting or increasing the dose of pramipexole dihydrochloride extended-release. Other drugs prescribed to improve the symptoms of Parkinson’s disease can have similar effects on thinking and behavior. This abnormal thinking and behavior can consist of one or more of a variety of manifestations including paranoid ideation, delusions, hallucinations, confusion, psychotic-like behavior, symptoms of mania (e.g., insomnia, psychomotor agitation), disorientation, aggressive behavior, agitation, and

CONTRAINDICATIONS None. None ( 4 )

DRUG INTERACTIONS Dopamine antagonists: May diminish the effectiveness of pramipexole ( 7.1 ) 7.1 Dopamine Antagonists Since pramipexole is a dopamine agonist, it is possible that dopamine antagonists, such as the neuroleptics (phenothiazines, butyrophenones, thioxanthenes) or metoclopramide, may diminish the effectiveness of pramipexole dihydrochloride extended-release tablets. 7.1 Dopamine Antagonists Since pramipexole is a dopamine agonist, it is possible that dopamine antagonists, such as the neuroleptics (phenothiazines, butyrophenones, thioxanthenes) or metoclopramide, may diminish the effectiveness of pramipexole dihydrochloride extended-release tablets.

ADVERSE REACTIONS The following adverse reactions are discussed in greater detail in other sections of the labeling: Falling Asleep During Activities of Daily Living and Somnolence [see Warnings and Precautions (5.1) ] Symptomatic Orthostatic Hypotension [see Warnings and Precautions (5.2) ] Impulse Control / Compulsive Behaviors [see Warnings and Precautions (5.3) ] Hallucinations and Psychotic-like Behavior [see Warnings and Precautions (5.4) ] Dyskinesia [see Warnings and Precautions (5.5) ] Postural Deformity [see Warnings and Precautions ( 5.6 ) ] Rhabdomyolysis [see Warnings and Precautions (5.8) ] Retinal Pathology [see Warnings and Precautions (5.9) ] Events Reported with Dopaminergic Therapy [see Warnings and Precautions (5.10) ] Withdrawal Symptoms [see Warnings and Precautions ( 5.11 )] Most common adverse reactions (incidence ≥5% and greater than placebo) : Early PD without levodopa: somnolence, nausea, constipation, dizziness, fatigue, hallucinations, dry mouth, muscle spasms, and peripheral edema (6.1) Advanced PD with levodopa: dyskinesia, nausea, constipation, hallucinations, headache, and anorexia (6.1) To report SUSPECTED ADVERSE REACTIONS, contact Dr. Reddy’s Laboratories, Inc. at 1-888-375-3784 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug (or of another development program of a different formulation of the same drug) and may not reflect the rates observed in practice. During the premarketing development of pramipexole dihydrochloride extended-release tablets, patients with early Parkinson's disease were treated with pramipexole dihydrochloride extended-release tablets, placebo, or immediate-release pramipexole tablets. In addition, a randomized, double-blind, parallel group trial was conducted in 156 early Parkinson’s disease patients (Hoehn & Yahr Stages I-III) to assess overnight switching of immediate-release pramipexole tablets to extended-release pramipexole tablets. In this latter study, concomitant treatment with stable doses of levodopa, monoamine oxidase B inhibitor (MAOB-I) drugs, anticholinergics, or amantadine, individually or in combination, was allowed. In a third trial, advanced Parkinson’s disease patients received pramipexole extended-release tablets, placebo, or immediate-release pramipexole tablets as adjunctive therapy to levodopa. Early Parkinson's Disease The most common adverse reactions (≥5% and more frequent than placebo) after 33 weeks of treatment with pramipexole dihydrochloride extended-release tablets in the trial of early Parkinson’s disease patients were somnolence, nausea, constipation, dizziness, fatigue, hallucinations, dry mouth, muscle spasms, and peripheral edema. Twenty four of 223 (11%) patients treated with pramipexole dihydrochloride extended-release tablets for 33 weeks discontinued treatment due to adverse reactions compared to 4 of 103 (4%) patients who received placebo and approximately 20 of 213 (9%) patients who received immediate-release pramipexole tablets. The adverse reaction most commonly causing discontinuation of treatment with pramipexole dihydrochloride extended-release tablets was nausea (2%). Table 1 lists adverse reactions that occurred with a frequency of at least 2% with pramipexole dihydrochloride extended-release and were more frequent than with placebo during 33 weeks of treatment in a double-blind, placebo-controlled study in early Parkinson's disease. In this study, patients did not receive concomitant levodopa; however, levodopa was permitted as rescue medication. Table 1 Adverse-Reactions in a 33-Week Double-Blind, Placebo-Controlled Trial with Pramipexole Dihydrochloride Extended-Release in Early Parkinson’s Disease Body System / Adverse Reaction Placebo Extended-Release Pramipexole Immediate Release Pramipexole (n=103) (n=223) (n=213) % % % Nervous system disorders Somnolence 15 36 33 Dizziness 7 12 12 Tremor 1 3 3 Balance disorder 1 2 0 Gastrointestinal disorders Nausea 9 22 24 Constipation 2 14 12 Dry mouth 1 5 4 Vomiting 0 4 4 Upper abdominal pain 1 3 4 Dyspepsia 2 3 3 Abdominal discomfort 0 2 1 Psychiatric disorders Hallucinations, including visual, auditory and mixed 1 5 6 Insomnia 3 4 4 Sleep attacks or sudden onset of sleep 1 3 6 Sleep disorder 1 2 3 Depression 0 2 0 General disorders and administration site conditions Fatigue 4 6 6 Peripheral edema 4 5 8 Asthenia 2 3 1 Musculoskeletal and connective tissue disorders Muscle spasms 3 5 3 Injury, poisoning and procedural complications Fall 1 4 4 Ear and labyrinth disorders Vertigo 1 4 2 Respiratory, thoracic and mediastinal disorders Cough 1 3 3 Metabolism and nutrition disorders Increased appetite 1 3 2 Vascular disorders Orthostatic hypotension 1 3 0 Because this study used a flexible dose titration design, it was not possible to assess the effects of dose on the incidence of adverse reactions. Adverse reactions can initially occur in either the titration or maintenance phase. Some adverse reactions developed in pramipexole dihydrochloride extended-release-treated patients during the titration phase and persisted (≥7 days) into the maintenance phase (i.e., pramipexole dihydrochloride extended-release % - placebo % = treatment difference ≥2%); persistent adverse reactions were somnolence, nausea, constipation, fatigue, and dry mouth. A double-blind, randomized, parallel group trial evaluated the tolerability of an overnight switch from immediate-release pramipexole tablets to extended-release pramipexole tablets at the same daily dose in 156 early Parkinson’s disease patients with or without levodopa. One of 104 patients switched from immediate-release pramipexole tablets to extended-release pramipexole tablets discontinued due to adverse reactions (vertigo and nausea). Advanced Parkinson's Disease The most common adverse reactions (≥5% and greater frequency than in placebo) during 18 weeks of treatment with pramipexole dihydrochloride extended-release tablets in the trial of advanced Parkinson’s disease patients with concomitant levodopa were dyskinesia, nausea, constipation, hallucinations, headache, and anorexia. Eight of 164 (5%) patients treated with pramipexole dihydrochloride extended-release tablets for 18 weeks discontinued treatment due to adverse reactions compared to 7 of 178 (4%) patients who received placebo and 8 of 175 (5%) patients who received immediate-release pramipexole tablets. The most common adverse reactions leading to discontinuation of treatment with pramipexole dihydrochloride extended-release tablets were nausea (1%) and hallucination (1%). Table 2 lists adverse reactions that occurred with a frequency of at least 2% with pramipexole dihydrochloride extended-release and were more frequent than with placebo during 18 weeks of treatment in patients with advanced Parkinson’s disease treated with pramipexole dihydrochloride extended-release tablets. In this study, pramipexole dihydrochloride extended-release tablets, immediate-release pramipexole tablets, or placebo was administered to patients who were also receiving concomitant levodopa. Table 2 Adverse-Reactions in an 18-Week Double-Blind, Placebo-Controlled Trial with Pramipexole Dihydrochloride Extended-Release in Advanced Parkinson’s Disease Body System/Adverse Reaction Placebo Extended-Release Pramipexole Immediate-Release Pramipexole n = 178 n = 164 n = 175 % % % Nervous system disorders Dyskinesia 8 17 18 Headache 3 7 4 Dizziness (postural) 1 2 3 Gastrointestinal disorders Nausea 10 11 11 Constipation 5 7 6 Salivary hypersecretion 0 2 0 Diarrhea 1 2 1 Psychiatric disorders Hallucinations, including visual, auditory and mixed 2 9 7 Insomnia 2 4 4 Metabolism and nutrition disorders Anorexia 2 5 1 Musculoskeletal and connective tissue disorders Back pain 1 2 3 Because this flexib

CLINICAL PHARMACOLOGY 12.1 Mechanism of Action Pramipexole is a non-ergot dopamine agonist with high relative in vitro specificity and full intrinsic activity at the D 2 subfamily of dopamine receptors, binding with higher affinity to D 3 than to D 2 or D 4 receptor subtypes. The precise mechanism of action of pramipexole as a treatment for Parkinson’s disease is unknown, although it is believed to be related to its ability to stimulate dopamine receptors in the striatum. This conclusion is supported by electrophysiologic studies in animals that have demonstrated that pramipexole influences striatal neuronal firing rates via activation of dopamine receptors in the striatum and the substantia nigra, the site of neurons that send projections to the striatum. The relevance of D 3 receptor binding in Parkinson’s disease is unknown. 12.2 Pharmacodynamics The effect of pramipexole on the QT interval of the ECG was investigated in a clinical study in 60 healthy male and female volunteers. All subjects initiated treatment with 0.375 mg pramipexole dihydrochloride extended-release tablets administered once daily, and were up-titrated every 3 days to 2.25 mg and 4.5 mg daily, a faster rate of titration than recommended in the label. No dose- or exposure-related effect on mean QT intervals was observed; however, the study did not have a valid assessment of assay sensitivity. The effect of pramipexole on QTc intervals at higher exposures achieved either due to drug interactions (e.g., with cimetidine), renal impairment, or at higher doses has not been systematically evaluated. Although mean values remained within normal reference ranges throughout the study, supine systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse rate for subjects treated with pramipexole generally increased during the rapid up-titration phase, by 10 mmHg, 7 mmHg, and 10 bpm higher than placebo, respectively. Higher SBP, DBP, and pulse rates compared to placebo were maintained until the pramipexole doses were tapered; values on the last day of tapering were generally similar to baseline values. Such effects have not been observed in clinical studies with Parkinson’s disease patients, who were titrated according to labeled recommendations. 12.3 Pharmacokinetics Pramipexole dihydrochloride extended-release tablets, like immediate-release pramipexole tablets, display linear pharmacokinetics over the entire clinical dosage range. Slow release of pramipexole from pramipexole dihydrochloride extended-release tablets with once-daily administration results in the same daily maximum and minimum pramipexole plasma concentrations (C max , C min ) as three times daily administration of immediate-release pramipexole tablets. Absorption The absolute bioavailability of pramipexole is greater than 90%, indicating that it is well absorbed and undergoes little presystemic metabolism. Increase in systemic exposure of pramipexole following oral administration of 0.375 mg to 4.5 mg of pramipexole dihydrochloride extended-release tablets was dose-proportional. For pramipexole dihydrochloride extended-release tablets, steady state of exposure is reached within 5 days of continuous dosing. Relative bioavailability of pramipexole dihydrochloride extended-release tablets compared with immediate-release tablets was approximately 100%. In a repeat-dose study in healthy, normal volunteers, pramipexole dihydrochloride extended-release tablets 4.5 mg administered once daily was bioequivalent with regard to C max and AUC over 24 hours to immediate-release pramipexole tablets 1.5 mg administered three times daily. The average time-to-peak concentration for pramipexole dihydrochloride extended-release tablets is 6 hours. Administration of pramipexole dihydrochloride extended-release tablets with food (i.e., high-fat meal) did not affect AUC but increased C max by approximately 20% and delayed T max by approximately 2 hours compared with dosing under fasted conditions; these differences are not considered to be clinically relevant [ see Dosage and Administration ( 2.1 ) ]. Distribution Pramipexole is extensively distributed, having a volume of distribution of about 500 L (coefficient of variation [CV] = 20%). It is about 15% bound to plasma proteins. Pramipexole distributes into red blood cells as indicated by an erythrocyte-to-plasma ratio of approximately 2. Metabolism Pramipexole is metabolized only to a negligible extent (<10%). No specific active metabolite has been identified in human plasma or urine. Elimination Urinary excretion is the major route of pramipexole elimination, with 90% of a pramipexole dose recovered in urine, almost all as unchanged drug. The renal clearance of pramipexole is approximately 400 mL/min (CV=25%), approximately three times higher than the glomerular filtration rate. Thus, pramipexole is secreted by the renal tubules, probably by the organic cation transport system. Pharmacokinetics in Specific Populations Because therapy with pramipexole dihydrochloride 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, race, or age is not necessary. However, renal insufficiency causes a large decrease in the ability to eliminate pramipexole. This will necessitate dosage adjustment in patients with moderate to severe renal impairment [ see Dosage and Administration ( 2.2 ) ]. Gender Pramipexole clearance is about 30% lower in women than in men, but this difference can be accounted for by differences in body weight. There is no difference in plasma half-life between males and females. Age Pramipexole clearance is reduced by approximately 30% in the elderly (aged 65 years or older) compared with young, healthy volunteers (aged less than 40 years). This difference is most likely due to the reduction in renal function with age, since pramipexole clearance is correlated with renal function, as measured by creatinine clearance. Race No racial differences in metabolism and elimination have been identified. Hepatic Impairment The influence of hepatic insufficiency on pramipexole pharmacokinetics has not been evaluated. Because approximately 90% of the recovered dose is excreted in the urine as unchanged drug, hepatic impairment would not be expected to have a significant effect on pramipexole elimination. Renal Impairment Clearance of immediate-release pramipexole was about 75% lower in patients with severe renal impairment (creatinine clearance approximately 20 mL/min) and about 60% lower in patients with moderate impairment (creatinine clearance approximately 40 mL/min) compared with healthy volunteers [see Dosage and Administration ( 2.2 ) and Warnings and Precautions ( 5.7 )]. In patients with varying degrees of renal impairment, pramipexole clearance correlates well with creatinine clearance. Therefore, creatinine clearance can be used as a predictor of the extent of decrease in pramipexole clearance. Drug Interactions No specific pharmacokinetic drug interaction trials were conducted with pramipexole dihydrochloride extended-release tablets since the potential for drug interactions mainly depends on the active drug substance pramipexole and not the formulation. The following interaction data were obtained using immediate-release pramipexole tablets. Carbidopa/levodopa: Carbidopa/levodopa did not influence the pharmacokinetics of pramipexole in healthy volunteers (N=10). Pramipexole did not alter the extent of absorption (AUC) or the elimination of carbidopa/levodopa, although it caused an increase in levodopa C max by about 40% and a decrease in T max from 2.5 to 0.5 hours. Selegiline: In healthy volunteers (N=11), selegiline did not influence the pharmacokinetics of pramipexole. Amantadine: Population pharmacokinetic analyses suggest that amantadine may slightly decrease the oral clearance of pramipexole. Cimetidine: Cimetid