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, 5.11)].

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.

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 tablets, median dose 3.0 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 tablets, 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 tablets, 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 tablets 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 tablets.

A total of 1056 patients with Parkinson's disease who participated in two pramipexole dihydrochloride extended-release tablets 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 tablets, 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 tablets or after starting or increasing the dose of pramipexole dihydrochloride extended-release tablets. 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 delirium.

Patients with a major psychotic disorder should ordinarily not be treated with dopamine agonists, including pramipexole dihydrochloride extended-release tablets, because of the risk of exacerbating the psychosis. In addition, certain medications used to treat psychosis may exacerbate the symptoms of Parkinson's disease and may decrease the effectiveness of pramipexole dihydrochloride extended-release tablets [see Drug Interactions (7.1)].

5.5 Dyskinesia

Pramipexole dihydrochloride extended-release tablets may cause or exacerbate preexisting dyskinesia.

5.6 Postural Deformity

Postural deformities, including antecollis, camptocormia (Bent Spine Syndrome), and pleurothotonus (Pisa Syndrome), have been reported in patients after starting or increasing the dose of pramipexole dihydrochloride extended-release tablets. Postural deformity may occur several months after starting treatment or increasing the dose. Reducing the dose or discontinuing pramipexole dihydrochloride extended-release tablets has been reported to improve postural deformity in some patients, and should be considered if postural deformity occurs.

5.7 Renal Impairment

The elimination of pramipexole is dependent on renal function [see Clinical Pharmacology (12.3)]. Patients with mild renal impairment (a creatinine clearance above 50 mL/min) require no reduction in daily dose. Pramipexole dihydrochloride extended-release tablets have not been studied in patients with moderate to severe renal impairment (creatinine clearance <50 mL/min) or on hemodialysis [see Dosage and Administration (2.2), Use in Specific Populations (8.6), and Clinical Pharmacology (12.3)].

5.8 Rhabdomyolysis

In the clinical development program for immediate-release pramipexole tablets, a single case of rhabdomyolysis occurred in a 49-year-old male with advanced Parkinson's disease. The patient was hospitalized with an elevated CPK (10,631 IU/L). The symptoms resolved with discontinuation of the medication.

Advise patients to contact a physician if they experience any unexplained muscle pain, tenderness, or weakness, as these may be symptoms of rhabdomyolysis.

5.9 Retinal Pathology

Human Data

A two-year open-label, randomized, parallel-group safety study of retinal deterioration and vision compared immediate-release pramipexole tablets and immediate-release ropinirole. Two hundred thirty four Parkinson's disease patients (115 on pramipexole, mean dose 3.0 mg/day and 119 on ropinirole, mean dose 9.5 mg/day) were evaluated using a panel of clinical ophthalmological assessments. Of 234 patients who were evaluable, 196 had been treated for two years and 29 were judged to have developed clinical abnormalities that were considered meaningful (19 patients in each treatment arm had received treatment for less than two years). There was no statistical difference in retinal deterioration between the treatment arms; however, the study was only capable of detecting a very large difference between treatments. In addition, because the study did not include an untreated comparison group (placebo treated), it is unknown whether the findings reported in patients treated with either drug are greater than the background rate in an aging population.

Animal Data

Pathologic changes (degeneration and loss of photoreceptor cells) were observed in the retina of albino rats in a 2-year carcinogenicity study. While retinal degeneration was not diagnosed in pigmented rats treated for 2 years, a thinning in the outer nuclear layer of the retina was slightly greater in rats given drug compared with controls. Evaluation of the retinas of albino mice, monkeys, and minipigs did not reveal similar changes. The potential significance of this effect for humans has not been established, but cannot be disregarded because disruption of a mechanism that is universally present in vertebrates (i.e., disk shedding) may be involved [see Nonclinical Toxicology (13.2)].

5.10 Events Reported with Dopaminergic Therapy

Although the events enumerated below may not have been reported with the use of pramipexole in its development program, they are associated with the use of other dopaminergic drugs. The expected incidence of these events, however, is so low that even if pramipexole caused these events at rates similar to those attributable to other dopaminergic therapies, it would be unlikely that even a single case would have occurred in a cohort of the size exposed to pramipexole in studies to date.

Hyperpyrexia and Confusion

Although not reported with pramipexole in the clinical development program, a symptom complex resembling the neuroleptic malignant syndrome (characterized by elevated temperature, muscular rigidity, altered consciousness, and autonomic instability), with no other obvious etiology, has been reported in association with rapid dose reduction, withdrawal of, or changes in dopaminergic therapy. If possible, avoid sudden discontinuation or rapid dose reduction in patients taking pramipexole dihydrochloride extended-release tablets. If the decision is made to discontinue pramipexole dihydrochloride extended-release tablets, the dose should be tapered to reduce the risk of hyperpyrexia and confusion [see Dosage and Administration (2.2)].

Fibrotic Complications

Cases of retroperitoneal fibrosis, pulmonary infiltrates, pleural effusion, pleural thickening, pericarditis, and cardiac valvulopathy have been reported in patients treated with ergot-derived dopaminergic agents. While these complications may resolve when the drug is discontinued, complete resolution does not always occur.

Although these adverse events are believed to be related to the ergoline structure of these compounds, whether other, non-ergot derived dopamine agonists can cause them is unknown.

Cases of possible fibrotic complications, including peritoneal fibrosis, pleural fibrosis, and pulmonary fibrosis have been reported in the postmarketing experience with immediate-release pramipexole tablets. While the evidence is not sufficient to establish a causal relationship between pramipexole and these fibrotic complications, a contribution of pramipexole cannot be completely ruled out.

5.11 Withdrawal Symptoms

Symptoms including apathy, anxiety, depression, fatigue, insomnia, sweating, and pain have been reported during taper or after discontinuation of dopamine agonists, including pramipexole dihydrochloride extended-release tablets. These symptoms generally do not respond to levodopa.

Prior to discontinuation of pramipexole dihydrochloride extended-release tablets, patients should be informed about potential withdrawal symptoms, and monitored during and after discontinuation. In case of severe withdrawal symptoms, a trial re-administration of a dopamine agonist at the lowest effective dose may be considered.

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 pramipexole dihydrochloride extended-release 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 dihydrochloride 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 tablets 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 Tablets in Early Parkinson's Disease

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 tablets -treated patients during the titration phase and persisted (≥7 days) into the maintenance phase (i.e., pramipexole dihydrochloride extended-release tablets % - 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 pramipexole dihydrochloride extended-release 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 pramipexole dihydrochloride extended-release 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 tablets 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 Tablets in Advanced Parkinson's Disease

Because this flexible dose study used a 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 tablets -treated patients during the titration phase and persisted (≥7 days) into the maintenance phase (i.e., pramipexole dihydrochloride extended-release tablets % - placebo % = treatment difference ≥2%); persistent adverse reactions were dyskinesia and insomnia.

Laboratory Tests

During the development of pramipexole dihydrochloride extended-release tablets, no systematic abnormalities on routine laboratory testing were noted.

Other adverse reactions observed during clinical trials of pramipexole dihydrochloride immediate-release tablets or pramipexole dihydrochloride extended-release tablets in early and advanced Parkinson's disease.

Other adverse reactions in clinical studies involving pramipexole dihydrochloride immediate-release tablets or pramipexole dihydrochloride extended-release tablets include abnormal dreams, akathisia, amnesia, decreased libido, decreased weight, dyspnea, pneumonia, and vision abnormalities.

6.2 Postmarketing Experience

The following adverse reactions have been identified during post-approval use of pramipexole dihydrochloride immediate-release tablets or pramipexole dihydrochloride extended-release tablets, primarily in Parkinson's disease patients. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Decisions to include these reactions in labeling are typically based on one or more of the following factors: (1) seriousness of the reaction, (2) frequency of reporting, or (3) strength of causal connection to pramipexole tablets.

Cardiac Disorders: cardiac failure

Gastrointestinal Disorders: vomiting

General Disorders and Administration Site Conditions: withdrawal symptoms [see Warnings and Precautions (5.11)]

Metabolism and Nutrition Disorders: syndrome of inappropriate antidiuretic hormone secretion (SIADH), weight increase

Musculoskeletal and Connective Tissue Disorders: postural deformity [see Warnings and Precautions (5.6)]

Nervous System Disorders: syncope

Skin and Subcutaneous Tissue Disorders: skin reactions (including erythema, rash, pruritus, urticaria)

There are postmarketing reports of patients noticing tablet residue in their stool that resembles a swollen pramipexole dihydrochloride extended-release tablets whole tablet or swollen pieces of the tablet. Some patients have reported worsening of their Parkinson's disease symptoms when tablet residue was observed. If a patient reports tablet residue with worsening of their Parkinson's symptoms, prescribers may need to re-evaluate their medications.

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.

8.1 Pregnancy

Risk Summary

There are no adequate data on the developmental risk associated with the use of pramipexole dihydrochloride extended-release tablets in pregnant women. No adverse developmental effects were observed in animal studies in which pramipexole was administered to rabbits during pregnancy. Effects on embryofetal development could not be adequately assessed in pregnant rats; however, postnatal growth was inhibited at clinically relevant exposures [see Data].

In the U.S. general population, the estimated background risk of major birth defects and of miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively. The background risk of major birth defects and miscarriage for the indicated population is unknown.

Data

Animal Data

Oral administration of pramipexole (0.1, 0.5, or 1.5 mg/kg/day) to pregnant rats during the period of organogenesis resulted in a high incidence of total resorption of embryos at the highest dose tested. This increase in embryolethality is thought to result from the prolactin-lowering effect of pramipexole; prolactin is necessary for implantation and maintenance of early pregnancy in rats but not in rabbits or humans. Because of pregnancy disruption and early embryonic loss in this study, the teratogenic potential of pramipexole could not be adequately assessed in rats. The highest no-effect dose for embryolethality in rats was associated with maternal plasma drug exposures (AUC) approximately equal to those in humans receiving the maximum recommended human dose (MRHD) of 4.5 mg/day. There were no adverse effects on embryo-fetal development following oral administration of pramipexole (0.1, 1, or 10 mg/kg/day) to pregnant rabbits during organogenesis (plasma AUC up to approximately 70 times that in humans at the MRHD). Postnatal growth was inhibited in the offspring of rats treated with pramipexole (0.1, 0.5, or 1.5 mg/kg/day) during the latter part of pregnancy and throughout lactation. The no-effect dose for adverse effects on offspring growth (0.1 mg/kg/day) was associated with maternal plasma drug exposures lower than that in humans at the MRHD.

8.2 Lactation

Risk Summary

There are no data on the presence of pramipexole in human milk, the effects of pramipexole on the breastfed infant, or the effects of pramipexole on milk production. However, inhibition of lactation is expected because pramipexole inhibits secretion of prolactin in humans. Pramipexole or metabolites, or both, are present in rat milk [see Data].

The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for pramipexole dihydrochloride extended-release tablets and any potential adverse effects on the breastfed infant from pramipexole dihydrochloride extended-release tablets or from the underlying maternal condition.

Data

In a study of radio-labeled pramipexole, pramipexole or metabolites, or both, were present in rat milk at concentrations three to six times higher than those in maternal plasma.

8.4 Pediatric Use

Safety and effectiveness of pramipexole dihydrochloride extended-release tablets in pediatric patients have not been evaluated.

8.5 Geriatric Use

Pramipexole total oral clearance is approximately 30% lower in subjects older than 65 years compared with younger subjects, because of a decline in pramipexole renal clearance due to an age-related reduction in renal function. This resulted in an increase in elimination half-life from approximately 8.5 hours to 12 hours. In a placebo-controlled clinical trial of pramipexole dihydrochloride extended-release tablets in early Parkinson's disease, 47% of the 259 patients were ≥65 years of age. Among patients receiving pramipexole dihydrochloride extended-release tablets, hallucinations were more common in the elderly, occurring in 13% of the patients ≥65 years of age compared to 2% of the patients <65 years of age.

8.6 Renal Impairment

The elimination of pramipexole is dependent upon renal function. Pramipexole clearance is extremely low in dialysis patients, as a negligible amount of pramipexole is removed by dialysis [see Dosage and Administration (2.2), Warnings and Precautions (5.7), and Clinical Pharmacology (12.3)].

12.1 Mechanism of Action

Pramipexole is a non-ergot dopamine agonist with high relative in vitro specificity and full intrinsic activity at the D2 subfamily of dopamine receptors, binding with higher affinity to D3 than to D2 or D4 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 D3 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 (Cmax, Cmin) 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 Cmax 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 Cmax by approximately 20% and delayed Tmax 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 Cmax by about 40% and a decrease in Tmax 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: Cimetidine, a known inhibitor of renal tubular secretion of organic bases via the cationic transport system, caused a 50% increase in pramipexole AUC and a 40% increase in half-life (N=12).

Probenecid: Probenecid, a known inhibitor of renal tubular secretion of organic acids via the anionic transporter, did not noticeably influence pramipexole pharmacokinetics (N=12).

Other drugs eliminated via renal secretion: Population pharmacokinetic analysis suggests that co-administration of drugs that are secreted by the cationic transport system (e.g., cimetidine, ranitidine, diltiazem, triamterene, verapamil, quinidine, and quinine) decreases the oral clearance of pramipexole by about 20%, while those secreted by the anionic transport system (e.g., cephalosporins, penicillins, indomethacin, hydrochlorothiazide, and chlorpropamide) are likely to have little effect on the oral clearance of pramipexole. Other known organic cation transport substrates and/or inhibitors (e.g., cisplatin and procainamide) may also decrease the clearance of pramipexole.

CYP interactions: Inhibitors of cytochrome P450 enzymes would not be expected to affect pramipexole elimination because pramipexole is not appreciably metabolized by these enzymes in vivo or in vitro. Pramipexole does not inhibit CYP enzymes CYP1A2, CYP2C9, CYP2C19, CYP2E1, and CYP3A4. Inhibition of CYP2D6 was observed with an apparent Ki of 30 µM, indicating that pramipexole will not inhibit CYP enzymes at plasma concentrations observed following the clinical dose of 4.5 mg/day.

Drugs affecting gastrointestinal motility or gastric pH: Population pharmacokinetic analysis suggests that co-administration of antacids (N=6) decreased the oral clearance of pramipexole by about 25%, while H2-blockers (N=5), anticholinergics (N=27), propulsive (N=7), and proton pump inhibitors (N=16) are likely to have little effect on the oral clearance of pramipexole.

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Two-year carcinogenicity studies with pramipexole have been conducted in mice and rats. Pramipexole was administered in the diet to mice at doses up to 10 mg/kg/day [or approximately 10 times the maximum recommended human dose (MRHD) of 1.5 mg TID on a mg/m2 basis]. Pramipexole was administered in the diet to rats at doses up to 8 mg/kg/day. These doses were associated with plasma AUCs up to approximately 12 times that in humans at the MRHD. No significant increases in tumors occurred in either species.

Pramipexole was not mutagenic or clastogenic in a battery of in vitro (bacterial reverse mutation, V79/HGPRT gene mutation, chromosomal aberration in CHO cells) and in vivo (mouse micronucleus) assays.

In rat fertility studies, pramipexole at a dose of 2.5 mg/kg/day (5 times the MRHD on a mg/m2 basis) prolonged estrus cycles and inhibited implantation. These effects were associated with reductions in serum levels of prolactin, a hormone necessary for implantation and maintenance of early pregnancy in rats.

13.2 Animal Toxicology and/or Pharmacology

Retinal Pathology in Albino Rats

Pathologic changes (degeneration and loss of photoreceptor cells) were observed in the retina of albino rats in the 2-year carcinogenicity study with pramipexole. These findings were first observed during week 76 and were dose-dependent in animals receiving 2 or 8 mg/kg/day (plasma AUCs equal to 2.5 and 12.5 times that in humans at the MRHD of 1.5 mg TID). In a similar study of pigmented rats with 2-years exposure to pramipexole at 2 or 8 mg/kg/day, retinal degeneration was not observed. Animals given drug had thinning in the outer nuclear layer of the retina that was only slightly greater than that seen in control rats.

Investigative studies demonstrated that pramipexole reduced the rate of disk shedding from the photoreceptor rod cells of the retina in albino rats, which was associated with enhanced sensitivity to the damaging effects of light. In a comparative study, degeneration and loss of photoreceptor cells occurred in albino rats after 13 weeks of treatment with 25 mg/kg/day of pramipexole (54 times the highest clinical dose on a mg/m2 basis) and constant light (100 lux), but not in pigmented rats exposed to the same dose and higher light intensities (500 lux). Thus, the retina of albino rats is considered to be uniquely sensitive to the damaging effects of pramipexole and light. Similar changes in the retina did not occur in a 2-year carcinogenicity study in albino mice treated with 0.3, 2, or 10 mg/kg/day (0.3, 2.2, and 11 times the highest clinical dose on a mg/m2 basis). Evaluation of the retinas of monkeys given 0.1, 0.5, or 2.0 mg/kg/day of pramipexole (0.4, 2.2, and 8.6 times the highest clinical dose on a mg/m2 basis) for 12 months and minipigs given 0.3, 1, or 5 mg/kg/day of pramipexole for 13 weeks also detected no changes.

The potential significance of this effect in humans has not been established, but cannot be disregarded because disruption of a mechanism that is universally present in vertebrates (i.e., disk shedding) may be involved.

Fibro-osseous Proliferative Lesions in Mice

An increased incidence of fibro-osseous proliferative lesions occurred in the femurs of female mice treated for 2 years with 0.3, 2.0, or 10 mg/kg/day (0.3, 2.2, and 11 times the highest clinical dose on a mg/m2 basis). Lesions occurred at a lower rate in control animals. Similar lesions were not observed in male mice or rats and monkeys of either sex that were treated chronically with pramipexole. The significance of this lesion to humans is not known.

16.1 How Supplied

Pramipexole dihydrochloride extended-release tablets are available as follows:

0.375 mg: white to off-white, round, convex shaped, extended-release tablets debossed with "002" on one side and plain on the other side.

Unit of Use Bottles of 30  NDC 69680-145-30

0.75 mg: white to off-white, round, convex shaped, extended-release tablets debossed with "003" on one side and plain on the other side.

Unit of Use Bottles of 30  NDC 69680-146-30

16.2 Storage and Handling

Store at 20°C to 25°C (68°F to 77°F); excursions permitted to 15°C to 30°C (59°F to 86°F) [see USP Controlled Room Temperature]. Protect from exposure to high humidity. Store in a safe place out of the reach of children.