Entacapone

INDICATIONS AND USAGE Entacapone tablets USP are indicated as an adjunct to levodopa and carbidopa to treat end-of-dose "wearing-off" in patients with Parkinson's disease (see CLINICAL PHARMACOLOGY, Clinical Studies ). Entacapone's effectiveness has not been systematically evaluated in patients with Parkinson's disease who do not experience end-of-dose "wearing-off".

DOSAGE AND ADMINISTRATION The recommended dose of entacapone is one 200 mg tablet administered concomitantly with each levodopa and carbidopa dose to a maximum of 8 times daily (200 mg × 8 = 1,600 mg per day). Clinical experience with daily doses above 1,600 mg is limited. Entacapone should always be administered in association with levodopa and carbidopa. Entacapone has no antiparkinsonian effect of its own. In clinical studies, the majority of patients required a decrease in daily levodopa dose if their daily dose of levodopa had been greater than or equal to 800 mg or if patients had moderate or severe dyskinesia before beginning treatment. To optimize an individual patient's response, reductions in daily levodopa dose or extending the interval between doses may be necessary. In clinical studies, the average reduction in daily levodopa dose was about 25% in those patients requiring a levodopa dose reduction. (More than 58% of patients with levodopa doses above 800 mg daily required such a reduction.) Entacapone can be combined with both the immediate and sustained-release formulations of levodopa and carbidopa. Entacapone may be taken with or without food (see CLINICAL PHARMACOLOGY ). Patients With Impaired Hepatic Function Patients with hepatic impairment should be treated with caution. The AUC and C max of entacapone approximately doubled in patients with documented liver disease, compared to controls. However, these studies were conducted with single-dose entacapone without levodopa and dopa decarboxylase inhibitor coadministration, and therefore the effects of liver disease on the kinetics of chronically administered entacapone have not been evaluated (see CLINICAL PHARMACOLOGY, Pharmacokinetics of Entacapone ). Withdrawing Patients from Entacapone Rapid withdrawal or abrupt reduction in the entacapone dose could lead to emergence of signs and symptoms of Parkinson's disease (see CLINICAL PHARMACOLOGY, Clinical Studies ), and may lead to hyperpyrexia and confusion, a symptom complex resembling NMS (see PRECAUTIONS, Other Events Reported With Dopaminergic Therapy ). This syndrome should be considered in the differential diagnosis for any patient who develops a high fever or severe rigidity. If a decision is made to discontinue treatment with entacapone, patients should be monitored closely and other dopaminergic treatments should be adjusted as needed. Although tapering entacapone has not been systematically evaluated, it seems prudent to withdraw patients slowly if the decision to discontinue treatment is made.

ADVERSE REACTIONS Because clinical studies are conducted under widely varying conditions, the incidence of adverse reactions (number of unique patients experiencing an adverse reaction associated with treatment per total number of patients treated) observed in the clinical studies of a drug cannot be directly compared to the incidence of adverse reactions in the clinical studies of another drug and may not reflect the incidence of adverse reactions observed in practice. A total of 1,450 patients with Parkinson's disease were treated with entacapone in premarketing clinical studies. Included were patients with fluctuating symptoms, as well as those with stable responses to levodopa therapy. All patients received concomitant treatment with levodopa preparations, however, and were similar in other clinical aspects. The most commonly observed adverse reactions (incidence at least 3% greater than placebo) in double-blind, placebo-controlled studies (N=1,003) associated with the use of entacapone were: dyskinesia, urine discoloration, diarrhea, nausea, hyperkinesia, abdominal pain, vomiting, and dry mouth. Approximately 14% of the 603 patients given entacapone in the double-blind, placebo-controlled studies discontinued treatment due to adverse reactions, compared to 9% of the 400 patients who received placebo. The most frequent causes of discontinuation in decreasing order were: psychiatric disorders (2% vs. 1%), diarrhea (2% vs. 0%), dyskinesia and hyperkinesia (2% vs. 1%), nausea (2% vs. 1%), and abdominal pain (1% vs. 0%). Adverse Event Incidence in Controlled Clinical Studies Table 4 lists treatment-emergent adverse events that occurred in at least 1% of patients treated with entacapone participating in the double-blind, placebo-controlled studies and that were numerically more common in the entacapone group, compared to placebo. In these studies, either entacapone or placebo was added to levodopa and carbidopa (or levodopa and benserazide). Table 4: Summary of Patients with Adverse Events after Start of Trial Drug Administration At least 1% in Entacapone Group and Greater Than Placebo SYSTEM ORGAN CLASS Entacapone Placebo Preferred term (n = 603) % of patients (n = 400)) % of patients SKIN AND APPENDAGES DISORDERS Sweating increased 2 1 MUSCULOSKELETAL SYSTEM DISORDERS Back pain 2 1 CENTRAL AND PERIPHERAL NERVOUS SYSTEM DISORDERS Dyskinesia 25 15 Hyperkinesia 10 5 Hypokinesia 9 8 Dizziness 8 6 SPECIAL SENSES, OTHER DISORDERS Taste perversion 1 0 PSYCHIATRIC DISORDERS Anxiety 2 1 Somnolence 2 0 Agitation 1 0 GASTROINTESTINAL SYSTEM DISORDERS Nausea 14 8 Diarrhea 10 4 Abdominal pain 8 4 Constipation 6 4 Vomiting 4 1 Mouth dry 3 0 Dyspepsia 2 1 Flatulence 2 0 Gastritis 1 0 Gastrointestinal disorders 1 0 RESPIRATORY SYSTEM DISORDERS Dyspnea 3 1 PLATELET, BLEEDING AND CLOTTING DISORDERS Purpura 2 1 URINARY SYSTEM DISORDERS Urine discoloration 10 0 BODY AS A WHOLE - GENERAL DISORDERS Back pain 4 2 Fatigue 6 4 Asthenia 2 1 RESISTANCE MECHANISM DISORDERS Infection bacterial 1 0 Effects of Gender and Age on Adverse Reactions No differences were noted in the rate of adverse events attributable to entacapone by age or gender. Postmarketing Reports The following spontaneous reports of adverse events temporally associated with entacapone have been identified since market introduction and are not listed in Table 4. Because these reactions are reported voluntarily from a population of unknown size, it is not always possible to reliably estimate their frequency or establish causal relationship to entacapone exposure. Hepatitis with mainly cholestatic features has been reported.

Drug Interactions See PRECAUTIONS, Drug Interactions . Drug Interactions In vitro studies of human CYP enzymes showed that entacapone inhibited the CYP enzymes 1A2, 2A6, 2C9, 2C19, 2D6, 2E1 and 3A only at very high concentrations (IC50 from 200 microM to over 1,000 microM; an oral 200 mg dose achieves a highest level of approximately 5 microM in people); these enzymes would therefore not be expected to be inhibited in clinical use. In an interaction study in healthy volunteers, entacapone did not significantly change the plasma levels of S-warfarin while the AUC for R-warfarin increased on average by 18% [Cl90 11% to 26%], and the INR values increased on average by 13% [Cl90 6% to 19%]. Nevertheless, cases of significantly increased INR in patients concomitantly using warfarin have been reported during the postapproval use of entacapone. Therefore, monitoring of INR is recommended when entacapone treatment is initiated or when the dose is increased for patients receiving warfarin.

Store at 20º to 25ºC (68º to 77ºF); excursions permitted to 15°C to 30°C (59°F to 86°F). [See USP Controlled Room Temperature.]