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Comtan

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Comtan

Comtan

SIDE EFFECTS

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 Comtan in pre-marketing 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 Comtan 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 reasons (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 Comtan group, compared to placebo. In these studies, either Comtan 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 Comtan Group and Greater Than Placebo

SYSTEM ORGAN CLASS Preferred term Comtan
(n = 603)
% of patients
Placebo
(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 Comtan have been identified since market introduction and are not listed in Table 4 above. 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 Comtan exposure.

Hepatitis with mainly cholestatic features has been reported.

Drug Abuse And Dependence

Comtan is not a controlled substance. Animal studies to evaluate the drug abuse and potential dependence have not been conducted. Although clinical studies have not revealed any evidence of the potential for abuse, tolerance or physical dependence, systematic studies in humans designed to evaluate these effects have not been performed.

Read the Comtan (entacapone) Side Effects Center for a complete guide to possible side effects

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 11-26%], and the INR values increased on average by 13% [Cl90 6-19%]. Nevertheless, cases of significantly increased INR in patients concomitantly using warfarin have been reported during the postapproval use of Comtan. Therefore, monitoring of INR is recommended when entacapone treatment is initiated or when the dose is increased for patients receiving warfarin.

Protein Binding

Entacapone is highly protein bound (98%). In vitro studies have shown no binding displacement between entacapone and other highly bound drugs, such as warfarin, salicylic acid, phenylbutazone, and diazepam.

Drugs Metabolized By Catechol-O-methyltransferase (COMT)

See WARNINGS.

Hormone levels

Levodopa is known to depress prolactin secretion and increase growth hormone levels. Treatment with entacapone coadministered with levodopa and dopa decarboxylase inhibitor does not change these effects.

Effect Of Entacapone On The Metabolism Of Other Drugs

See WARNINGS regarding concomitant use of Comtan and non-selective MAO inhibitors.

No interaction was noted with the MAO-B inhibitor selegiline in two multiple-dose interaction studies when entacapone was coadministered with a levodopa and dopa decarboxylase inhibitor (n=29). More than 600 patients with Parkinson's disease in clinical studies have used selegiline in combination with entacapone and levodopa and dopa decarboxylase inhibitor.

As most entacapone excretion is via the bile, caution should be exercised when drugs known to interfere with biliary excretion, glucuronidation, and intestinal beta-glucuronidase are given concurrently with entacapone. These include probenecid, cholestyramine, and some antibiotics (e.g., erythromycin, rifampicin, ampicillin and chloramphenicol).

No interaction with the tricyclic antidepressant imipramine was shown in a single-dose study with entacapone without coadministered levodopa and dopa-decarboxylase inhibitor.

Read the Comtan Drug Interactions Center for a complete guide to possible interactions

Last reviewed on RxList: 6/27/2014
This monograph has been modified to include the generic and brand name in many instances.

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Comtan - User Reviews

Comtan User Reviews

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Report Problems to the Food and Drug Administration

 

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.


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