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Comtan
Overview
What is Comtan?
Comtan (entacapone) is available as tablets containing 200 mg entacapone.
Entacapone is an inhibitor of catechol--methyltransferase (COMT), used in the treatment of Parkinson's disease as an adjunct to levodopa and carbidopa therapy. It is a nitrocatechol-structured compound with a relative molecular mass of 305.29. The chemical name of entacapone is (E)-2-cyano-3-(3,4-dihydroxy-5-nitrophenyl)-N,N-diethyl-2-propenamide. Its empirical formula is CHNO and its structural formula is:
The inactive ingredients of the Comtan tablet are microcrystalline cellulose, mannitol, croscarmellose sodium, hydrogenated vegetable oil, hydroxypropyl methylcellulose, polysorbate 80, glycerol 85%, sucrose, magnesium stearate, yellow iron oxide, red iron oxide, and titanium dioxide.
What does Comtan look like?
What are the available doses of Comtan?
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What should I talk to my health care provider before I take Comtan?
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How should I use Comtan?
Comtan is indicated as an adjunct to levodopa and carbidopa to treat end-of-dose "wearing-off" in patients with Parkinson's disease (see ).
Comtan's effectiveness has not been systematically evaluated in patients with Parkinson's disease who do not experience end-of-dose "wearing-off".
The recommended dose of Comtan (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.
Comtan 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.)
Comtan can be combined with both the immediate and sustained-release formulations of levodopa and carbidopa.
Comtan may be taken with or without food (see).
What interacts with Comtan?
Comtan is contraindicated in patients who have demonstrated hypersensitivity to the drug or its ingredients.
What are the warnings of Comtan?
There are no adequate and well-controlled studies in pregnant women. If paclitaxel is used during pregnancy, or if the patient becomes pregnant while receiving this drug, the patient should be apprised of the potential hazard to the fetus. Women of child-bearing potential should be advised to avoid becoming pregnant.
Monoamine oxidase (MAO) and COMT are the two major enzyme systems involved in the metabolism of catecholamines. It is theoretically possible, therefore, that the combination of Comtan (entacapone) and a non-selective MAO inhibitor (e.g., phenelzine and tranylcypromine) would result in inhibition of the majority of the pathways responsible for normal catecholamine metabolism. For this reason, patients should ordinarily not be treated concomitantly with Comtan and a non-selective MAO inhibitor.
Entacapone can be taken concomitantly with a selective MAO-B inhibitor (e.g., selegiline).
Drugs Metabolized By Catechol-O-Methyltransferase (COMT)
When a single 400 mg dose of entacapone was given with intravenous isoprenaline (isoproterenol) and epinephrine without coadministered levodopa and dopa decarboxylase inhibitor, the overall mean maximal changes in heart rate during infusion were about 50% and 80% higher than with placebo, for isoprenaline and epinephrine, respectively.
Therefore, drugs known to be metabolized by COMT, such as isoproterenol, epinephrine, norepinephrine, dopamine, dobutamine, alpha-methyldopa, apomorphine, isoetherine, and bitolterol should be administered with caution in patients receiving entacapone regardless of the route of administration (including inhalation), as their interaction may result in increased heart rates, possible arrhythmias, and excessive changes in blood pressure.
Ventricular tachycardia was noted in one 32-year-old healthy male volunteer in an interaction study after epinephrine infusion and oral entacapone administration. Treatment with propranolol was required. A causal relationship to entacapone administration appears probable but cannot be attributed with certainty.
Falling Asleep During Activities of Daily Living and Somnolence
Patients with Parkinson's disease treated with Comtan, which increases plasma levodopa levels, or with levodopa have reported suddenly falling asleep without prior warning of sleepiness while engaged in activities of daily living (including the operation of motor vehicles). Some of these episodes resulted in accidents. Although many of these patients reported somnolence while on Comtan, some did not perceive warning signs, such as excessive drowsiness, and believed that they were alert immediately prior to the event. Some of these events have been reported as late as one year after initiation of treatment.
The risk of somnolence was increased (Comtan 2% and placebo 0%) in controlled studies. It has been reported that falling asleep while engaged in activities of daily living always 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. Patients should be advised to exercise caution while driving, operating machines, or working at heights during treatment with Comtan. Patients who have already experienced somnolence and/or an episode of sudden sleep onset should not participate in these activities during treatment with Comtan.
Before initiating treatment with Comtan, advise patients of the potential to develop drowsiness and specifically ask about factors that may increase this risk such as concomitant use of sedating medications and the presence of sleep disorders. If a patient develops daytime sleepiness or episodes of falling asleep during activities that require active participation (e.g., conversations, eating, etc.), Comtan should ordinarily be discontinued (see for guidance on discontinuing Comtan). If the decision is made to continue Comtan, patients should be advised not to drive and to avoid other potentially dangerous activities. There is insufficient information to establish whether dose reduction will eliminate episodes of falling asleep while engaged in activities of daily living.
What are the precautions of Comtan?
Hypotension, Orthostatic Hypotension, and Syncope
Dopaminergic therapy in Parkinson's disease patients has been associated with orthostatic hypotension. Entacapone enhances levodopa bioavailability and, therefore, might be expected to increase the occurrence of orthostatic hypotension. In controlled studies, approximately 1.2% and 0.8% of 200 mg entacapone and placebo patients, respectively, reported at least one episode of syncope. Reports of syncope were generally more frequent in patients in both treatment groups who had an episode of documented hypotension.
Hallucinations and Psychotic-Like Behavior
Dopaminergic therapy in patients with Parkinson's disease has been associated with hallucinations. In clinical studies, hallucinations led to drug discontinuation and premature withdrawal in 0.8% and 0% of patients treated with 200 mg Comtan and placebo, respectively. Hallucinations led to hospitalization in 1.0% and 0.3% of patients in the 200 mg Comtan and placebo groups, respectively. Agitation occurred in 1% of patients treated with COMTAN and 0% treated with placebo.
Postmarketing reports indicate that patients may experience new or worsening mental status and behavioral changes, which may be severe, including psychotic-like behavior during Comtan treatment or after starting or increasing the dose of Comtan. Other drugs prescribed to improve the symptoms of Parkinson's disease can have similar effects on thinking and behavior. Abnormal thinking and behavior can cause paranoid ideation, delusions, hallucinations, confusion, disorientation, aggressive behavior, agitation, and delirium. Psychotic-like behaviors were also observed during the clinical development of Comtan.
Patients with a major psychotic disorder should ordinarily not be treated with Comtan because of the risk of exacerbating psychosis. In addition, certain medications used to treat psychosis may exacerbate the symptoms of Parkinson's disease and may decrease the effectiveness of Comtan (see ).
Impulse Control and Compulsive Behaviors
Postmarketing reports suggest that patients treated with anti-Parkinson medications can experience intense urges to gamble, increased sexual urges, intense urges to spend money uncontrollably, and other intense urges. Patients may be unable to control these urges while taking one or more of the medications that are used for the treatment of Parkinson's disease and that increase central dopaminergic tone, including Comtan taken with levodopa and carbidopa. In some cases, although not all, these urges were reported to have stopped when the dose of anti-Parkinson medications was reduced or 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 entacapone. Physicians should consider dose reduction or stopping Comtan if a patient develops such urges while taking Comtan.
Diarrhea and Colitis
In clinical studies, diarrhea developed in 60 of 603 (10%) and 16 of 400 (4%) of patients treated with 200 mg Comtan and placebo, respectively. In patients treated with Comtan, diarrhea was generally mild to moderate in severity (8.6%) but was regarded as severe in 1.3%. Diarrhea resulted in withdrawal in 10 of 603 (1.7%) patients, 7 (1.2%) with mild and moderate diarrhea and 3 (0.5%) with severe diarrhea. Diarrhea generally resolved after discontinuation of Comtan. Two patients with diarrhea were hospitalized. Typically, diarrhea presents within 4 weeks to 12 weeks after entacapone is started, but it may appear as early as the first week and as late as many months after the initiation of treatment. Diarrhea may be associated with weight loss, dehydration, and hypokalemia.
Postmarketing experience has shown that diarrhea may be a sign of drug-induced microscopic colitis, primarily lymphocytic colitis. In these cases diarrhea has usually been moderate to severe, watery, and non-bloody, at times associated with dehydration, abdominal pain, weight loss, and hypokalemia. In the majority of cases, diarrhea and other colitis-related symptoms resolved or significantly improved when Comtan treatment was stopped. In some patients with biopsy confirmed colitis, diarrhea had resolved or significantly improved after discontinuation of Comtan but recurred after retreatment with Comtan.
If prolonged diarrhea is suspected to be related to Comtan, the drug should be discontinued and appropriate medical therapy considered. If the cause of prolonged diarrhea remains unclear or continues after stopping entacapone, then further diagnostic investigations including colonoscopy and biopsies should be considered.
Dyskinesia
Comtan may potentiate the dopaminergic side effects of levodopa and may cause or exacerbate preexisting dyskinesia. Although decreasing the dose of levodopa may ameliorate this side effect, many patients in controlled studies continued to experience frequent dyskinesia despite a reduction in their dose of levodopa. The incidence of dyskinesia was 25% for treatment with Comtan and 15% for placebo. The incidence of study withdrawal for dyskinesia was 1.5% for 200 mg Comtan and 0.8% for placebo.
Other Events Reported With Dopaminergic Therapy
The events listed below are events associated with the use of drugs that increase dopaminergic activity.
Rhabdomyolysis
Cases of severe rhabdomyolysis have been reported following the approval of Comtan. Although the reactions typically occurred while patients were treated with Comtan, the complicated nature of these cases makes it difficult to determine what role, if any, Comtan played in their pathogenesis. Severe prolonged motor activity including dyskinesia may account for rhabdomyolysis. Signs and symptoms include fever, alteration of consciousness, myalgia, increased values of creatine phosphokinase (CPK) and myoglobin.
Hyperpyrexia and Confusion
Cases of a symptom complex resembling neuroleptic malignant syndrome (NMS) characterized by elevated temperature, muscular rigidity, altered consciousness, and elevated CPK have been reported in association with the rapid dose reduction or withdrawal of other dopaminergic drugs. In most of these cases, symptoms began after abrupt discontinuation of treatment with entacapone or reduction of its dose, or after the initiation of treatment with entacapone. The complicated nature of these cases makes it difficult to determine what role, if any, Comtan may have played in their pathogenesis. No cases have been reported following the abrupt withdrawal or dose reduction of entacapone treatment during clinical studies.
Prescribers should exercise caution when discontinuing entacapone treatment. When considered necessary, withdrawal should proceed slowly. If the decision is made to discontinue treatment with Comtan, recommendations include monitoring the patient closely and adjusting other dopaminergic treatments as needed. This syndrome should be considered in the differential diagnosis for any patient who develops a high fever or severe rigidity. Tapering Comtan has not been systematically evaluated.
Fibrotic Complications
Cases of retroperitoneal fibrosis, pulmonary infiltrates, pleural effusion, and pleural thickening have been reported in some patients treated with ergot derived dopaminergic agents. These complications may resolve when the drug is discontinued, but complete resolution does not always occur. Although these adverse events are believed to be related to the ergoline structure of these compounds, whether other, nonergot derived drugs (e.g., entacapone) that increase dopaminergic activity can cause them is unknown. It should be noted that the expected incidence of fibrotic complications is so low that even if entacapone caused these complications at rates similar to those attributable to other dopaminergic therapies, it is unlikely that it would have been detected in a cohort of the size exposed to entacapone. Four cases of pulmonary fibrosis were reported during clinical development of entacapone; three of these patients were also treated with pergolide and one with bromocriptine. The duration of treatment with entacapone ranged from 7 months to 17 months.
Melanoma
Epidemiological studies have shown that patients with Parkinson's disease have a higher risk (2- to approximately 6-fold higher) of developing melanoma than the general population. Whether the increased risk observed was due to Parkinson's disease or other factors, such as drugs used to treat Parkinson's disease, is unclear.
For the reasons stated above, patients and providers are advised to monitor for melanomas frequently and on a regular basis when using Comtan for indication. Ideally, periodic skin examinations should be performed by appropriately qualified individuals (e.g., dermatologists).
Renal Toxicity
In a 1-year toxicity study, entacapone (plasma exposure 20 times that in humans receiving the maximum recommended daily dose of 1,600 mg) caused an increased incidence of nephrotoxicity in male rats that was characterized by regenerative tubules, thickening of basement membranes, infiltration of mononuclear cells, and tubular protein casts. These effects were not associated with changes in clinical chemistry parameters, and there is no established method for monitoring for the possible occurrence of these lesions in humans. Although this toxicity could represent a species-specific effect, there is not yet evidence that this is so.
Hepatic Impairment
Patients with hepatic impairment should be treated with caution. The AUC and C of entacapone approximately doubled in patients with documented liver disease compared to controls (seeand).
Information for Patients
Instruct patients to take Comtan only as prescribed.
Inform patients that hallucinations and/or other psychotic-like behavior can occur.
Advise patients that they may develop postural (orthostatic) hypotension with or without symptoms such as dizziness, nausea, syncope, and sweating. Hypotension may occur more frequently during initial therapy. Accordingly, patients should be cautioned against rising rapidly after sitting or lying down, especially if they have been doing so for prolonged periods, and especially at the initiation of treatment with Comtan.
Advise patients that they should neither drive a car nor operate other complex machinery until they have gained sufficient experience on Comtan to gauge whether or not it affects their mental and/or motor performance adversely. Warn patients about the possibility of sudden onset of sleep during daily activities, in some cases without awareness or warning signs, when they are taking dopaminergic agents, including Comtan. Because of the possible additive sedative effects, caution should be used when patients are taking other CNS depressants in combination with Comtan.
Inform patients that nausea may occur, especially at the initiation of treatment with Comtan.
Inform patients that diarrhea may occur with Comtan and it may have a delayed onset. Sometimes prolonged diarrhea may be caused by colitis (inflammation of the large intestine). Patients with diarrhea should drink fluids to maintain adequate hydration and monitor for weight loss. If diarrhea associated with Comtan is prolonged, discontinuing the drug is expected to lead to resolution, if diarrhea continues after stopping entacapone, further diagnostic investigations may be needed.
Advise patients about the possibility of an increase in dyskinesia.
Tell patients that treatment with entacapone may cause a change in the color of their urine (a brownish orange discoloration) that is not clinically relevant. In controlled studies, 10% of patients treated with Comtan reported urine discoloration compared to 0% of placebo patients.
Although Comtan has not been shown to be teratogenic in animals, it is always given in conjunction with levodopa and carbidopa, which is known to cause visceral and skeletal malformations in rabbits. Accordingly, patients should be advised to notify their physicians if they become pregnant or intend to become pregnant during therapy (see).
Entacapone is excreted into maternal milk in rats. Because of the possibility that entacapone may be excreted into human maternal milk, advise patients to notify their physicians if they intend to breastfeed or are breastfeeding an infant.
Tell patients and family members to notify their healthcare practitioner if they notice that the patient develops unusual urges or behaviors.
Laboratory Tests
Comtan is a chelator of iron. The impact of entacapone on the body's iron stores is unknown; however, a tendency towards decreasing serum iron concentrations was noted in clinical studies. In a controlled clinical study serum ferritin levels (as marker of iron deficiency and subclinical anemia) were not changed with entacapone compared to placebo after one year of treatment and there was no difference in rates of anemia or decreased hemoglobin levels.
Special Populations
Patients with hepatic impairment should be treated with caution (see,).
Drug Interactions
In vitro
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 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%). 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.
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
Seeregarding 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.
Carcinogenesis
Two-year carcinogenicity studies of entacapone were conducted in mice and rats. In mice, no increase in tumors was observed at oral doses of 100, 200 and 400 mg/kg/day. At the highest dose tested, plasma exposures (AUC) were 4 times higher than that in humans at the maximum recommended daily dose (MRDD) of 1,600 mg. In rats administered oral doses of 20, 90, or 400 mg/kg/day, an increased incidence of renal tubular adenomas and carcinomas was observed in males at the highest dose tested. Plasma AUCs at the higher dose not associated with increased renal tumors (90 mg/kg/day) were approximately 5 times that in humans at the MRDD of entacapone.
The carcinogenic potential of entacapone administered in combination with levodopa and carbidopa has not been evaluated.
Mutagenesis
Entacapone was mutagenic and clastogenic in the mouse assay in the presence and absence of metabolic activation, and was clastogenic in cultured human lymphocytes in the presence of metabolic activation. Entacapone, either alone or in combination with levodopa and carbidopa, was not clastogenic in the mouse micronucleus test or mutagenic in the bacterial reverse mutation assay (Ames test).
Impairment of Fertility
Entacapone did not impair fertility or general reproductive performance in rats treated with up to 700 mg/kg/day (plasma AUCs 28 times those in humans receiving the MRDD of 1,600 mg). Delayed mating, but no fertility impairment, was evident in female rats treated with 700 mg/kg/day of entacapone.
Pregnancy
In embryofetal development studies, entacapone was administered to pregnant animals throughout organogenesis at doses of up to 1,000 mg/kg/day in rats and 300 mg/kg/day in rabbits. Increased incidences of fetal variations were evident in litters from rats treated with the highest dose, in the absence of overt signs of maternal toxicity. The maternal plasma drug exposure (AUC) associated with this dose was approximately 34 times the estimated plasma exposure in humans receiving the maximum recommended daily dose (MRDD) of 1,600 mg. Increased frequencies of abortions, late and total resorptions, and decreased fetal weights were observed in the litters of rabbits treated with maternally toxic doses of 100 mg/kg/day (plasma AUCs 0.4 times those in humans receiving the MRDD) or greater. There was no evidence of teratogenicity in these studies.
However, when entacapone was administered to female rats prior to mating and during early gestation, an increased incidence of fetal eye anomalies (macrophthalmia, microphthalmia, anophthalmia) was observed in the litters of dams treated with doses of 160 mg/kg/day (plasma AUCs 7 times those in humans receiving the MRDD) or greater, in the absence of maternal toxicity. Administration of up to 700 mg/kg/day (plasma AUCs 28 times those in humans receiving the MRDD) to female rats during the latter part of gestation and throughout lactation produced no evidence of developmental impairment in the offspring.
Entacapone is always given concomitantly with levodopa and carbidopa, which is known to cause visceral and skeletal malformations in rabbits. The teratogenic potential of entacapone in combination with levodopa and carbidopa was not assessed in animals.
There is no experience from clinical studies regarding the use of Comtan in pregnant women. Therefore, Comtan should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Nursing Women
In animal studies, entacapone was excreted into maternal rat milk.
It is not known whether entacapone is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when entacapone is administered to a nursing woman.
Pediatric Use
Safety and effectiveness in pediatric patients have not been established.
What are the side effects of Comtan?
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 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 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 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 Comtan group, compared to placebo. In these studies, either Comtan or placebo was added to levodopa and carbidopa (or levodopa and benserazide).
| SYSTEM ORGAN CLASS | Comtan | 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 Comtan 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 Comtan exposure.
Hepatitis with mainly cholestatic features has been reported.
What should I look out for while using Comtan?
Comtan is contraindicated in patients who have demonstrated hypersensitivity to the drug or its ingredients.
Monoamine oxidase (MAO) and COMT are the two major enzyme systems involved in the metabolism of catecholamines. It is theoretically possible, therefore, that the combination of Comtan (entacapone) and a non-selective MAO inhibitor (e.g., phenelzine and tranylcypromine) would result in inhibition of the majority of the pathways responsible for normal catecholamine metabolism. For this reason, patients should ordinarily not be treated concomitantly with Comtan and a non-selective MAO inhibitor.
Entacapone can be taken concomitantly with a selective MAO-B inhibitor (e.g., selegiline).
What might happen if I take too much Comtan?
The postmarketing data include several cases of overdose. The highest reported dose of entacapone was at least 40,000 mg. The acute symptoms and signs commonly seen in these cases included somnolence and decreased activity, states related to depressed level of consciousness (e.g., coma, confusion and disorientation) and discolorations of skin, tongue, and urine, as well as restlessness, agitation, and aggression.
COMT inhibition by entacapone treatment is dose-dependent. A massive overdose of Comtan (entacapone) may theoretically produce a 100% inhibition of the COMT enzyme in humans, thereby preventing the metabolism of endogenous and exogenous catechols.
The highest daily dose given to humans was 2,400 mg, administered in one study as 400 mg six times daily with levodopa and carbidopa for 14 days in 15 Parkinson's disease patients, and in another study as 800 mg three times daily for 7 days in 8 healthy volunteers. At this daily dose, the peak plasma concentrations of entacapone averaged 2.0 mcg per mL (at 45 minutes, compared to 1.0 mcg per mL and 1.2 mcg per mL with 200 mg entacapone at 45 minutes). Abdominal pain and loose stools were the most commonly observed adverse events during this study. Daily doses as high as 2,000 mg Comtan have been administered as 200 mg 10 times daily with levodopa and carbidopa or levodopa and benserazide for at least 1 year in 10 patients, for at least 2 years in 8 patients and for at least 3 years in 7 patients. Overall, however, clinical experience with daily doses above 1,600 mg is limited.
The range of lethal plasma concentrations of entacapone based on animal data was 80 mcg per mL to 130 mcg per mL in mice. Respiratory difficulties, ataxia, hypoactivity, and convulsions were observed in mice after high oral (gavage) doses.
How should I store and handle Comtan?
Comtan (entacapone) is supplied as 200 mg film-coated tablets for oral administration. The oval-shaped tablets are brownish-orange, unscored, and embossed "Comtan" on one side. Tablets are provided in HDPE containers as follows:
Clinical Information
Chemical Structure
No Image foundClinical Pharmacology
Entacapone is a selective and reversible inhibitor of COMT.
In mammals, COMT is distributed throughout various organs with the highest activities in the liver and kidney. COMT also occurs in the heart, lung, smooth and skeletal muscles, intestinal tract, reproductive organs, various glands, adipose tissue, skin, blood cells, and neuronal tissues, especially in glial cells. COMT catalyzes the transfer of the methyl group of S-adenosyl-L-methionine to the phenolic group of substrates that contain a catechol structure. Physiological substrates of COMT include dopa, catecholamines (dopamine, norepinephrine, and epinephrine) and their hydroxylated metabolites. The function of COMT is the elimination of biologically active catechols and some other hydroxylated metabolites. In the presence of a decarboxylase inhibitor, COMT becomes the major metabolizing enzyme for levodopa, catalyzing the metabolism to 3-methoxy-4-hydroxy-L-phenylalanine (3-OMD) in the brain and periphery.
The mechanism of action of entacapone is believed to be through its ability to inhibit COMT and alter the plasma pharmacokinetics of levodopa. When entacapone is given in conjunction with levodopa and an aromatic amino acid decarboxylase inhibitor, such as carbidopa, plasma levels of levodopa are greater and more sustained than after administration of levodopa and an aromatic amino acid decarboxylase inhibitor alone. It is believed that at a given frequency of levodopa administration, these more sustained plasma levels of levodopa result in more constant dopaminergic stimulation in the brain, leading to greater effects on the signs and symptoms of Parkinson's disease. The higher levodopa levels also lead to increased levodopa adverse effects, sometimes requiring a decrease in the dose of levodopa.
In animals, while entacapone enters the central nervous system (CNS) to a minimal extent, it has been shown to inhibit central COMT activity. In humans, entacapone inhibits the COMT enzyme in peripheral tissues. The effects of entacapone on central COMT activity in humans have not been studied.
Non-Clinical Toxicology
Comtan is contraindicated in patients who have demonstrated hypersensitivity to the drug or its ingredients.Monoamine oxidase (MAO) and COMT are the two major enzyme systems involved in the metabolism of catecholamines. It is theoretically possible, therefore, that the combination of Comtan (entacapone) and a non-selective MAO inhibitor (e.g., phenelzine and tranylcypromine) would result in inhibition of the majority of the pathways responsible for normal catecholamine metabolism. For this reason, patients should ordinarily not be treated concomitantly with Comtan and a non-selective MAO inhibitor.
Entacapone can be taken concomitantly with a selective MAO-B inhibitor (e.g., selegiline).
In vitro
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 Comtan. Therefore, monitoring of INR is recommended when entacapone treatment is initiated or when the dose is increased for patients receiving warfarin.
Dopaminergic therapy in Parkinson's disease patients has been associated with orthostatic hypotension. Entacapone enhances levodopa bioavailability and, therefore, might be expected to increase the occurrence of orthostatic hypotension. In controlled studies, approximately 1.2% and 0.8% of 200 mg entacapone and placebo patients, respectively, reported at least one episode of syncope. Reports of syncope were generally more frequent in patients in both treatment groups who had an episode of documented hypotension.
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 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 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 disorders (2% vs. 1%), diarrhea (2% vs. 0%), dyskinesia and hyperkinesia (2% vs. 1%), nausea (2% vs. 1%), and abdominal pain (1% vs. 0%).
Reference
This information is obtained from the National Institute of Health's Standard Packaging Label drug database.
"https://dailymed.nlm.nih.gov/dailymed/"
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Clonazepam Description Each single-scored tablet, for oral administration, contains 0.5 mg, 1 mg, or 2 mg Clonazepam, USP, a benzodiazepine. Each tablet also contains corn starch, lactose monohydrate, magnesium stearate, microcrystalline cellulose, and povidone. Clonazepam tablets USP 0.5 mg contain Yellow D&C No. 10 Aluminum Lake. Clonazepam tablets USP 1 mg contain Yellow D&C No. 10 Aluminum Lake, as well as FD&C Blue No. 1 Aluminum Lake. Chemically, Clonazepam, USP is 5-(o-chlorophenyl)-1,3-dihydro-7-nitro-2H-1,4-benzodiazepin-2-one. It is a light yellow crystalline powder. It has the following structural formula: C15H10ClN3O3 M.W. 315.72Tips
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A total of 440 drugs (1549 brand and generic names) are known to interact with Imbruvica (ibrutinib). 228 major drug interactions (854 brand and generic names) 210 moderate drug interactions (691 brand and generic names) 2 minor drug interactions (4 brand and generic names) Show all medications in the database that may interact with Imbruvica (ibrutinib).