How does this medication work? What will it do for me?

Entacapone belongs to a group of medications called catechol-O-methyl transferase (COMT) inhibitors. It is used along with levodopa-carbidopa or levodopa-benserazide to treat Parkinson's disease.

By inhibiting COMT enzymes that normally break down levodopa in the body, entacapone increases the amount of levodopa reaching the brain. This reduces the end-of-dose "wearing off" effect that some people taking levodopa may experience, thereby minimizing fluctuations in symptoms of Parkinson's disease. When taken on its own, entacapone has no effect on symptoms of Parkinson's disease.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

Each brownish-orange, unscored, oval-shaped, film-coated tablet, embossed with "COMTAN" on one side, contains entacapone 200 mg. Nonmedicinal ingredients: croscarmellose sodium, hydrogenated vegetable oil, magnesium stearate, mannitol, and microcrystalline cellulose; coating: glycerol 85%, hydroxypropylmethyl cellulose, magnesium stearate, polysorbate 80, red iron oxide, sucrose, titanium dioxide, and yellow iron oxide.

How should I use this medication?

Entacapone is to be taken together with either levodopa-carbidopa or levodopa-benserazide to treat people with Parkinson's disease who experience end-of-dose "wearing off" of levodopa. End-of-dose "wearing off" refers to a decrease in the amount of time that levodopa is effective, which results in fluctuations in Parkinson's disease symptoms.

The recommended dose of entacapone is 200 mg taken with each levodopa-carbidopa or levodopa-benserazide dose, up to 8 times daily.

This medication can be taken with or without food. Swallow the tablets whole. Do not crush or chew the tablets.

This medication has no effect on symptoms of Parkinson's disease when taken alone.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss taking a dose of entacapone with your levodopa dose, skip that dose and take your next entacapone dose with your next levodopa dose. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not take entacapone if you:

  • are allergic to entacapone or any ingredients of the medication
  • are taking or have taken a non-selective monoamine oxidase inhibitor (MAOI) within the last 2 weeks (e.g., phenelzine, tranylcypromine)
  • have a previous history of neuroleptic malignant syndrome or rhabdomyolysis
  • have liver impairment
  • have pheochromocytoma (a tumour in the adrenal glands)
  • have active heart, lung, kidney, blood, or hormonal disease
  • have narrow-angle glaucoma
  • have or have had skin lesions that may be melanoma
  • have any condition where epinephrine, norepinephrine, isoprenaline or dopamine should not be given

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • constipation
  • darkened colour of sweat, saliva, or urine
  • decrease in weight
  • decreased appetite
  • diarrhea
  • dizziness
  • dry mouth
  • falling
  • fatigue
  • fever
  • headache
  • increased sweating
  • involuntary movements
  • muscle pain or cramps
  • nausea
  • nightmares
  • sensation of spinning
  • tremor
  • trouble sleeping
  • vomiting

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • chest pain
  • excessive daytime sleepiness
  • difficult urination
  • hallucinations (hearing or seeing things that aren't there)
  • sexual dysfunction
  • signs of colitis (inflammation of the digestive tract; persistent diarrhea, abdominal cramping)
  • signs of depression (e.g., changes in sleeping or appetite, loss of interest in activities, poor concentration, feelings of guilt)
  • signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
  • signs of low blood pressure (e.g., dizziness, lightheadedness)
  • signs of muscle breakdown (e.g., muscle weakness, pain, bruising, confusion)
  • suddenly falling asleep
  • unusual and uncontrolled muscle movement of the body (including face, tongue, arms, hands, head, upper body)
  • unusual tiredness or weakness
  • unusual weight gain or loss
  • vision changes (e.g., blurred vision, dilated (large) pupils, double-vision)
  • worsening symptoms of Parkinson's disease

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • signs of heart attack (e.g., sudden chest pain or pain radiating to back, down arm, or jaw; sensation of fullness of the chest; nausea; vomiting; sweating; anxiety)
  • signs of neuroleptic malignant syndrome (e.g., agitation; anxiety; confusion; fast, irregular, or pounding heartbeat; increased body temperature; muscle rigidity)
  • signs of a severe skin reaction (i.e., blistering, peeling, a rash covering a large area of the body, a rash that spreads quickly, or a rash combined with fever or discomfort)
  • signs of a serious allergic reaction (i.e., abdominal cramps, difficulty breathing, rash, hives, or swelling of the face and throat)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin taking a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should take this medication.

Behavioural and mood changes: This medication may cause mood and psychiatric changes, including hallucinations, hypersexuality, pathological gambling, and increased libido. Tell your doctor as soon as possible if you notice any unusual changes in your behaviour, have thoughts of harming yourself, or feel depressed.

If you have depression or a history of depression, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. If you experience symptoms of depression such as poor concentration, changes in weight, changes in sleep, decreased interest in activities, or notice them in a family member who is taking this medication, contact your doctor as soon as possible.

Diarrhea: Diarrhea is a common side effect of this medication. It may appear as early as the first week of starting treatment or many months after starting treatment. For some people, the diarrhea causes weight loss. If you notice any weight loss or have excessive diarrhea, contact your doctor.

Dizziness/reduced alertness: This medication may cause low blood pressure or dizziness and lightheadedness when rising from a lying or sitting position. People taking medications that can cause dizziness should rise slowly from sitting or lying down to reduce the possibility of severe dizziness or fainting. Do not drive, operate machinery, or perform other hazardous tasks until you have determined how this medication affects you.

Fructose intolerance: This medication contains fructose. If you have fructose intolerance, glucose-galactose malabsorption, or sucrase-isomaltase insufficiency, you should not take this medication. Talk to your doctor.

Heart disease: This medication may cause an increase in the risk of heart attack or heart disease. If you have a history of heart disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function: Liver disease or reduced liver function may cause this medication to build up in the body, causing side effects. This medication is not recommended for people with liver problems.

Melanoma: People with Parkinson's disease may be at increased risk of developing melanoma (a type of skin cancer). It is not known if this increased risk is due to Parkinson's disease or to the medications used to treat Parkinson's disease. Your doctor will monitor you for skin cancer while you are taking this medication. Talk to your doctor if you have any concerns.

Neuroleptic malignant syndrome (NMS): This medication may cause a potentially fatal reaction called neuroleptic malignant syndrome (NMS). If you develop symptoms of NMS, such as muscle stiffness, fever, confusion, sweating, or irregular heartbeat, stop taking this medication and seek immediate medical attention.

Prostate cancer: A recent study has shown an increase in the number of cases of prostate cancer among men who have taken levodopa/carbidopa with or without entacapone for approximately 3 years. Although it is not clear whether this increased risk of prostate cancer is due to the medication or something else, it is important to have regular prostate examinations while taking medications for Parkinson's Disease.

Rhabdomyolysis (muscle breakdown): Occasionally, this medication may cause rapid breakdown of muscle tissue. If you notice signs of muscle weakness or pain, high body temperature, unexpected bruising, confusion, or difficulty passing urine, contact your doctor immediately.

Stopping this medication: Stopping this medication too quickly can cause potentially life-threatening side effects. Before stopping this medication, discuss the risks and benefits with your doctor. Do not stop taking this medication until you have spoken with your doctor first.

Sudden onset of sleep: There are reports of people who take this combination medication treatment (entacapone with levodopa - carbidopa) falling asleep without prior warning or drowsiness. If you have a sleep disorder, discuss this with your doctor. If you experience drowsiness while taking this medication, avoid driving or using machinery.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast feeding: It is not known if entacapone passes into breast milk. If you are breast-feeding and are using this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children less than 18 years of age.

What other drugs could interact with this medication?

There may be an interaction between entacapone and any of the following:

  • alcohol
  • antihistamines (e.g., chlorpheniramine, diphenhydramine, hydroxyzine)
  • anti-seizure medications (e.g., carbamazepine, gabapentin, lamotrigine, phenytoin, phenobarbital)
  • antipsychotics (e.g., fluphenazine, perphenazine, quetiapine, risperidone)
  • apomorphine
  • azelastine
  • barbiturates (e.g., butalbital, phenobarbital)
  • benzodiazepines (e.g., alprazolam, diazepam, lorazepam)
  • brimonidine
  • buprenorphine
  • buspirone
  • cannabis
  • chloral hydrate
  • clonidine
  • dobutamine
  • dopamine
  • epinephrine
  • flibanserin
  • flunarizine
  • guanfacine
  • iron supplements
  • isoproterenol
  • lemborexant
  • linezolid
  • MAO inhibitors (e.g., phenelzine, rasagiline, selegiline, tranylcypromine)
  • methadone
  • methyldopa
  • methylene blue
  • metoclopramide
  • mirtazapine
  • muscle relaxants (e.g., baclofen, cyclobenzaprine, methocarbamol, orphenadrine)
  • narcotic medications (e.g., codeine, fentanyl, morphine)
  • norepinephrine
  • pramipexole
  • ropinirole
  • scopolamine
  • selective serotonin reuptake inhibitors (e.g., citalopram, fluoxetine, paroxetine, sertraline)
  • thalidomide
  • tapentadol
  • tramadol
  • tricyclic antidepressants (e.g., amitriptyline, clomipramine, desipramine, trimipramine)
  • valerian
  • warfarin
  • zolpidem
  • zopiclone

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.

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