Description: Tolcapone is a reversible peripheral catechol-O-methyltransferase (COMT) inhibitor used as an additional drug to levodopa/dopa-decarboxylase inhibitor therapy for the symptomatic treatment of Parkinsonian syndromes or for those experiencing ‘end-of-dose’ deterioration.


Absorption: Rapidly absorbed from the GI tract. Peak plasma concentration: within 2 hr. Absolute bioavailability: 65%. Food delays and decreases the absorption.

Distribution: Protein-binding: >99% (mainly albumin). Not widely distributed into body tissues.

Metabolism: Extensively metabolised, mainly by conjugation to inactive glucuronide, some by catechol-O-methyltransferase and cytochrome P450 isoenzymes CYP3A4 and CYP2A6.

Excretion: Excreted via urine (60%) and faeces. Elimination half-life: 2-3 hr.

This medication, with other medications (levodopa/carbidopa), treats Parkinson’s disease. Tolcapone is a COMT inhibitor that blocks a certain natural substance (COMT enzyme) that breaks down levodopa in the body. This effect allows the levodopa to last longer in the system so that it doesn’t wear off before the next dose.

How to use tolcapone

Take this medication by mouth with or without food, usually 3 times daily or as directed by your doctor. You will start on a low dose. Your doctor may increase your dosage after 3 weeks if he or she thinks that you will benefit from a higher dose.

Dosage is based on your medical condition and response to therapy.

Use this medication regularly to get the most benefit from it. To help you remember, take it at the same times each day. Do not suddenly stop taking this medication unless instructed to do so by your doctor. Doing so may cause your Parkinson’s symptoms to become much worse.

Tell your doctor if your condition persists or worsens (such as your Parkinson’s symptoms are not controlled).

Rarely, tolcapone has caused a severe (sometimes fatal) liver problem (liver failure).

Before and during treatment with tolcapone, you will have certain blood tests (liver function tests) every few weeks to monitor for liver problems.

Tell your doctor or pharmacist promptly if any of these effects persist or worsen:

  • nausea/vomiting
  • unwanted/uncontrolled movements
  • diarrhea
  • headache
  • drowsiness
  • trouble sleeping
  • increased number of dreams
  • increased sweating
  • dry mouth
  • gas
  • abdominal pain

Some people taking tolcapone have fallen asleep suddenly during their usual daily activities (such as talking on the phone, driving).

Tell your doctor right away if you have any serious side effects, including:

  • easy bleeding/bruising
  • chest pain
  • fast/irregular heartbeat
  • fever
  • mental/mood changes (such as agitation, confusion, hallucinations)
  • unusual strong urges (such as increased gambling, increased sexual urges)
  • muscle pain/soreness/stiffness/weakness
  • pain/trouble with breathing

A very serious allergic reaction to this drug is rare.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.


  • Allergic reaction to this medication
  • Patients with medical history of:
    • alcoholism
    • low blood pressure
    • Parkinson’s with severe movement problems
    • mental/mood disorders (such as psychosis, schizophrenia)
    • liver problems
    • history of a certain muscle problem (rhabdomyolysis)
    • fever confusion caused by any drug
  • May make you dizzy or drowsy
  • Tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products) before having surgery
  • Older adults may be more sensitive to drowsiness, confusion, and hallucinations
  • Used only when clearly needed during pregnancy

Consult your doctor regarding the precautions mentioned above.


Certain MAO inhibitors (isocarboxazid, linezolid, methylene blue, moclobemide, phenelzine, procarbazine, tranylcypromine) may interact with this drug. Other MAO inhibitors (selegiline, rasagiline) may be used cautiously with close monitoring by your doctor.

Tolcapone can affect how these drugs work (not a complete list):

  • apomorphine
  • dobutamine
  • methyldopa

Tell your doctor or pharmacist if you are taking other products that cause drowsiness including alcohol, antihistamines (such as cetirizine, diphenhydramine), drugs for sleep or anxiety (such as alprazolam, diazepam, zolpidem), muscle relaxants, and narcotic pain relievers (such as codeine).

This document does not contain all possible interactions. Keep a list of all the products you use. Share this list with your doctor and pharmacist to lessen your risk for serious medication problems.


If overdose is suspected, contact a poison control center or emergency room immediately.


Do not share this medication with others.

Laboratory and/or medical tests (such as liver function tests) should be performed before you start tolcapone and periodically during your treatment to monitor your progress or check for side effects. Consult your doctor for more details.

People with Parkinson’s disease may have an increased risk for developing skin cancer (melanoma). Tell your doctor promptly if you notice a change in the appearance or size of moles or other unusual skin changes. Ask your doctor if you should have regular skin exams.

Missed Dose

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up.


Store at room temperature between 68-77 degrees F (20-25 degrees C) away from light and moisture. Do not store in the bathroom. Keep all medicines away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company for more details about how to safely discard your product.


There are no brands containing this molecule.

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