Tolcapone
Pronunciation: pronunciation varies by local usage.
- Generic name
- tolcapone
- Brand names
- Tasmar
- Drug class
- Catechol-O-methyltransferase (COMT) inhibitor
Availability and supply rules vary by country
Trade names by country: United States
Australia: · Full directory
What tolcapone is and how it works
Uses, formulations, monitoring, and supply rules can differ by patient, product, and country. Follow the exact local product information and professional advice.
Mechanism of action: how tolcapone works
Tolcapone is a reversible catechol-O-methyltransferase (COMT) inhibitor. Tolcapone is highly protein-bound (>99.9%) but does not displace warfarin, phenytoin, tolbutamide, or digitoxin at therapeutic concentrations, and shows no clinically relevant interaction with CYP 2A6, 1A2, 3A4, 2C19, or 2D6 substrates in vitro or in vivo. (1)
What tolcapone is used for
Adjunct to levodopa/carbidopa for idiopathic Parkinson's disease
Specifically for patients with symptom fluctuations who are not responding satisfactorily to, or are not appropriate candidates for, other adjunctive therapies, because of the hepatotoxicity risk. (1)
Before taking tolcapone
Do not take / not appropriate for
- evidence of liver disease. (Contraindication) (1)
- history of tolcapone-induced hepatocellular injury. (Contraindication) (1)
- history of nontraumatic rhabdomyolysis or hyperpyrexia and confusion possibly related to medication. (Contraindication) (1)
- hypersensitivity to tolcapone or product ingredients. (Contraindication) (1)
Tell your clinician about
(1)How to take tolcapone
- Starting dose is 100 mg three times daily, always combined with levodopa/carbidopa — the first tolcapone dose is taken with the first daily levodopa/carbidopa dose, with further doses about 6 and 12 hours later. Your prescriber may increase the dose to a maximum of 200 mg three times daily only if the added benefit is judged to outweigh the increased liver-injury risk. Tolcapone may be taken with or without food, but taking it within 1 hour before or 2 hours after a meal reduces absorption by 10-20%. If substantial clinical benefit is not seen within 3 weeks of starting, your prescriber should withdraw tolcapone. Because abrupt withdrawal or dose lowering has been linked to a rare, serious symptom complex resembling neuroleptic malignant syndrome (fever, confusion, muscle rigidity), any change to your dose or discontinuation of treatment is decided and managed by your prescriber, normally on a gradual schedule.
- This page does not provide a dose calculator. Dosing must follow the prescriber, pharmacist, or product label.
Procedures and treatment changes
Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1)
Missed dose
Because tolcapone is taken alongside carefully timed levodopa/carbidopa doses, contact your prescribing clinician or pharmacist for missed-dose advice rather than adjusting your own schedule.
Overdose
In case of overdose, seek emergency medical attention or contact a poison control center immediately. In a human study of supratherapeutic doses (800 mg three times daily), nausea, vomiting, and dizziness were observed when combined with levodopa/carbidopa. Management is hospitalization and general supportive care; hemodialysis is unlikely to help because tolcapone is highly protein-bound. (1)
Side effects
Side effects and their urgency vary; report severe, persistent, or concerning symptoms to a healthcare professional. Percentages below are from clinical trials comparing tolcapone 100 mg and 200 mg three-times-daily doses against placebo, all as add-on therapy to levodopa/carbidopa.
Dyskinesia (involuntary movements)
Incidence: 42% (100 mg) to 51% (200 mg), versus 20% with placebo
Nausea
Incidence: 30% (100 mg) to 35% (200 mg), versus 18% with placebo
Diarrhea
Incidence: 16% (100 mg) to 18% (200 mg), versus 8% with placebo; typical onset 6-12 weeks after starting; the most common reason for stopping tolcapone; severe in 3-4% of tolcapone-treated patients
Anorexia (reduced appetite)
Incidence: 19% (100 mg) to 23% (200 mg), versus 13% with placebo
Orthostatic hypotension (dizziness on standing)
Incidence: 14% (100 mg) to 13% (200 mg), versus 8% with placebo; syncope (fainting) in 4-5% versus 3% with placebo
Hallucinations
Incidence: 8% (100 mg) to 10% (200 mg), versus 5% with placebo; may be more frequent in patients over 75
Warning signs of possible liver injury
What to notice: Yellowing of the skin or eyes (jaundice); dark urine; persistent nausea, fatigue, or lethargy; loss of appetite; itching; right-upper-abdominal tenderness
What to do: Contact your healthcare provider immediately if any of these occur — do not wait for your next scheduled liver test. (1)
Serious warnings
BOXED WARNING — potentially fatal acute liver failure — serious
Symptoms: BOXED WARNING — potentially fatal acute liver failure: tolcapone carries a US FDA boxed warning because of the risk of fatal, acute fulminant liver failure. It is ordinarily used only in patients with symptom fluctuations who have not responded to, or are not candidates for, other adjunctive therapies. As of a 2005 FDA review, 3 fatal cases had been reported from over 40,000 patient-years of use worldwide, all within the first 6 months of starting treatment; the estimated fatal-liver-failure risk may be 10 to 100 times the background rate in the general population.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (1)
Written risk acknowledgment is required before starting — serious
Symptoms: Written risk acknowledgment is required before starting: your prescriber must fully discuss the liver-failure risk, that no test reliably predicts who is at risk, the required baseline and periodic liver blood tests, and the need to report symptoms of liver injury immediately (persistent nausea, fatigue, lethargy, loss of appetite, jaundice, dark urine, itching, or right-upper-abdominal tenderness) — before you sign a written acknowledgment.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (1)
Tolcapone is contraindicated in active liver disease, a history of tolcapone-related liver injury, a history of nontraumatic rhabdomyolysis, a history of hyperpyrexia and confusion possibly related to medication, or a known allergy to tolcapone or its ingredients — serious
Symptoms: Tolcapone is contraindicated in active liver disease, a history of tolcapone-related liver injury, a history of nontraumatic rhabdomyolysis, a history of hyperpyrexia and confusion possibly related to medication, or a known allergy to tolcapone or its ingredients. Your prescriber must determine your eligibility for tolcapone before prescribing or starting treatment.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (1)
A rare, serious symptom complex resembling neuroleptic malignant syndrome (fever, muscle rigidity, confusion) has been reported with abrupt withdrawal or dose lowering of tolcapone — serious
Symptoms: A rare, serious symptom complex resembling neuroleptic malignant syndrome (fever, muscle rigidity, confusion) has been reported with abrupt withdrawal or dose lowering of tolcapone. Seek immediate medical attention if these symptoms occur. Decisions to reduce or stop tolcapone are made and managed by your prescriber.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (1)
Severe rhabdomyolysis (muscle breakdown), including one fatal case with multi-organ failure, has been reported — serious
Symptoms: Severe rhabdomyolysis (muscle breakdown), including one fatal case with multi-organ failure, has been reported. Not established from the sources reviewed: the reviewed source reports this risk but does not specify a symptom list — seek immediate medical attention for any severe or concerning new symptom, and ask your prescriber what specific warning signs to watch for.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (1)
Sudden onset of sleep during daily activities, including driving, has been reported with carbidopa/levodopa-based regimens including tolcapone, sometimes without warning drowsiness — serious
Symptoms: Sudden onset of sleep during daily activities, including driving, has been reported with carbidopa/levodopa-based regimens including tolcapone, sometimes without warning drowsiness. Discuss driving and operating machinery with your prescriber.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (1)
Interactions
| Medicine or test | Effect | Action |
|---|---|---|
| Non-selective MAO inhibitors | Combining tolcapone with a non-selective MAO inhibitor would inhibit most of the normal catecholamine-metabolism pathways and should be avoided. Selective MAO-B inhibitors (e.g., selegiline) are considered compatible. | (1) |
| Warfarin | Tolcapone has affinity for CYP2C9; your prescriber may want to monitor coagulation status (e.g., INR) more closely if you take warfarin, although an in vivo interaction study with a related CYP2C9 substrate showed no interaction. | (1) |
| Other COMT substrates (e.g., alpha-methyldopa, dobutamine, apomorphine, isoproterenol) | Because tolcapone inhibits the COMT enzyme these drugs also depend on, your prescriber may consider a dose reduction of these medicines. | (1) |
| Levodopa/carbidopa | Tolcapone increases and prolongs levodopa's effect. Average levodopa dose reductions of about 30% are typical when starting tolcapone, and more than 70% of patients taking over 600 mg/day of levodopa needed their prescriber to reduce the levodopa dose. Do not adjust your own levodopa dose — this is managed by your prescriber. | (1) |
Pregnancy, breastfeeding, kidney/liver function, age
Pregnancy
Tolcapone was not teratogenic alone in animal studies, but increased abortion rates were seen in rabbits at high doses, and combined with levodopa/carbidopa, increased fetal malformations (digit defects) were seen in rabbits. Tolcapone should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus — discuss with your doctor. (1)
Breastfeeding
Tolcapone is excreted into milk in animal studies. Tell your doctor if you intend to breastfeed. (1)
Renal_impairment
Renal: no dose adjustment needed for mild-to-moderate impairment; use with caution in severe impairment; safety has not been studied for creatinine clearance below 25 mL/min. Hepatic: contraindicated if there is clinical evidence of active liver disease; in moderate cirrhosis (Child-Pugh Class B), drug clearance is reduced by about half, which can roughly double the average unbound drug concentration — your prescriber will factor this into any decision to use tolcapone at all in liver-impaired patients. (1)
Hepatic_impairment
Renal: no dose adjustment needed for mild-to-moderate impairment; use with caution in severe impairment; safety has not been studied for creatinine clearance below 25 mL/min. Hepatic: contraindicated if there is clinical evidence of active liver disease; in moderate cirrhosis (Child-Pugh Class B), drug clearance is reduced by about half, which can roughly double the average unbound drug concentration — your prescriber will factor this into any decision to use tolcapone at all in liver-impaired patients. (1)
Monitoring
(1)Storage
Follow the exact product label and keep medicines away from children.
Study the drug class: Antiparkinsonian agents
Professional information
Clinician-facing context only. This section does not replace current product labeling.
US
Indication: Adjunct to levodopa/carbidopa for Parkinson's disease with symptom fluctuations
Dose summary: Starting dose 100 mg PO TID, first dose with the first daily levodopa/carbidopa dose, subsequent doses ~6 and 12 hours later. Maximum 200 mg TID only if incremental benefit justifies increased hepatotoxicity risk. Withdraw if no substantial clinical benefit within 3 weeks. Average levodopa dose reduction ~30% (>70% of patients on >600 mg/day levodopa required reduction).
Renal context: No adjustment for mild-to-moderate renal impairment; use with caution in severe impairment; not studied for CrCl <25 mL/min. (1)
Frequently asked questions
What is tolcapone used for?
Tolcapone is used as an add-on to levodopa/carbidopa for Parkinson's disease symptom fluctuations, specifically for patients who have not responded well to, or are not candidates for, other add-on therapies — because of its liver-failure risk, it is not a first-choice add-on treatment.
Why does tolcapone require written consent and regular liver tests?
Tolcapone carries a US FDA boxed warning for potentially fatal acute liver failure. No test can reliably predict who is at risk beforehand, so your prescriber must fully explain the risk and you must provide written acknowledgment before starting, and you need baseline liver blood tests plus tests every 2-4 weeks for the first 6 months (and again for 6 months after any dose increase to 200 mg three times daily).
Can I stop taking tolcapone on my own if I feel fine?
Abrupt withdrawal or dose lowering has been linked to a rare, serious symptom complex resembling neuroleptic malignant syndrome (fever, muscle rigidity, confusion). Any change to your tolcapone treatment is decided and managed by your prescriber.
What are the most common side effects?
The most common effects seen more often than with placebo are dyskinesia (involuntary movements), nausea, diarrhea, and reduced appetite. Diarrhea is the most common reason people stop taking tolcapone.
Is tolcapone safe during pregnancy or breastfeeding?
Tolcapone should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus — animal studies combining it with levodopa/carbidopa showed increased fetal malformations. Tell your doctor if you intend to breastfeed, since tolcapone is excreted into milk in animal studies.
What should I do if I notice yellowing of my skin or eyes, or dark urine?
Contact your healthcare provider immediately — these can be signs of liver injury and should not wait for your next scheduled liver test.
What happens with a tolcapone overdose?
Seek emergency medical attention or contact a poison control center immediately. In a study of supratherapeutic doses combined with levodopa/carbidopa, nausea, vomiting, and dizziness were observed. Treatment is hospitalization and supportive care; hemodialysis is unlikely to help.
Can tolcapone cause sudden sleepiness while driving?
Yes — sudden onset of sleep during daily activities, including driving, has been reported with carbidopa/levodopa-based regimens including tolcapone, sometimes without warning drowsiness. Discuss driving and operating machinery with your prescriber.
What is the mechanism of action of tolcapone?
Tolcapone is a reversible catechol-O-methyltransferase (COMT) inhibitor. Tolcapone is highly protein-bound (>99.9%) but does not displace warfarin, phenytoin, tolbutamide, or digitoxin at therapeutic concentrations, and shows no clinically relevant interaction with CYP 2A6, 1A2, 3A4, 2C19, or 2D6 substrates in vitro or in vivo. (1)
What is the generic name of Tolcapone?
The generic name is tolcapone. It is sold under brand names including Tasmar.
What class of drug is tolcapone?
Tolcapone is classed as: Catechol-O-methyltransferase (COMT) inhibitor.
References
- TASMAR — tolcapone tablet, film coated (prescribing information)U.S. Food and Drug Administration · United States · dated 2025 · accessed 2026-08-06 · source 1
- TOLCAPONE TABLET, FILM COATED [OCEANSIDE PHARMACEUTICALS] — US prescribing information (DailyMed SPL)U.S. National Library of Medicine (DailyMed) · US · accessed 2026-08-14 · source 2
- Tolcapone — patient drug information (MedlinePlus)U.S. National Library of Medicine (MedlinePlus) · US · accessed 2026-08-14 · source 3
- Tasmar — FDA approval record (Drugs@FDA NDA020697)U.S. Food and Drug Administration · US · accessed 2026-08-14 · source 4
- tolcapone — RxNorm normalized drug concept (RXCUI 72937)U.S. National Library of Medicine (RxNorm) · US · accessed 2026-08-14 · source 5
Brand names by country
Single-ingredient tolcapone names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.
Priority countries
United States
- Tasmar100 mg · bausch health us llc