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Tasmar: Full Drug Profile

Medically reviewed by Min Clinic Staff | Updated: January 2026

Tasmar - General Information

Tasmar is a drug that inhibits the enzyme catechol-O-methyl transferase (COMT). It is used in the treatment of Parkinson's disease as an adjunct to levodopa/carbidopa medication. It is a yellow, odorless, non-hygroscopic, crystalline compound. [Wikipedia]

 

Pharmacology of Tasmar

Tasmar is a selective and reversible inhibitor of catechol-O-methyltransferase (COMT). In humans, COMT is distributed throughout various organs. 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, 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. When tolcapone is given in conjunction with levodopa and an aromatic amino acid decarboxylase inhibitor, such as carbidopa, plasma levels of levodopa are more sustained than after administration of levodopa and an aromatic amino acid decarboxylase inhibitor alone. It is believed that these 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 in patients as well as increased levodopa adverse effects, sometimes requiring a decrease in the dose of levodopa.

 

Tasmar for patients

Tolcapone, an inhibitor of catechol-O-methyltransferase (COMT), is used in the treatment of Parkinson's disease as an adjunct to levodopa/carbidopa therapy.

Tolcapone, should not be used by patients until there has been a complete discussion of the risks and the patient has provided written informed consent.

Patients should know about clinical signs and symptoms that suggest the onset of hepatic injury (persistent nausea, fatigue, lethargy, anorexia, jaundice, dark urine, pruritus, and right upper quadrant tenderness)

Patients should know about the risk of hepatic failure while using Tolcapone.

There is a need to have regular blood tests to monitor liver enzymes for the patients.

Because of the possible additive sedative effects, caution should be used when patients are taking other CNS depressants in combination with Tolcapone.

 

Tasmar Interactions

Protein Binding: Although tolcapone is highly protein bound, in vitro studies have shown that tolcapone at a concentration of 50 mg/mL did not displace other highly protein-bound drugs from their binding sites at therapeutic concentrations. The experiments included warfarin (0.5 to 7.2 pg/mL), phenytoin (4.0 to 38.7 mg/mL), tolbutamide (24.5 to 961 mg/mL) and digitoxin (9.0 to 27.0 mg/mL).

Drugs Metabolized by Catechol-O-Methyl transferase (COMT): Tolcapone may influence the pharmacokinetics of drugs metabolized by COMT However, no effects were seen on the pharmacokinetics of the COMT substrate carbidopa. The effect of tolcapone on the pharmacokinetics of other drugs of this class such as a-methyldopa, dobutamine, apomorphine, and isoproterenol has not been evaluated. A dose reduction of such compounds should be considered when they are coadministered with tolcapone.

Effect of Tolcapone on the Metabolism of Other Drugs: In vitro experiments have been performed to assess the potential of tolcapone to interact with isoenzymes of cytochrome P450 (CYP). No relevant interactions with substrates for CYP 2A6 (coumadin), CYP 1A2 (caffeine), CYP 3A4 (midazolam, terfenadine, cyclosporine), CYP 2C19 (S- mephenytoin) and CYP 206 (desipramine) were observed in vitro. The absence of an interaction with desipramine, a drug metabolized by cytochrome P450 2D6, was also confirmed in an in vivo study where tolcapone did not change the pharmacokinetics of desipramine.

Due to its affinity to cytochrome P450 2C9 in vitro, tolcapone may interfere with drugs, whose clearance is dependent on this metabolic pathway, such as tolbutamide and warfarin. However, in an in vivo interaction study, tolcapone did not change the pharmacokinetics of tolbutamide. Therefore, clinically relevant interactions involving cytochrome P450 2C9 appear unlikely. Similarly, tolcapone did not affect the pharmacokinetics of desipramine, a drug metabolized by cytochrome P450 206, indicating that interactions with drugs metabolized by that enzyme are unlikely. Since clinical information is limited regarding the combination of warfarin and tolcapone, coagulation parameters should be monitored when these two drugs are coadministered.

Drugs That Increase Catecholamines: Tolcapone did not influence the effect of ephedrine, an indirect sympathomimetic, on hemodynamic parameters or plasma catecholamine levels, either at rest or during exercise. Since tolcapone did not alter the tolerability of ephedrine, these drugs can be coadministered.

When TASMAR was given together with levodopa/carbidopa and desipramine, there was no significant change in blood pressure, pulse rate and plasma concentrations of desipramine. Overall, the frequency of adverse events increased slightly. These adverse events were predictable based on the known adverse reactions to each of the three drugs individually. Therefore, caution should be exercised when desipramine is administered to Parkinsonís disease patients being treated with TASMAR and levodopa/carbidopa.

In clinical trials, patients receiving TASMAR/levodopa preparations reported a similar adverse event profile independent of whether or not they were also concomitantly administered selegiline (a selective MAO-B inhibitor).

 

Tasmar Contraindications

TASMAR tablets are contraindicated in patients with liver disease, in patients who were withdrawn from TASMAR because of evidence of TASMAR-induced hepatocellular injury or who have demonstrated hypersensitivity to the drug or its ingredients.

TASMAR is also contraindicated in patients with a history of non-traumatic rhabdomyolysis or hyperpyrexia and confusion possibly related to medication.

 

Additional information about Tasmar

Tasmar Indication: For the treatment of Parkinson's Disease Mechanism Of Action: The precise mechanism of action of tolcapone is unknown, but it is believed to be related to its ability to inhibit COMT and alter the plasma pharmacokinetics of levodopa. Drug Interactions: Not Available Food Interactions: Not Available Generic Name: Tolcapone Synonyms: Not Available Drug Category: Antiparkinson Agents; Antidyskinetics; Central Nervous System Agents; Enzyme Inhibitors Drug Type: Small Molecule; Approved; Withdrawn Other Brand Names containing Tolcapone: Tasmar; Absorption: Rapidly absorbed (absolute bioavailability is about 65%) Toxicity (Overdose): LD50 = 1600 mg/kg (Orally in rats) Protein Binding: > 99.9% (to serum albumin) Biotransformation: The main metabolic pathway of tolcapone is glucuronidation Half Life: 2-3.5 hours Dosage Forms of Tasmar: Tablet, film coated Oral Chemical IUPAC Name: (3,4-dihydroxy-5-nitrophenyl)-(4-methylphenyl)methanone Chemical Formula: C14H11NO5 Tolcapone on Wikipedia: https://en.wikipedia.org/wiki/Tolcapone Organisms Affected: Humans and other mammals