Tolcapone (2 brand names, 1 dosage form, 1 route)
Available dosage forms: TABLET.
Routes of administration: ORAL.
Brand Names
- TASMAR
- TOLCAPONE
Boxed Warning
Because of the risk of potentially fatal, acute fulminant liver failure, Tolcapone tablets should ordinarily be used in patients with Parkinson’s disease on l-dopa/carbidopa who are experiencing symptom fluctuations and are not responding satisfactorily to or are not appropriate candidates for other adjunctive therapies (see INDICATIONS and DOSAGE AND ADMINISTRATION sections). Because of the risk of liver injury and because Tolcapone tablets, when it is effective, provides an observable symptomatic benefit, the patient who fails to show substantial clinical benefit within 3 weeks of initiation of treatment, should be withdrawn from Tolcapone tablets. Tolcapone tablets therapy should not be initiated if the patient exhibits clinical evidence of liver disease or two SGPT/ALT or SGOT/AST values greater than the upper limit of normal. Patients with severe dyskinesia or dystonia should be treated with caution (see PRECAUTIONS: Rhabdomyolysis).
Indications and Usage
Tolcapone tablets is indicated as an adjunct to levodopa and carbidopa for the treatment of the signs and symptoms of idiopathic Parkinson’s disease. Because of the risk of potentially fatal, acute fulminant liver failure, Tolcapone tablets should ordinarily be used in patients with Parkinson’s disease on l-dopa/carbidopa who are experiencing symptom fluctuations and are not responding satisfactorily to or are not appropriate candidates for other adjunctive therapies. Because of the risk of liver injury and because Tolcapone tablets, when it is effective, provides an observable symptomatic benefit, the patient who fails to show substantial clinical benefit within 3 weeks of initiation of treatment, should be withdrawn from Tolcapone tablets. The effectiveness of Tolcapone tablets was demonstrated in randomized controlled trials in patients receiving concomitant levodopa therapy with carbidopa or another aromatic amino acid decarboxylase inhibitor who experienced end of dose wearing-off phenomena as well as in patients who did not experience such phenomena (see CLINICAL PHARMACOLOGY: Clinical Studies ).
Dosage and Administration
Because of the risk of potentially fatal, acute fulminant liver failure, Tolcapone tablets should ordinarily be used in patients with Parkinson’s disease on l-dopa/carbidopa who are experiencing symptom fluctuations and are not responding satisfactorily to or are not appropriate candidates for other adjunctive therapies (see INDICATIONS and DOSAGE AND ADMINISTRATION sections). BECAUSE OF THE RISK OF LIVER INJURY AND BECAUSE TOLCAPONE TABLETS WHEN IT IS EFFECTIVE PROVIDES AN OBSERVABLE SYMPTOMATIC BENEFIT, THE PATIENT WHO FAILS TO SHOW SUBSTANTIAL CLINICAL BENEFIT WITHIN 3 WEEKS OF INITIATION OF TREATMENT, SHOULD BE WITHDRAWN FROM TOLCAPONE TABLETS. Tolcapone tablets therapy should not be initiated if the patient exhibits clinical evidence of liver disease or two SGPT/ALT or SGOT/AST values greater than the upper limit of normal. Patients with severe dyskinesia or dystonia should be treated with caution (see PRECAUTIONS: Rhabdomyolysis). Patients who develop evidence of hepatocellular injury while on Tolcapone tablets and are withdrawn from the drug for any reason may be at increased risk for liver injury if Tolcapone tablets is reintroduced. These patients should not ordinarily be considered for retreatment with Tolcapone tablets. Only prescribe Tolcapone tablets for patients taking concomitant carbidopa levodopa therapy. The initial dose of Tolcapone tablets is always 100 mg three times per day. The recommended daily dose of Tolcapone tablets is also 100 mg tid. In clinical trials, elevations in ALT occurred more frequently at the dose of 200 mg tid. While it is unknown whether the risk of acute fulminant liver failure is increased at the 200-mg dose, it would be prudent to use 200 mg only if the anticipated incremental clinical benefit is justified (see BOXED WARNING, WARNINGS, and PRECAUTIONS: Laboratory Tests ). If a patient fails to show the expected incremental benefit on the 200-mg dose after a total of 3 weeks of treatment (regardless of dose), Tolcapone tab
Contraindications
Tolcapone tablets are contraindicated in patients with liver disease, in patients who were withdrawn from Tolcapone tablets because of evidence of Tolcapone tablets-induced hepatocellular injury or who have demonstrated hypersensitivity to the drug or its ingredients. Tolcapone tablets is also contraindicated in patients with a history of nontraumatic rhabdomyolysis or hyperpyrexia and confusion possibly related to medication (see PRECAUTIONS: Events Reported With Dopaminergic Therapy ).
Adverse Reactions
Cases of severe hepatocellular injury, including fulminant liver failure resulting in death, have been reported in postmarketing use. As of May 2005, three cases of fatal fulminant hepatic failure have been reported from more than 40,000 patient years of worldwide use. This incidence may be 10- to 100-fold higher than the background incidence in the general population. All three cases were reported within the first six months of initiation of treatment with Tolcapone tablets. Analysis of the laboratory monitoring data in over 3,400 Tolcapone tablets-treated patients participating in clinical trials indicated that increases in SGPT/ALT or SGOT/AST, when present, generally occurred within the first 6 months of treatment with Tolcapone tablets. The imprecision of the estimated increase is due to uncertainties about the base rate and the actual number of cases occurring in association with Tolcapone tablets. The incidence of idiopathic potentially fatal fulminant hepatic failure (i.e., not due to viral hepatitis or alcohol) is low. One estimate, based upon transplant registry data, is approximately 3/1,000,000 patients per year in the United States. Whether this estimate is an appropriate basis for estimating the increased risk of liver failure among Tolcapone tablets users is uncertain. Tolcapone tablets users, for example, differ in age and general health status from candidates for liver transplantation. Similarly, underreporting of cases may lead to significant underestimation of the increased risk associated with the use of Tolcapone tablets. During the premarketing development of tolcapone, two distinct patient populations were studied, patients with end-of-dose wearing-off phenomena and patients with stable responses to levodopa therapy. All patients received concomitant treatment with levodopa preparations, however, and were similar in other clinical aspects. Adverse reactions are shown for these two populations combined. The most commonly observed adverse reacti
Drug Interactions
See PRECAUTIONS: Drug Interactions .
Mechanism of Action
Tolcapone is a selective and reversible inhibitor of catechol-O-methyltransferase (COMT). In mammals, COMT is distributed throughout various organs. The highest activities are 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, 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 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. 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. Tolcapone enters the CNS to a minimal extent, but has been shown to inhibit central COMT activity in animals.
Overdosage
The highest dose of tolcapone administered to humans was 800 mg tid, with and without levodopa/carbidopa co-administration. This was in a 1-week study in elderly, healthy volunteers. The peak plasma concentrations of tolcapone at this dose were on average 30 mcg/mL (compared to 3 mcg/mL and 6 mcg/mL with 100 mg and 200 mg tolcapone, respectively). Nausea, vomiting and dizziness were observed, particularly in combination with levodopa/carbidopa. The threshold for the lethal plasma concentration for tolcapone based on animal data is >100 mcg/mL. Respiratory difficulties were observed in rats at high oral (gavage) and intravenous doses and in dogs with rapidly injected intravenous doses.