Tolcapone, sold under the brand name Tasmar, is a medication used to treat Parkinson's disease (PD). It is a selective, potent and reversible nitrocatechol-type inhibitor of the enzyme catechol-O-methyltransferase (COMT). It has demonstrated significant l + some more technical info; clinically it is used as an adjunct to levodopa therapy to reduce motor fluctuations by inhibiting peripheral and central methylation of levodopa and endogenous catecholamines. Tolcapone is orally administered, crosses the blood brain barrier, is highly protein bound, and is primarily metabolized in the liver to conjugated metabolites; its plasma half-life is relatively short while COMT inhibition can persist beyond plasma exposure, which supports dosing with each levodopa administration in patients requiring prolonged dopaminergic effect.
Parent: Tolcapone
Parent: Tolcapone
Typical pharmaceutical quality-control limits for tolcapone active pharmaceutical ingredient set stringent levels for related substances and impurities to ensure safety and efficacy; common industry example limits are individual known related compounds controlled to about 0.05 to 0.10 percent by weight, unspecified individual impurities controlled to about 0.10 to 0.20 percent, and total impurities limited to about 0.5 to 1.0 percent, with reporting and identification thresholds aligned to ICH guidance and adjusted based on compound daily dose and toxicological qualification. Relevant related compounds observed in synthesis and stability studies include positional nitrocatechol isomers, reduced nitro species, minor oxidation products and process-related intermediates; manufacturers routinely monitor these by validated HPLC or LC-MS methods and set acceptance criteria and qualification plans per regulatory expectations.
Tolcapone is used as an adjunctive treatment in Parkinsons disease to extend the clinical benefit of levodopa by inhibiting COMT, thereby reducing off time and smoothing motor fluctuations in patients receiving levodopa/carbidopa.
Tolcapone has been associated with hepatotoxicity in some patients and requires baseline and periodic liver function monitoring during treatment; use is contraindicated in patients with acute or chronic liver disease and therapy should be discontinued if clinically significant liver enzyme elevations or signs of liver injury occur.
Both entacapone and tolcapone inhibit COMT and are used to augment levodopa, but tolcapone inhibits both peripheral and central COMT and has a longer duration of COMT inhibition, while entacapone is primarily a peripheral COMT inhibitor with a more favorable hepatic safety profile; dosing, monitoring requirements and risk profiles differ and choice between them is based on clinical benefit, tolerability and safety considerations.
