Entacapone

Entacapone (INN) is a drug that functions as a catechol-O-methyl transferase (COMT) inhibitor. It is used in the treatment of Parkinson's disease.

When administered in conjunction with dopaminergic agents such as L-DOPA, entacapone prevents COMT from metabolizing L-DOPA into 3-methoxy-4-hydroxy-L-phenylalanine (3-OMD) in the periphery, which does not easily cross the blood brain barrier (BBB). Pharmacologically, entacapone is somewhat similar to carbidopa or benserazide, in that it is an inhibitor of an enzyme that converts L-DOPA into a compound that cannot cross the blood brain barrier. Carbidopa and benserazide inhibit aromatic L-amino acid decarboxylase, which converts L-DOPA into dopamine, which cannot cross the blood brain barrier.

Entacapone is a member of the class of drugs known as nitrocatechols.

The most frequent undesirable effects caused by entacapone relate to the increased effects of L-DOPA, such as involuntary movements (dyskinesias). These occur most frequently at the beginning of entacapone treatment. Others common side effects are gastrointestinal problems, including diarrhoea, nausea and abdominal pains. The substance may cause urine to turn reddish-brown. This is a harmless side effect and is not a cause for concern. In studies with entacapone, some people have reported experiencing a dry mouth.

Products
Entacapone is developed by Orion Pharma and marketed by Novartis under the trade name COMTan in the United States.

Stalevo is another Novartis medication that contains entacapone in combination with carbidopa and levodopa (active ingredients in Sinemet).