Entacapone

Entacapone is a reversible, specific and mainly peripherally-acting COMT inhibitor and decreases the metabolic loss of levodopa to 3-O-methyldopa. Therefore, entacapone increases the amount of levodopa available to the brain. entacapone is effective for increasing ‘on’ time in patients who are experiencing motor fluctuations on levodopa therapy.

Indications

As an adjunct to standard preparations of levodopa/benserazide or levodopa/carbidopa for use in patients with Parkinson’s disease and end-of-dose motor fluctuations, who cannot be stabilised on those combinations.

Dosage

Oral; One 200 mg tablet taken with each levodopa/dopa-decarboxylase inhibitor dose. The maximum recommended dose is 2,000 mg daily

Contra-Indications

Hypersensitivity, liver impairment; pheochromocytoma; history of Neuroleptic Malignant Syndrome and/or non-traumatic rhabdomyolysis; concomitant use with non-selective monoamine oxidase (MAO-A and MAO-B) inhibitors (e.g. phenelzine, tranylcypromine).

Special Precautions

Pregnancy : category C; Use if risk to fetus outweighs benefits. Lactation : entacapone is excreted in milk Elderly : No dose adjustment is required

Side Effects

dyskinesia , nausea , dizziness , insomnia , hallucinations, dystonia, Gastrointestinal effects, such as diarrhoea , abdominal pain, dry mouth, constipation, reddish-brown discolouration of the urine. The most common reason for discontinuation of drug is dyskinesia and diarrhoea.

Drug Interactions

Increased risk of postural hypotension when used concurrently with hypotensive drugs. Severe orthostatic hypotension may result from concurrent usage with MAOIs. Dopamine D2 receptor antagonists, phenytoin or papaverine may reduce the efficacy of levodopa. Iron salts may reduce the bioavailability. Concurrent usage with drugs that interfere with biliary excretion may lead to increased plasma levels of entacapone. May depress prolactin secretion and increase growth hormone levels.