♦ Entacapone is a reversible, specific and mainly peripherally acting catechol-O-methyl transferase (COMT) inhibitor (see 58).
♦ It decreases the metabolic loss of dopamine to 3 O-methyl dopa.
♦ It increases the half-life of levodopa by 30-50% so that the levodopa total daily dose may be reduced with no significant effect on the Cmax (peak concentration) or Tmax (time to Cmax).
♦ It is particularly indicated for patients experiencing end-of-dose 'wearing off, but can also be useful in patients with nonfluctuating disease.
♦ A single dose of 200 mg should be given together with each dose of levodopa up to ten times daily (up to eight times daily recommended in the USA).
♦ There is a small risk of developing diarrhoea after approximately 1 month of drug initiation, often requiring drug discontinuation. Entacapone should not be cut in half or chewed as it can discolour teeth yellow-orange. Warn patients also of benign orange discoloration of urine.
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