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Pharmacology: Pharmacodynamics: Decreases synthesis of prostaglandins due to selective inhibition of cyclooxygenase-2 (COX-2) enzyme; has antipyretic, analgesic, and anti-inflammatory properties. Etoricoxib does not inhibit cyclooxygenase-1 (COX-1) at therapeutic concentrations.
Pharmacokinetics: Etoricoxib is well absorbed from the gastrointestinal tract after oral doses. Peak plasma concentrations occur in about 1 hour in fasted adults; food delays absorption by about 2 hours, although it has no effect on the extent of absorption. Plasma protein binding is about 92%. At steady state the half-life of etoricoxib is about 22 hours. Etoricoxib is extensively metabolised with less than 2% of a dose recovered in the urine as the parent drug. The major route of metabolism is via cytochrome P450 isoenzymes including CYP3A4 to form the 6'-hydroxymethyl derivative of etoricoxib, which is then oxidised to the 6'-carboxylic acid derivative, the major metabolite. Both are inactive or only weak cyclo-oxygenase-2 (COX-2) inhibitors. Excretion is mainly via the urine (70%) with only 20% of a dose appearing in the faeces. Studies in animals suggest that etoricoxib may cross the placenta and that some is distributed into breast milk.
