Pharmacokinetics
Absorption: Rapidly absorbed. T max is 2 to 4 h. C max is 20 mcg/mL (single doses). Steady state is reached in 2 days.
Distribution: Apparent Vd is 1.06 L/kg. Protein binding is more than 90%. Excreted in breast milk.
Metabolism: Metabolized by CYP-450 enzyme CYP2C9 to 3-hydroxymethyl mefenamic acid (metabolite I). Further oxidation to a 3-carboxymefenamic acid (metabolite II) may occur. The metabolites may undergo glucuronidation, and mefenamic acid is also glucuronidated directly.
Elimination: Approximately 52% of a dose is excreted into the urine primarily as glucuronides of mefenamic acid (6%), 3-hydroxymefenamic acid (25%), and 3-carboxymefenamic acid (21%). The fecal route of elimination accounts for up to 20% of the dose, mainly in the form of unconjugated 3-carboxymefenamic acid. The half-life is approximately 2 h.
Read more about this topic: Mefenamic Acid