Ponstan Mechanism of Action

Pharmacology: Pharmacodynamics: Mechanism of Action: Mefenamic acid is a nonsteroidal agent with demonstrated anti-inflammatory, analgesic, and antipyretic activity in laboratory animals. Mefenamic acid was found to inhibit prostaglandin synthesis and to compete for binding at the prostaglandin receptor sites in animal models.
Pharmacokinetics: Absorption: Mefenamic acid is rapidly absorbed from the gastrointestinal tract. Following administration of a one gram oral dose to adults, peak plasma levels of 10 μg/mL occur in 1 to 4 hours, with a half-life of 2 hours. Plasma levels are proportional to dose, following multiple doses, with no drug accumulation. One gram of mefenamic acid administered four times daily produces peak blood levels of 20 μg/mL by the second day of administration.
Distribution: Mefenamic acid is extensively bound to plasma proteins.
Metabolism: Mefenamic acid metabolism is predominantly mediated via cytochrome P450 (CYP) 2C9 in the liver. Patients who are known or suspected to be poor CYP 2C9 metabolizers based on previous history/experience with other CYP 2C9 substrates should be administered mefenamic acid with caution as they may have abnormally high plasma levels due to reduced metabolic clearance.
Elimination: Following a single oral dose, 52% to 67% of the dose was recovered from the urine as unchanged drug or one of two metabolites. Assay of stools over 3 days accounted for 20% to 25% of the dose, chiefly as unconjugated metabolite II.
Toxicology: Preclinical safety data: Rats given up to 10 times the human dose showed decreased fertility, delay in parturition, and a decreased rate of survival to weaning. No fetal abnormalities were observed in this study and in another study in dogs receiving 10 times the human dose.