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Mefenamic acid is a non-steroidal
anti-inflammatory drug (NSAID).
Mefenamic acid is a
non-steroidal anti-inflammatory drug (NSAID). It may block certain substances
in the body that are linked to inflammation. NSAIDs treat the symptoms of pain
and inflammation, menstrual pain and may be used for short term (not more than
7 days) for treating mild to moderate pain surgery.
Pharmacological class: NSAID
Mefenamic acid acts
by inhibiting the prostaglandin synthetase, that is, cyclooxygenase enzymes
(COX-1 and COX-2). Hence, it prevents the release of the inflammatory
mediators. As these prostaglandin receptors have a role as a major mediator of
inflammation and/or a role for prostanoid signaling in activity-dependent
plasticity, the symptoms of pain are temporarily reduced.
Pain: 500 mg orally followed by 250 mg every 6 hours as
needed, not to exceed 7 days
Dysmenorrhea: 500 mg orally followed by 250 mg every 6 hours
starting with the onset of menses
Pediatric Dose for Pain: 14 to 18 years: 500 mg orally
followed by 250 mg every 6 hours as needed, not to exceed 7 days
Mefenamic Acid is
rapidly absorbed after oral administration. It has been reported that mefenamic
acid as binds greater than 90% to the albumin. The apparent volume of
distribution estimated following a 500-mg oral dose of mefenamic Acid is 1.06
L/kg. Mefenamic Acid is metabolized by cytochrome P450 enzyme CYP2C9 to
3-hydroxymethyl mefenamic acid (Metabolite I). Mefenamic Acid gets
glucuronidated directly. Approximately 52% of mefenamic acid 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.
Common (affecting between 1 in 10 to 1 in 100):
Uncommon (affecting 1 in 100 to 1 in 1000):
Very rare (affecting
less than 1 in 10,000):
In a recent study,
thirty-five patients (16--23 years old) who had severe primary dysmenorrhea
were treated with 500 mg of mefenamic acid every eight hours for a maximum of
three days during menstruation for three consecutive cycles. A total of 194
treated cycles were evaluated, 110 cycles with mefenamic acid and 84 with
placebo. Mefenamic acid produced complete relief of all the symptoms of
dysmenorrhea in 31 (88.6%) patients in all 98 treated cycles and, in another
two patients, moderate relief in five of the six cycles. It is concluded that
mefenamic acid is safe and effective in most of patients with primary
dysmenorrhea and represents a rational short-term therapy for this syndrome.1
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