Mefenamic Acid

Indications

Mefenamic Acid is used for: Rheumatoid arthritis, Osteoarthritis, Dysmenorrhoea, Menorrhagia, Dental pain, Pain and inflammation, Mild to moderate pain, Postoperative pain

Adult Dose

Oral Rheumatoid arthritis; Mild to moderate pain; Dental pain; Postoperative pain; Dysmenorrhoea; Osteoarthritis; Menorrhagia Adult: 250-500 mg upto 3 times daily for 3-7 days. Max. 1.5 gm total.

Child Dose

Oral Rheumatoid arthritis; Mild to moderate pain; Dental pain; Postoperative pain; Dysmenorrhoea; Osteoarthritis; Menorrhagia Child: >6 mth 25 mg/kg daily in divided doses for up to 7 days.

Renal Dose

Administration

Should be taken with food.

Contra Indications

Hypersensitivity to mefenamic acid, aspirin or other NSAIDs. Patient w/ inflammatory bowel disease, active ulceration or chronic inflammation of the upper or lower GI tract, renal failure. History of asthma, urticaria, allergic-type reactions. Treatment of perioperative pain in the setting of CABG surgery, pregnancy (3rd trimester), lactation. Coronary artery bypass graft surgery, severe renal impairment, severe heart failure.

Precautions

Patient w/ known CV disease or risk factors for CV disease, history of GI bleeding or peptic ulceration, fluid retention or heart failure. Renal and hepatic impairment. Anemia, bronchospasm, HTN, SLE, fluid retention, bleeding diathesis. Pregnancy and lactation. Patient Counselling May impair ability to drive or operate machinery. Monitoring Parameters Monitor CBC, chemistry profile, hepatic and renal function during long-term therapy. BP should be monitored closely during initiation and throughout therapy. Lactation: contraindicated; excreted in breast milk

Pregnancy-Lactation

Pregnancy Category: C; D if used for prolonged periods, or near term (premature closure of ductus arteriosus) Lactation: contraindicated; excreted in breast milk

Interactions

Concomitant use w/ CYP2C9 isoenzyme inhibitors may alter safety and efficacy of mefenamic acid. May enhance methotrexate toxicity. Reduced BP response to ACE inhibitors or angiotensin II receptor antagonists. Increased risk of serious GI events w/ aspirin. May reduce the natriuretic effects of furosemide or thiazide diuretics. Reduced renal lithium clearance and elevated plasma lithium levels. May enhance anticoagulant effect of warfarin.

Side Effects

Side effects of Mefenamic Acid : >10% Borderline elevations of one or more LFTs (<15%) 1-10% Abdominal pain, Anorexia, Diarrhea, Nausea, Pyrosis, Gastritis, Flatulence, Constipation, Steatorrhea, Upper GI ulcers, gross bleeding/perforation (1% of patients treated for 3-6 mth and 2-4% of those treated for 1 yo) <1% Leukopenia, Eosinophilia, Thrombocytopenic purpura, Agranulocytosis, Pancytopenia, Bone marrow hypoplasia, Renal failure (including papillary necrosis & acute interstitial nephritis), Acute interstitial nephritis has been associated with hematuria, proteinuria, & nephrotic syndrome Potentially Fatal: Autoimmune haemolytic anaemia; convulsions (overdosage).

Mode of Action

Mefenamic acid, an anthranilic acid derivative, is a prototypical NSAID. It reversibly inhibits the cyclooxygenase-1 and -2 (COX-1 and -2) enzymes, thus resulting in reduced synthesis of prostaglandin precursors. It has analgesic and antipyretic properties w/ minor anti-inflammatory activity.