Mefenamic acid

Generic Medicine Info
Indications and Dosage
Dental pain, Headache, Menorrhagia, Mild to moderate pain, Osteoarthritis, Pain and inflammation associated with musculoskeletal and joint disorders, Postoperative pain, Primary dysmenorrhoea, Rheumatoid arthritis
Adult: 500 mg tid.
Child: ≥14 years Same as adult dose.
Elderly: Initiate at a lower dose and shortest possible duration.
Renal Impairment
Severe: Contraindicated.
Hepatic Impairment
Severe: Contraindicated.
Should be taken with food.
Hypersensitivity. Patients with active or history of recurrent peptic ulcer/haemorrhage, history of gastrointestinal bleeding or perforation (related to previous NSAID therapy), inflammatory bowel disease, severe heart failure, history of asthma, bronchospasm, rhinitis, angioedema, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs. Treatment of peri-operative pain in the setting of CABG surgery. Renal (CrCl <30 mL/min) and severe hepatic impairment. Pregnancy (3rd trimester).
Special Precautions
Patient with risk factors for CV events (e.g. hypertension, hyperlipidaemia, diabetes mellitus, smoking), mild to moderate heart failure, hypovolaemia, dehydration. Debilitated patient. Renal and hepatic impairment. Elderly. Pregnancy (1st-2nd trimester) and lactation.
Adverse Reactions
Significant: Anaphylactoid reactions, fluid retention, anaemia, hyperkalaemia.
Blood and lymphatic system disorders: Eosinophilia, leukopenia, thrombocytopenia, purpura, agranulocytosis.
Cardiac disorders: Dyspnoea.
Ear and labyrinth disorders: Tinnitus.
Gastrointestinal disorders: Diarrhoea, nausea, vomiting, abdominal pain, flatulence, constipation, dyspepsia, heartburn, gastritis.
Hepatobiliary disorders: Hepatitis, jaundice.
Investigations: Increased liver enzymes.
Nervous system disorders: Aseptic meningitis, headache.
Psychiatric disorders: Nervousness, insomnia, confusion, depression.
Renal and urinary disorders: Dysuria, cystitis.
Reproductive system and breast disorders: Haematuria.
Respiratory, thoracic and mediastinal disorders: Asthma.
Skin and subcutaneous tissue disorders: Pruritus, urticaria, rash, erythema multiforme.
Vascular disorders: Hypertension.
Potentially Fatal: CV thrombotic events including MI and stroke, gastrointestinal inflammation, bleeding, ulceration, perforation. Rarely, exfoliative dermatitis, toxic epidermal necrolysis, Stevens-Johnson syndrome, fulminant hepatitis, liver necrosis, hepatic failure.
PO: C, Z (NSAIDs caused foetal ductus arteriosus premature closure, foetal renal impairment and persistent pulmonary hypertension. Avoid near term, else use lowest dose for shortest time.)
Patient Counseling Information
This drug may cause dizziness, drowsiness, and visual disturbances, if affected, do not drive or operate machinery.
Monitoring Parameters
Monitor CBC, chemistry profile, occult blood loss, renal and liver function. Blood pressure should be monitored during initiation of treatment and throughout the course of therapy.
Symptoms: Lethargy, drowsiness, headache, nausea, vomiting, epigastric pain, gastrointestinal bleeding. Rarely, diarrhoea, disorientation, excitation, tinnitus, fainting, hypertension, acute renal failure, respiratory depression, and coma. Management: Symptomatic and supportive treatment. Administer activated charcoal or consider emesis within 4 hours of ingestion of large overdoses.
Drug Interactions
May increase the risk of bleeding with other NSAIDs or salicylates (e.g. aspirin), anticoagulants (e.g. warfarin), corticosteroids, SSRI. Increased the risk of nephrotoxicity of ciclosporin or tacrolimus. May decrease efficacy of antihypertensive agents (e.g. ACE inhibitors, angiotensin II antagonists, ß-blockers). Decreased natriuretic effect of diuretics (e.g. furosemide, hydrochlorothiazide). Increased plasma levels and reduced renal clearance of lithium. Increased serum concentration of digoxin and methotrexate.
Lab Interference
May result to false positive urinary bilirubin in diazo tablet test.
Description: Mefenamic acid, an anthranilic acid derivative, is an NSAID. It reversibly inhibits cyclooxygenase-1 and -2 (COX-1 and -2), thus resulting in reduced rate of prostaglandin synthesis. It exhibits analgesic, anti-inflammatory and antipyretic properties.
Absorption: Rapidly absorbed from the gastrointestinal tract. Time to peak plasma concentration: 2-4 hours.
Distribution: Present in breast milk. Volume of distribution: 1.06 L/kg. Plasma protein binding: >90% to albumin.
Metabolism: Metabolised in the liver by CYP2C9 isoenzyme to 3-hydroxymethyl mefenamic acid, which may then be oxidised to 3-carboxymefenamic acid.
Excretion: Via urine (approx 52%; 6% as glucuronides, 25% as 3-hydroxymefenamic acid, 21% as 3-carboxymefenamic acid), faeces (up to 20%, mainly as unconjugated 3-carboxymefenamic acid). Elimination half-life: Approx 2 hours.
Chemical Structure

Chemical Structure Image
Mefenamic acid

Source: National Center for Biotechnology Information. PubChem Database. Mefenamic acid, CID=4044, (accessed on Jan. 22, 2020)

Store below 30°C.
MIMS Class
Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)
ATC Classification
M01AG01 - mefenamic acid ; Belongs to the class of non-steroidal antiinflammatory and antirheumatic products, fenamates.
Anon. Mefenamic Acid. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. Accessed 28/07/2014.

Buckingham R (ed). Mefenamic Acid. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. Accessed 11/04/2019.

Joint Formulary Committee. Mefenamic Acid. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. Accessed 07/05/2019.

McEvoy GK, Snow EK, Miller J et al (eds). Mefenamic Acid. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). Accessed 28/07/2014.

Mefenamic Acid Capsule (Breckenridge Pharmaceutical, Inc.). DailyMed. Source: U.S. National Library of Medicine. Accessed 11/04/2019.

Pfizer New Zealand Ltd. Ponstan Capsules data sheet 29 November 2018. Medsafe. Accessed 11/04/2019.

Disclaimer: This information is independently developed by MIMS based on Mefenamic acid from various references and is provided for your reference only. Therapeutic uses, prescribing information and product availability may vary between countries. Please refer to MIMS Product Monographs for specific and locally approved prescribing information. Although great effort has been made to ensure content accuracy, MIMS shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2022 MIMS. All rights reserved. Powered by
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