Each tablet contains: Mefenamic acid 500mg.
Pharmacology: Pharmacodynamics: Mode or Mechanisms of Action: Mefenamic acid is an analgesic with anti-inflammatory properties, and a demonstrable antipyretic effect.
Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit the activity of the enzyme cyclo-oxygenase, resulting in decreased formation of precursors of prostaglandins and thromboxanes from arachidonic acid. Although the resultant decrease in prostaglandin synthesis and activity in various tissues may be responsible for many of the therapeutic (and adverse) effects of NSAIDs, other actions may also contribute significantly to the therapeutic effects of these medications.
Analgesic: May block pain impulse generation via a peripheral action that may involve reduction of the activity of prostaglandins, and possibly inhibition of the synthesis or actions of other substances that sensitise pain receptors to mechanical or chemical stimulation.
Antidysmenorrheal: By inhibiting the synthesis and activity of intrauterine prostaglandins (which are thought to be responsible for the pain and other symptoms of primary dysmenorrhea), NSAIDs decrease uterine contractility and uterine pressure, increase uterine perfusion, and relieve ischemic as well as spasmodic pain. Also, NSAIDs may relieve to some extent extrauterine symptoms (such as headache, nausea, and vomiting) that may be associated with excessive prostaglandin production.
Vascular headache prophylactic and suppressant: Analgesic actions may be involved in relief of headache. Also, by reducing prostaglandin activity, NSAIDs may directly prevent or relieve certain types of headache thought to be caused by prostaglandin-induced dilation or constriction of cerebral blood vessels.
Pharmacokinetics: Mefenamic acid is well absorbed after oral administration with peak plasma concentration occurring at 2 - 4 hours. The plasma half-life is around 3 hours. Mefenamic acid is extensively bound to plasma proteins (99%). Over 50% of a dose may be recovered in the urine, as unchanged drug or conjugated metabolites.
Mild to moderate pain including muscular, traumatic and dental pain, headaches of most aetiology, postoperative and postpartum pain, pyrexia in children. Dysmenorrhea.
Mild to moderate pain in rheumatoid arthritis (including Still's Disease) and osteoarthrosis.
Menorrhagia due to dysfunctional causes and presence of an IUD when other pelvic pathology has been ruled out.
Usual adult dose: Analgesic or Antidysmenorrheal: 500 mg, 3 times a day initially, followed by 250 mg every six hours as needed.
Note: It is recommended that mefenamic acid be used for no longer than 7 days at a time.
Usual pediatric dose: Children up to 14 years of age: Safety and efficacy have not been established.
Additional dosing information: It is recommended that mefenamic acid therapy be discontinued promptly if diarrhea or a skin rash develops. Patients who develop diarrhea during mefenamic acid therapy are usually unable to tolerate the drug there after.
Symptoms: Large doses produce excitement, incoordination, depression and convulsions in mice. Coma has also been reported.
Treatment: If ingestion is recent, forced emesis or gastric lavage should be performed and activated charcoal then given (0.5g/kg) which may considerably reduce absorption. Careful observation during the first few hours is recommended, as convulsions are most likely to occur during this period. Very high serum levels may be associated with repeated convulsions, which have been successfully suppressed with intravenous diazepam.
Inflammatory bowel disease.
Peptic and/or intestinal ulceration.
Renal and hepatic impairment.
RISK OF GI ULCERATIONS, BLEEDING AND PERFORATION WITH NSAID: Serious GI toxicity, such as bleeding, ulceration and perforation can occur at any time, with or without warning symptoms, in patients treated with NSAID therapy. Although minor upper GI problems (e.g., dyspepsia) are common, usually developing early in therapy, prescribers should remain alert for ulceration and bleeding in patients treated with NSAIDs even in the absence of previous GI tract symptoms.
Studies to date have not identified any subset of patients not at risk of developing peptic ulceration and bleeding. Patients with prior history of serious adverse events and other risk factors associated with peptic ulcer disease (e.g., alcoholism, smoking, and corticosteroid therapy) are at increased risk. Elderly or debilitated patients seem to tolerate ulceration or bleeding less well than other individuals and account for most spontaneous reports for fatal GI events.
In patients suffering from dehydration and renal disease, particularly the elderly, concurrent therapy with other plasma protein binding drugs may necessitate a modification in dosage.
Use in Pregnancy: The safety of mefenamic acid in pregnancy has not been established.
Use in Lactation: Very small amounts enter breast milk and may be transmitted to infants of nursing mothers.
Use in Elderly: Both renal and haematological adverse effects appear to be more prevalent in the elderly. The minimum effective dose should be used and treatment stopped in the presence of diarrhoea or dehydration.
Pregnant women: The safety of mefenamic acid in pregnancy has not been established.
Breast milk: Very small amounts enter breast milk and may be transmitted to infants of nursing mothers.
The commonest adverse effects occurring with mefenamic acid are gastro-intestinal disturbances including diarrhoea. Peptic ulceration and gastro-intestinal bleeding have also been reported. Headache, drowsiness and dizziness have been reported. There may be hypersensitivity reactions including skin rashes and urticaria, and occasionally allergic glomerulonephritis; asthma may be precipitated. Reported haematological effects include haemolytic anaemia, agranulocytosis, pancytopenia and thrombocytopenia. Renal failure, glomerulonephritis and papillary necrosis have been reported.
Therapy should be discontinued if diarrhoea or skin rash occur.
Bronchospasm may be precipitated in patients suffering from, or with a previous history of, bronchial asthma or allergic disease.
Slight potentiation of oral anticoagulants is well documented, but this is rarely significant. When the drug is administered to patients receiving oral anticoagulant drugs, monitoring of prothrombin time as clinically indicated is necessary.
Auxiliary labelling: Take with food. Take with a full glass of water. May cause drowsiness. Avoid alcoholic beverages.
Store below 30 °C in a tight container.
Shelf-Life: 3 years.
M01AG01 - mefenamic acid ; Belongs to the class of non-steroidal antiinflammatory and antirheumatic products, fenamates.
Tab 500 mg (a yellow coloured, modified capsule shaped, with break line on one side) x 100 x 10's.