WARNING: RISK OF SERIOUS CARDIOVASCULAR AND GASTROINTESTINAL EVENTS:
Cardiovascular Thrombotic Events:
Non steroidal anti-inflammatory drugs (NSAIDs ) cause an increased risk ofserious cardiovascular thrombotic events , including myocardial infarction and stroke, which can be fatal. This risk may occur early in treatment and may increase with duration of use.
Mefenamic acid is contraindicated in the setting of coronary artery bypass graft (CABG) surgery .
Gastrointestinal Bleeding, Ulceration, and Perforation:
NSAIDs cause an increased risk of serious gastrointestinal (GI) adverse events including bleeding, ulceration, and perforation of the stomach or intestines , which can be fatal. These events can occur at any time during use and without warning symptoms . Elderly patients and patients with a prior history of pepticulcer disease and/or GI bleeding are at greater risk for serious GI events.
Each film coated tablet contains 500mg Mefenamic acid
cellulose, Calcium hydrogen phosphate, Cross carmellose, Sodium lauryl sulphate, Stearic acid, Polyethylene glycol and Titanium dioxide
Mechanism of action:
Mefenamic acid has demonstrated analgesic, anti-inflammatory and antipyretic properties in human clinical studies and in classical animal test systems. These effects may be due to MEFENAMIC ACID 's dual action on prostaglandins. It inhibits the enzymes of prostaglandin synthetase and also antagonises the actions of prostaglandin at the receptor sites.
Undesirable effects may be minimised by using the lowest effective dose for the shortest duration necessary to control symptoms.
Patients on long term treatment should be reviewed regularly with regards to efficacy, risk factors and ongoing need for treatment.
Dysmenorrhoea: 500 mg three times daily.
One tablet of 500 mg three times daily with meals from the onset of pain and continued for the usual duration of pain.
Menorrhagia: 2 tablets (500 mg) three times daily with meals and from the onset of menses and continued according to the judgment of the physician. Therapy should not be continued for more than 7 days except on the advice of a physician.
Other Indications: 2 tablets (500 mg) three times daily, with meals.
Use in the Elderly and Renal Dysfunction :
Caution is required with dosage in the elderly and patients with renal dysfunction.
Signs and Symptoms: Symptoms of overdosage are related to the amount of drug ingested and range from gastrointestinal discomfort and diarrhoea to seizures, acute renal failure, confusional state, vertigo, hallucination, coma and death. Plasma levels of up to 210 mcg/mL (therapeutic range 1 to 10 mcg/mL) have been reported resulting in repeated generalised convulsions, but are not generally useful for evaluation and management of overdosage.
Treatment: There is no specific antidote for mefenamic acid overdose. Treatment is symptomatic and supportive, including fluid replacement and IV access especially to patients who are dehydrated or unable to ingest adequate fluids. Avoiding intravascular fluid depletion will help prevent development of renal failure. In cases of severe toxicity, activated charcoal may reduce absorption of the drug if given within one to two hours after ingestion. In patients who are not fully conscious or have impaired gag reflex, consideration should be given to administering activated charcoal via nasogastric tube ensuring that the airway is protected. In clinically severe overdoses, full blood count, electrolytes, glucose, renal function, liver function tests, arterial blood gases and coagulation studies should be monitored for abnormalities. Because mefenamic acid and its metabolites are firmly bound to plasma proteins, haemodialysis, haemoperfusion and peritoneal dialysis may be of little value.
Aspirin: Mefenamic acid interferes with the anti-platelet effect of low-dose aspirin, and thus may interfere with aspirin’s prophylactic treatment of CV disease.
Anticoagulants: The concurrent use of NSAIDs and warfarin has been associated with severe, sometimes fatal, haemorrhage. Mefenamic acid, like other non-steroidal anti-inflammatory agents, can inhibit platelet aggregation and may prolong prothrombin time in patients on warfarin therapy. Mefenamic acid has been shown to displace warfarin from protein binding sites and may enhance the response to oral anticoagulants. NSAIDs, such as Mefenamic acid, should be used in combination with warfarin, only if absolutely necessary. Concurrent administration of Mefenamic acid with oral anticoagulant drugs requires frequent prothrombin time monitoring .
Anti-hypertensives: NSAIDs, such as Mefenamic acid, can reduce the efficacy of anti-hypertensive drugs including diuretics, angiotensin-converting enzyme (ACE) inhibitors, angiotensin II antagonists (AIIAs) and beta-blockers.
Therefore, the concomitant administration of these drugs should be done with caution, especially in elderly patients. Patients should be adequately hydrated and the need to monitor renal function should be assessed before, and periodically during, concomitant treatment.
Corticosteroids: Concurrent use with NSAIDs may increase the risk of gastrointestinal ulceration or bleeding.
Cyclosporin or Tacrolimus: Concomitant administration with NSAIDs increases the risk of nephrotoxicity.
Hypoglycaemic agents: There have been reports of changes in the effects of oral hypoglycaemic agents in the presence of NSAIDs. Therefore, Mefenamic acid should be administered with caution in patients receiving insulin or oral hypoglycaemic agents.
Lithium: Mefenamic acid has produced an elevation of plasma lithium levels and a reduction in renal lithium clearance. Thus, when Mefenamic acid and lithium are administered concurrently, patients should be observed carefully for signs of lithium toxicity.
Methotrexate: Caution is advised when methotrexate is administered concurrently with NSAIDs, including Mefenamic acid, because NSAID administration may result in increased plasma levels of methotrexate, especially in patients receiving high doses of methotrexate.
NSAIDs, including Mefenamic acid, can cause serious, potentially fatal gastrointestinal (GI) adverse events including inflammation, bleeding, ulceration and perforation of the stomach, small intestine or large intestine. The frequency of such events may increase with dose or duration of use, but can occur at any time without warning.
Upper GI ulcers, gross bleeding or perforation caused by NSAIDs occur in approximately 1% of patients treated for 3-6 months and in about 2-4% of patients treated for one year. These trends continue with longer duration of use, increasing the likelihood of developing a serious GI event at some time during the course of therapy. However, even short term therapy is not without risk.
Patients most at risk of developing GI complications with NSAIDs are the elderly; patients with CV disease; patients using concomitant corticosteroids, antiplatelet drugs (such as aspirin), or selective serotonin reuptake inhibitors (SSRIs); patients with a history of, or active, GI disease (such as ulceration, bleeding or inflammatory conditions); and patients ingesting alcohol or with a history of smoking and alcoholism. Mefenamic acid should be used with caution in these patients.
NSAIDs may very rarely cause serious cutaneous adverse events such as exfoliative dermatitis, toxic epidermal necrolysis (TEN) and Stevens-Johnson syndrome (SJS), which can be fatal and occur without warning. These serious adverse events are idiosyncratic and are independent of dose or duration of use. Patients should be advised of the signs and symptoms of serious skin reactions and to consult their doctor at the first appearance of a skin rash, mucosal lesion or any other sign of hypersensitivity. If this occurs, the drug should be promptly discontinued.
Mefenamic acid may cause an exacerbation of chronic urticaria in patients with this disease.
As with other NSAIDs, long-term administration of Mefenamic acid to animals has resulted in renal papillary necrosis and other abnormal renal pathology. In humans, there have been reports of acute interstitial nephritis with haematuria, proteinuria, glomerulitis, papillary necrosis and occasionally nephrotic syndrome.
A second form of renal toxicity has been seen in patients with pre-renal conditions leading to a reduction in renal blood flow or blood volume, where the renal prostaglandins have a supportive role in the maintenance of renal perfusion. In these patients, administration of an NSAID may cause a dose-dependent reduction in prostaglandin formation and may precipitate overt renal decomposition. Patients at greatest risk of this reaction are those with impaired renal function, heart failure, liver dysfunction, nephrotic syndrome, those taking diuretics and the elderly. Such patients should be carefully monitored while receiving Mefenamic acid.
Discontinuation of NSAID therapy is typically followed by recovery to the pre-treatment state. Since Mefenamic acid is eliminated primarily by the kidneys, the drug should not be administered to patients with significantly impaired renal functions .
Mefenamic acid should be used with caution in patients with hepatic impairment. Physicians and patients should remain alert for hepatotoxicity. Patients should be informed about the signs and/or symptoms of hepatotoxicity. A patient with symptoms and/or signs suggesting occur (e.g. eosinophilia, rash, etc.), Mefenamic acid should be discontinued.
Mefenamic acid 500 mg and aspirin 650 mg, four times a day, both caused significant further lowering of the prothrombin concentration in patients in whom the concentration has been initially lowered by anticoagulant therapy. Caution should therefore be exercised in administering Mefenamic acid to patients on anticoagulant therapy, such as warfarin, and should not be given when prothrombin concentration is in the range of 10% to 20% of normal. Careful monitoring of blood coagulation factors is recommended .
The concomitant use of NSAIDs, including Mefenamic acid, with oral anticoagulants increases the risk of GI and non-GI bleeding and should be given with caution. Oral anticoagulants include warfarin/coumarin-type and novel oral anticoagulants (e.g. apixaban, dabigatran, rivaroxaban). Anticoagulation/INR should be monitored in patients taking a warfarin/coumarin-type anticoagulant .
Mefenamic acid should be used with caution in known asthmatics.
As no data presently exist concerning the effect of MEFENAMIC ACID , if any, on the efficacy of intrauterine contraceptive devices, physicians should be alert to the possibility of a reduction in contraceptive efficacy in women with an IUCD taking Mefenamic acid.
Use in Pregnancy or Lactation:
Since there are no adequate and well-controlled studies in pregnant women, Mefenamic acid should be used only if the potential benefits to the mother justify the possible risks to the fetus. It is not known if Mefenamic acid or its metabolites crosses the placenta. NSAIDs given during the latter part of pregnancy may cause closure of the fetal ductusarteriosus, fetal renal impairment, inhibition of platelet aggregation, and delay labour and birth. Because of the effects of drugs in this class (i.e. inhibitors of prostaglandin synthesis) on the fetal CV system (i.e. premature closure of the ductusarteriosus), the use of Mefenamic acid in pregnant women is not recommended and should be avoided during the third trimester of pregnancy, including the last few days before expected birth. Mefenamic acid inhibits prostaglandin synthesis which may result in prolongation of pregnancy and interference with labour when administered late in the pregnancy. Women on Mefenamic acid therapy should consult their physician if they decide to become pregnant. If used during second or third trimester of pregnancy, NSAIDs may cause fetal renal dysfunction which may result in reduction of amniotic fluid volume or oligohydramnios in severe cases. Such effects may occur shortly after treatment initiation and are usually reversible. Pregnant women on Mefenamic acid should be closely monitored for amniotic fluid volume.
Trace amounts of Mefenamic acid may be present in breast milk and transmitted to the nursing infant. Thus Mefenamic acid should not be taken by the nursing mother because of the effects of this class of drugs on the infant cardiovascular system.
Based on the mechanism of action, the use of NSAIDs may delay or prevent rupture of ovarian follicles, which has been associated with reversible infertility in some women. In women who have difficulties conceiving or who are undergoing investigation of infertility, withdrawal of NSAIDs, including Mefenamic acid , should be considered.
Single and multiple studies have shown that Mefenamic acid usually reaches peak plasma levels 2 to 4 hours after oral administration with a half-life of 2 hours.
Distribution: Mefenamic acid and its metabolites are firmly bound to plasma proteins.
Biotransformation: Mefenamic acid metabolism is predominantly mediated via cytochrome P450 CYP 2C9 in the liver.
Elimination: Following a single dose, 67% of the total dose is excreted in the urine as unchanged drug or as one of the two metabolites. 20% to 25% of the dose is excreted in the faeces during the first three days.