Brand Name: MEFENAX FORTE/ MEFENAX
Generic Name: Mefenamic acid
Preparations: MEFENAX FORTE: Mefenamic acid 500 mg and MEFENAX: Mefenamic acid 250 mg Tablets
Pharmacological Category: NSAIDs
Mechanism of Action (MOA)
Mefenamic acid inhibits synthesis of prostaglandins in body tissues by inhibiting cyclooxygenase isoenzymes, (COX-I and COX-II). It may also inhibit chemotaxis, alter lymphocyte activity, decrease proinflammatory cytokine activity and inhibit neutrophil aggregation.
Pharmacokinetics
Absorption: Absorbed from the gastrointestinal tract
Peak Plasma Concentrations: About 2 to 4 hours after ingestion
Protein Binding: More than 90%
Distribution: Distributed into breast milk
Metabolism: Metabolised by the cytochrome P450 isoenzyme CYP2C9 to 3-hydroxymethyl mefenamic acid, which may then be oxidised to 3-carboxymefenamic acid
Elimination half-life: About 2 to 4 hours
Excretion: Urine (over 50%)
Indications and Dosage
• Mild to moderate pain including a headache, dental pain, postoperative and postpartum pain
• Dysmenorrhoea
• Musculoskeletal and joint disorders such as osteoarthritis and rheumatoid arthritis
• Menorrhagia
Dose: 500 mg TID or initially 500 mg followed by 250 mg every 6 hours as needed
Duration: Should not be given for longer than 7 days at a time.
Side Effects
• Common: gastrointestinal discomfort, nausea, diarrhoea
• Others: peptic ulceration, severe gastrointestinal bleeding, drowsiness and effects on the blood such as thrombocytopenia, occasionally haemolytic anemia
• Rare: aplastic anaemia
• Overdosage: Convulsion
Contraindications
Inflammatory bowel disease, active peptic ulceration, severe heart failure, hypersensitivity to mefenamic acid, aspirin or other NSAIDs
Warnings/ Precautions
• Treatment should be stopped if diarrhoea and rashes occur.
• Blood counts and liver and renal function should be monitored during long-term therapy.
• Drowsiness may affect the performance of skilled tasks.
• May be taken with or after food or milk. Also, H2-antagonist and PPI may be used to reduce the risk of gastrointestinal effects.
• May give a false positive in some tests for the presence of the bile in the urine
• Caution in patients with hypertension, infections, asthma or allergic disorders, haemorrhagic disorders, impaired renal or hepatic function and history of peptic ulceration
• Caution in the elderly and may need to be given in reduced doses.
Drug Interactions
• NSAIDs enhance the effects of oral anticoagulants.
• NSAIDs increase the plasma concentrations of lithium, methotrexate and cardiac glycosides.
• Increased risk of nephrotoxicity if given with ACE inhibitors, cyclosporin, tacrolimus, or diuretics.
• Increased risk of hyperkalaemia if given with ACE inhibitors and potassium sparing diuretics.
• The antihypertensive effects of some antihypertensives including ACE inhibitors, beta blockers, and diuretics may be reduced.
• Convulsions may occur if given with quinolones.
• NSAIDs may increase the effects of phenytoin and sulfonylurea antidiabetics.
• Use of more than one NSAID together should be avoided because of the increased risk of adverse effects.
• The risk of gastrointestinal bleeding and ulceration associated with NSAIDs is increased when used with corticosteroids, the SSRIs, the SNRI venlafaxine, the antiplatelets clopidogrel and ticlopidine, iloprost, erlotinib, sibutramine, or possibly, alcohol, bisphosphonates or pentoxifylline.
• There may be an increased risk of haematotoxicity if used with zidovudine.
• Ritonavir may increase the plasma concentrations of NSAIDs.
Pregnancy Category: C; D if used for prolonged periods, or near term (premature closure of ductus arteriosus)
Presentations
MEFENAX FORTE: 20 x 10’s
MEFENAX: 10 x 10’s