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250 mg: Aspirin and Other NSAIDs: Mefenamic acid should not be given together with aspirin, salicylates or other NSAIDs (e.g., ketorolac, ibuprofen, naproxen) including COX-2 inhibitors (e.g., celecoxib, etoricoxib) because of the increased risk of stomach and intestinal bleeding.
Corticosteroids, Selective Serotonin-Reuptake Inhibitors (SSRIs), and Anti-platelet Agents: May increase the risk of stomach bleeding with mefenamic acid.
Aminoglycosides: NSAIDs, such as mefenamic acid, increase aminoglycoside toxicity by decreasing the excretion of aminoglycoside antibiotics (e.g., amikacin, gentamicin, neomycin, tobramycin).
Antacids: The plasma levels of mefenamic acid may be increased when taken together with antacids such as magnesium hydroxide.
Antihypertensives and Diuretics: NSAIDS may reduce the effect of these drugs; diuretics may also cause acute reduction in kidney function of NSAIDs.
Blood Thinning Medicines (Anticoagulants): NSAIDs may enhance the effects of these agents (e.g., warfarin). An increase in the International Normalized Ratio (INR), which may serve as a sign of increased risk for bleeding, may be observed when using paracetamol and warfarin at the same time.
Cardiac Glycosides: NSAIDs may worsen heart failure, reduce kidney function and increase blood levels of these medicines (e.g., digoxin).
Ciclosporin and Tacrolimus: Increased risk of kidney damage.
Lithium and Methotrexate: Mefenamic acid increases the amount of lithium and methotrexate in the blood, thus increasing the risk of toxicity.
Medicines Affecting Liver Enzymes: Medicines which hinder the enzymes responsible for the metabolism of mefenamic acid may alter its safety and efficacy.
Medicines that Lower Blood Sugar (for Diabetes): Mefenamic acid may increase plasma levels of medicines used to treat diabetes (sulfonylureas such as gliclazide, glipizide, glimepiride) by inhibiting their metabolism.
Mifepristone: Mefenamic acid should not be used for 8 to 12 days after mifepristone administration because it can reduce the effect of mifepristone.
Probenecid: May reduce the metabolism and excretion of mefenamic acid, thus increasing the risk of mefenamic acid toxicity.
Quinolone Antibiotics: A possible increased risk of convulsions may occur with mefenamic acid.
Zidovudine: An increased risk of blood problems such as bleeding into a joint (hemarthrosis) and bruising (hematoma) may result when given with mefenamic acid.
500 mg: See table.
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