Interaction between Mefenamic acid and Omega-3 fatty acids
Moderate Synergy

ID DDInter1139 and DDInter1339
Interaction Omega-3 fatty acids (e.g., fish oil) may potentiate the pharmacologic effects of anticoagulants and other drugs that affect hemostasis such as platelet inhibitors, thrombin inhibitors, thrombolytic agents, dextran, and nonsteroidal anti-inflammatory drugs (NSAIDs). The exact mechanism of interaction is unknown. Omega-3 fatty acids may possess mild antiplatelet and hypocoagulant activities.
Management In general, patients should consult a healthcare provider before taking any herbal or nutritional supplements. Patients using omega-3 fatty acids in combination with anticoagulants or other drugs that affect hemostasis should be advised of the potential for increased risk of bleeding complications.
References
Alternative for Mefenamic acid M01A
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Alternative for Omega-3 fatty acids -

Potential Metabolism Interactions

Substrate-Substrate Interaction:If more than one drug is metabolized by the same CYP, it is possible that its metabolism is inhibited because of the competition between the drugs. That means, it can be useful to lower the dosage of the drugs in the drug-cocktail because they remain longer in the organism than in monotherapy.
Inhibitor-Inhibitor Interaction:Combining two or more inhibitors of one CYP, should be compensated by lowering the dosage of these drugs because the metabolism is reduced and the drugs remain longer in the organism than in monotherapy. Not adapting the dosage bears the risk of even more side effects.
Inhibitor-Substrate Interaction:Combining drugs that have inhibitory effect and are substrates of one particular CYP, should be compensated by lowering the dosage. They rest longer in the organism than in monotherapy. Not adapting the dosage bears the risk of even more side effects.