Interaction between Mefenamic acid and Apixaban
Major Synergy

ID DDInter1139 and DDInter108
Interaction Concomitant use of apixaban with other agents that alter hemostasis such as aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), platelet aggregation inhibitors, other anticoagulants, thrombolytic agents, or drugs that cause thrombocytopenia may increase the risk of bleeding. In patients receiving neuraxial anesthesia or spinal puncture, the risk of developing an epidural or spinal hematoma during apixaban therapy may also be increased by the concomitant use of other drugs that affect coagulation. The development of epidural and spinal hematoma can lead to long-term neurological injury or permanent paralysis.
Management Caution is recommended if apixaban must be used with other agents that alter hemostasis. Patients should be monitored for increased anticoagulant effects and bleeding complications. In patients undergoing neuraxial intervention, coadministration of these agents should be approached with caution and only after thorough assessment of risks and benefits. Besides bleeding complications, patients should also be monitored frequently for signs and symptoms of neurologic impairment such as midline back pain, sensory and motor deficits (numbness or weakness in lower limbs), and bowel or bladder dysfunction.
References
Alternative for Mefenamic acid M01A
Alternative for Apixaban B01A

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.