Interaction between Mebendazole and Metronidazole
Moderate Others

ID DDInter1128 and DDInter1202
Interaction Limited clinical data have suggested that coadministration of metronidazole and mebendazole may be associated with Stevens-Johnson syndrome/toxic epidermal necrolysis. The mechanism is unknown.
Management It is recommended that concomitant use of mebendazole and metronidazole should be avoided.
References
Alternative for Mebendazole P02C
Alternative for Metronidazole A02B
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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.