Interaction between Activated charcoal and Ipecac
Moderate Antagonism

ID DDInter24 and DDInter968
Interaction Administration of activated charcoal with ipecac may decrease the effectiveness of the ipecac. The alkaloids of ipecac may be adsorbed onto the charcoal. The concomitant use of ipecac and charcoal does not appear to improve patient outcome over charcoal alone.
Management Ipecac and activated charcoal are generally not administered together routinely; although the prior administration of one agent should not be considered a contraindication to the administration of the other agent if it is deemed necessary by the attending physician. If both agents are used to treat a patient, the ipecac is generally given first and the charcoal is given after vomiting has stopped.
References
Alternative for Activated charcoal A07B
Alternative for Ipecac R05C

V03A
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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.