Interaction between Loperamide and Nefazodone
Major Metabolism

ID DDInter1088 and DDInter1274
Interaction Coadministration with drugs that enhance the gastrointestinal absorption or inhibit the metabolism of loperamide (e.g., potent CYP450 3A4 or 2C8 inhibitors) may increase the plasma concentrations and adverse effects of loperamide.
abdominal pain Anxiety arthritis Back Ache chest pain constipated Bladder inflammation diarrhea dizziness drowsiness More
Management Caution is recommended if loperamide is used with drugs that enhance its gastrointestinal absorption or inhibit its metabolism. Particular caution is advised when drugs that inhibit CYP450 3A4 (e.g., azole antifungal agents, clarithromycin, cobicistat, conivaptan, delavirdine, erythromycin, idelalisib, nefazodone, protease inhibitors, telithromycin) and CYP450 2C8 (e.g., gemfibrozil, clopidogrel) are used together with loperamide, or when one or more of these drugs are combined with inhibitors of P-glycoprotein transport (e.g., amiodarone, cyclosporine, diltiazem, dronedarone, quinidine, verapamil), since they may act synergistically to increase loperamide concentrations. Patients should be counseled to not exceed the recommended dosage and frequency or duration of use of loperamide, and to seek prompt medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, lightheadedness, fainting, palpitation, irregular heart rhythm, shortness of breath, or syncope. If loperamide-induced cardiotoxicity is suspected, promptly discontinue loperamide and initiate therapy to manage and prevent cardiac arrhythmias and adverse outcomes. Electrical pacing or cardioversion may be necessary if torsade de pointes persists despite pharmacotherapy.
References
Alternative for Loperamide A07D
Difenoxin
Diphenoxylate
Alternative for Nefazodone N06A
Isocarboxazid
Tryptophan
Vilazodone
Desvenlafaxine
Vortioxetine
Fluvoxamine
Phenelzine
Milnacipran
Oxitriptan
Tranylcypromine
St. John's Wort

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.