Question: The co-ingestion of drugs in which class may potentiate the adverse effects of the drug loperamide?
Answer: According to the cited reference. “Loperamide is actively removed from the central nervous system by p-glycoprotein, a membrane transporter at the blood brain barrier, and therefore ingestion of P-glycoprotein inhibitors (e.g. amiodarone, macrolide antibiotics, ketoconazole, quinidine and verapamil) potentiates euphoria or anti-withdrawal effects.” These authors also note “Further potentiation can be achieved with drugs that inhibit hepatic metabolism of the drug.” (Bellew S and Barrett TW. Loperamide will stop you up but it can also bring you down. 2017 Ann Emerg Med 69(6):786-791)