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Home > Emergency Medical Minute > Episode 948: CYP Inducers and Inhibitors
Podcast: Emergency Medical Minute
Episode:

Episode 948: CYP Inducers and Inhibitors
Category: Science & Medicine
Duration: 00:03:57
Publish Date: 2025-03-17 10:00:00
Description:

Contributor: Jorge Chalit-Hernandez, OMS3

Educational Pearls:

  • CYP enzymes are responsible for the metabolism of many medications, drugs, and other substances

    • CYP3A4 is responsible for the majority

    • Other common ones include CYP2D6 (antidepressants), CYP2E1 (alcohol), and CYP1A2 (cigarettes)

  • CYP inducers lead to reduced concentrations of a particular medication

  • CYP inhibitors effectively increase concentrations of certain medications in the body

  • Examples of CYP inducers

    • Phenobarbital

    • Rifampin 

    • Cigarettes

    • St. John’s Wort

  • Examples of CYP inhibitors

    • -azole antifungals like itraconazole and ketoconazole

    • Bactrim (trimethoprim-sulfamethoxazole)

    • Ritonavir (found in Paxlovid)

    • Grapefruit juice

  • Clinical relevance

    • Drug-drug interactions happen frequently and often go unrecognized or underrecognized in patients with significant polypharmacy

    • A study conducted on patients receiving Bactrim and other antibiotics found increased rates of anticoagulation in patients receiving Bactrim

    • Currently, Paxlovid is prescribed to patients with COVID-19, many of whom have multiple comorbidities and are on multiple medications

      • Paxlovid contains ritonavir, a powerful CYP inhibitor that can increase concentrations of many other medications

  • A complete list of clinically relevant CYP inhibitors can be found on the FDA website:

    • https://www.fda.gov/drugs/drug-interactions-labeling/drug-development-and-drug-interactions-table-substrates-inhibitors-and-inducers 

References

  1. Glasheen JJ, Fugit RV, Prochazka AV. The risk of overanticoagulation with antibiotic use in outpatients on stable warfarin regimens. J Gen Intern Med. 2005;20(7):653-656. doi:10.1111/j.1525-1497.2005.0136.x

  2. Lynch T, Price A. The effect of cytochrome P450 metabolism on drug response, interactions, and adverse effects. Am Fam Physician. 2007;76(3):391-396.

  3. PAXLOVID™. Drug interactions. PAXLOVIDHCP. Accessed March 16, 2025. https://www.paxlovidhcp.com/drug-interactions

Summarized & Edited by Jorge Chalit, OMS3

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