Does Cimetidine Interact with Metronidazole?
CDI records a moderate classification for Cimetidine and Metronidazole. The stored summary is: Cimetidine decreases microsomal liver enzyme activity, prolonging half-life and decreasing plasma clearance of metronidazole. The mechanism involves inhibition of cyp450 enzymes. Patients taking both medications should consult their healthcare provider before starting, stopping, or changing the dosage of either drug. This record was extracted from drug labeling through openFDA. NIH/NLM RxNorm is used for drug identities. The summary and severity classification are CDI's processed information, not a verbatim source quotation. Product, route, and patient circumstances matter.
Evidence status
A current label comparison is not yet available for this record. The summary and severity are stored CDI information; they have not been independently validated on this page against the exact product label.
Confirm the medicine, formulation, route, and applicable warning with your pharmacist or prescriber. Independent clinical review has not been recorded.
- Stored CDI classification
- Moderate
- Cimetidine Class
- Histamine-2 Receptor Antagonist
- Metronidazole Class
- Nitroimidazole Antimicrobial
- Management
- Confirm exact products with your pharmacist
- Data Source
- U.S. FDA via OpenFDA
Recorded Mechanism
Inhibition of CYP450 enzymes
What To Tell Your Doctor or Pharmacist
If you are taking Cimetidine and your doctor is considering prescribing Metronidazole (or vice versa), make sure to:
- Inform your doctor and pharmacist of all current medications, including over-the-counter drugs and supplements
- Ask whether the benefits of combining these medications outweigh the risks for your specific situation
- Ask what symptoms to watch for that would indicate the interaction is causing problems
- Ask whether any dosage adjustments are needed
- Never stop or change either medication without first consulting your healthcare provider