Drug interactions
Cimetidine + Metformin
Severity: Moderate
Cimetidine and Metformin: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Cimetidine raises metformin plasma levels and reduces its renal clearance. This increases the risk of metformin accumulation and, rarely, lactic acidosis, especially in renal impairment.
What this interaction means in plain words
Cimetidine and Metformin can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Cimetidine belongs to Gastrointestinal Tract; Metformin belongs to Endocrine.
Why it happens
Cimetidine inhibits renal tubular secretion of metformin via OCT2 and MATE transporters.
What to do
Monitor glycemic control and renal function, and consider a metformin dose reduction; prefer famotidine or a proton pump inhibitor in patients at risk of accumulation.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Cimetidine
- Cimetidine + Dofetilide Contraindicated
- Cimetidine + Fezolinetant Contraindicated
- Alfentanil + Cimetidine Major
- Atazanavir + Cimetidine Major
- Carmustine + Cimetidine Major
- Cimetidine + Citalopram Major
Other interactions of Metformin
Frequently asked questions
Can I take Cimetidine with Metformin?
MediHelp rates the interaction as moderate. Cimetidine and Metformin can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Cimetidine raises metformin plasma levels and reduces its renal clearance. This increases the risk of metformin accumulation and, rarely, lactic acidosis, especially in renal impairment.
How serious is the interaction between Cimetidine and Metformin?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor glycemic control and renal function, and consider a metformin dose reduction; prefer famotidine or a proton pump inhibitor in patients at risk of accumulation.
What other medicines interact with Cimetidine?
MediHelp also lists interactions of Cimetidine with, for example, Dofetilide, Fezolinetant, Alfentanil. The full list is on the Cimetidine page.
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