Drug interactions
Cimetidine + Ketoconazole
Severity: Moderate
Cimetidine and Ketoconazole: 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
Oral ketoconazole requires an acidic stomach for dissolution, and cimetidine raises gastric pH, which can markedly reduce ketoconazole absorption. This may cause antifungal treatment failure.
What this interaction means in plain words
Cimetidine and Ketoconazole 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; Ketoconazole belongs to Anti Fungals.
Why it happens
Elevated gastric pH from H2 blockade reduces dissolution and absorption of ketoconazole.
What to do
Avoid concurrent use if possible; otherwise give ketoconazole at least 2 hours before the H2 blocker, or with an acidic beverage, and monitor antifungal response.
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 Ketoconazole
- Alfuzosin + Ketoconazole Contraindicated
- Alprazolam + Ketoconazole Contraindicated
- Avanafil + Ketoconazole Contraindicated
- Conivaptan + Ketoconazole Contraindicated
- Dihydroergotamine intranasal + Ketoconazole Contraindicated
- Dihydroergotamine + Ketoconazole Contraindicated
Frequently asked questions
Can I take Cimetidine with Ketoconazole?
MediHelp rates the interaction as moderate. Cimetidine and Ketoconazole 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. Oral ketoconazole requires an acidic stomach for dissolution, and cimetidine raises gastric pH, which can markedly reduce ketoconazole absorption. This may cause antifungal treatment failure.
How serious is the interaction between Cimetidine and Ketoconazole?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid concurrent use if possible; otherwise give ketoconazole at least 2 hours before the H2 blocker, or with an acidic beverage, and monitor antifungal response.
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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