Drug interactions
Cimetidine + Valacyclovir
Severity: Minor
Cimetidine and Valacyclovir: minor 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 slightly decreases renal clearance of acyclovir, the active metabolite of valacyclovir, raising exposure. This is rarely clinically important except in renal impairment, where neurotoxicity may occur.
What this interaction means in plain words
Cimetidine and Valacyclovir have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Cimetidine belongs to Gastrointestinal Tract; Valacyclovir belongs to Anti Virals.
Why it happens
Cimetidine competes with acyclovir for renal tubular secretion via organic anion/cation transporters.
What to do
No adjustment is needed with normal renal function; in renal impairment monitor for confusion or neurotoxicity and dose by creatinine clearance.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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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 Valacyclovir
- Talimogene laherparepvec + Valacyclovir Major
- Bacitracin + Valacyclovir Moderate
- Cilastatin-imipenem + Valacyclovir Moderate
- Elvitegravir / cobicistat / emtricitabine / tenofovir df + Valacyclovir Moderate
- Imipenem / cilastatin / relebactam + Valacyclovir Moderate
- Imipenem / cilastatin + Valacyclovir Moderate
Frequently asked questions
Can I take Cimetidine with Valacyclovir?
MediHelp rates the interaction as minor. Cimetidine and Valacyclovir have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Cimetidine slightly decreases renal clearance of acyclovir, the active metabolite of valacyclovir, raising exposure. This is rarely clinically important except in renal impairment, where neurotoxicity may occur.
How serious is the interaction between Cimetidine and Valacyclovir?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: No adjustment is needed with normal renal function; in renal impairment monitor for confusion or neurotoxicity and dose by creatinine clearance.
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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