Drug interactions
Cimetidine + Melatonin
Severity: Minor
Cimetidine and Melatonin: 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 can raise melatonin concentrations because melatonin is cleared mainly via CYP1A2. This may increase daytime drowsiness and sedation.
What this interaction means in plain words
Cimetidine and Melatonin 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; Melatonin belongs to Gastrointestinal Tract.
Why it happens
Cimetidine inhibits CYP1A2-mediated hepatic metabolism of melatonin.
What to do
Use the lowest effective melatonin dose and watch for excessive sedation or next-day drowsiness.
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 Melatonin
- Fluvoxamine + Melatonin Major
- Alfentanil + Melatonin Moderate
- Belladonna and opium + Melatonin Moderate
- Buprenorphine buccal + Melatonin Moderate
- Butabarbital + Melatonin Moderate
- Butalbital + Melatonin Moderate
Frequently asked questions
Can I take Cimetidine with Melatonin?
MediHelp rates the interaction as minor. Cimetidine and Melatonin 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 can raise melatonin concentrations because melatonin is cleared mainly via CYP1A2. This may increase daytime drowsiness and sedation.
How serious is the interaction between Cimetidine and Melatonin?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Use the lowest effective melatonin dose and watch for excessive sedation or next-day drowsiness.
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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