Drug interactions
Diphenhydramine + Mefloquine
Severity: Moderate
Diphenhydramine and Mefloquine: 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
Diphenhydramine can prolong the QT interval, mainly in overdose or at high doses, and mefloquine may add to this effect. Both can also cause dizziness and CNS effects.
What this interaction means in plain words
Diphenhydramine and Mefloquine 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.
Diphenhydramine belongs to Respiratory; Mefloquine belongs to Anti Parasitic.
Why it happens
Possible additive QT prolongation and overlapping CNS effects.
What to do
Avoid high or repeated doses of diphenhydramine during mefloquine therapy and consider a non-sedating alternative. Monitor ECG in patients with cardiac risk factors.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Diphenhydramine and Mefloquine, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
Other interactions of Mefloquine
- Arsenic trioxide + Mefloquine Contraindicated
- Dronedarone + Mefloquine Contraindicated
- Ibutilide + Mefloquine Contraindicated
- Levoketoconazole + Mefloquine Contraindicated
- Mefloquine + Nilotinib Contraindicated
- Mefloquine + Pimozide Contraindicated
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Mefloquine?
MediHelp rates the interaction as moderate. Diphenhydramine and Mefloquine 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. Diphenhydramine can prolong the QT interval, mainly in overdose or at high doses, and mefloquine may add to this effect. Both can also cause dizziness and CNS effects.
How serious is the interaction between Diphenhydramine and Mefloquine?
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 high or repeated doses of diphenhydramine during mefloquine therapy and consider a non-sedating alternative. Monitor ECG in patients with cardiac risk factors.
What other medicines interact with Mefloquine?
MediHelp also lists interactions of Mefloquine with, for example, Arsenic trioxide, Dronedarone, Ibutilide. The full list is on the Mefloquine page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
