Drug interactions
Mefloquine + Promethazine
Severity: Major
Mefloquine and Promethazine: major 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
Mefloquine can prolong the QT interval and cause cardiac conduction abnormalities, and promethazine adds to this effect. The combination may increase the risk of torsades de pointes and also add neuropsychiatric and sedative effects.
What this interaction means in plain words
Mefloquine and Promethazine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Mefloquine belongs to Anti Parasitic; Promethazine belongs to Respiratory.
Why it happens
Additive QT prolongation through cardiac ion channel effects.
What to do
Avoid the combination; use an alternative antiemetic or antihistamine. If unavoidable, obtain an ECG and monitor electrolytes.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Promethazine
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
- Amiodarone + Promethazine Major
- Amisulpride + Promethazine Major
Other interactions of Mefloquine
- Arsenic trioxide + Mefloquine Contraindicated
- Dronedarone + Mefloquine Contraindicated
- Ibutilide + Mefloquine Contraindicated
- Levoketoconazole + Mefloquine Contraindicated
- Mefloquine + Nilotinib Contraindicated
- Mefloquine + Pimozide Contraindicated
Frequently asked questions
Can I take Mefloquine with Promethazine?
MediHelp rates the interaction as major. Mefloquine and Promethazine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Mefloquine can prolong the QT interval and cause cardiac conduction abnormalities, and promethazine adds to this effect. The combination may increase the risk of torsades de pointes and also add neuropsychiatric and sedative effects.
How serious is the interaction between Mefloquine and Promethazine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination; use an alternative antiemetic or antihistamine. If unavoidable, obtain an ECG and monitor electrolytes.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Ibutilide, Pimozide, Thioridazine. The full list is on the Promethazine page.
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