Drug interactions
Hydrochlorothiazide + Quinidine
Severity: Moderate
Hydrochlorothiazide and Quinidine: 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
Quinidine is a cation that is secreted in the renal tubule, and competition for tubular secretion with hydrochlorothiazide is theoretically possible. The more important clinical concern is that thiazide-induced hypokalemia or hypomagnesemia increases the risk of QT prolongation and torsades de pointes with quinidine. Hydrochlorothiazide levels are unlikely to change much.
What this interaction means in plain words
Hydrochlorothiazide and Quinidine 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.
Hydrochlorothiazide belongs to Cardiovascular; Quinidine belongs to Anti Parasitic.
Why it happens
Thiazide-induced hypokalemia and hypomagnesemia potentiate quinidine proarrhythmia, and the two drugs may compete for renal tubular secretion.
What to do
Check potassium and magnesium at baseline and periodically, and replace them to keep levels in the normal range. Monitor the QTc interval.
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 Quinidine
- Adagrasib + Quinidine Contraindicated
- Arsenic trioxide + Quinidine Contraindicated
- Artemether / lumefantrine + Quinidine Contraindicated
- Chloroquine + Quinidine Contraindicated
- Dofetilide + Quinidine Contraindicated
- Dronedarone + Quinidine Contraindicated
Other interactions of Hydrochlorothiazide
Frequently asked questions
Can I take Hydrochlorothiazide with Quinidine?
MediHelp rates the interaction as moderate. Hydrochlorothiazide and Quinidine 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. Quinidine is a cation that is secreted in the renal tubule, and competition for tubular secretion with hydrochlorothiazide is theoretically possible. The more important clinical concern is that thiazide-induced hypokalemia or hypomagnesemia increases the risk of QT prolongation and torsades de pointes with quinidine. Hydrochlorothiazide levels are unlikely to change much.
How serious is the interaction between Hydrochlorothiazide and Quinidine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Check potassium and magnesium at baseline and periodically, and replace them to keep levels in the normal range. Monitor the QTc interval.
What other medicines interact with Quinidine?
MediHelp also lists interactions of Quinidine with, for example, Adagrasib, Arsenic trioxide, Artemether / lumefantrine. The full list is on the Quinidine page.
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