NutriStack
Magnesium Glycinate and Ondansetron, a caution.
Ondansetron can prolong the QT interval and rare cases of torsades de pointes have been reported, especially with IV dosing or predisposing risks. Low magnesium is a known risk factor for drug-induced long QT and torsades. Maintaining normal magnesium status lowers this background risk, particularly during vomiting, diarrhea, diuretic use, or poor intake.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
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At a glance
- Substances
- Magnesium Glycinate and Ondansetron
- Pair type
- Caution
- Evidence (highest tier)
- Moderate
- Source citations
- 3 sources
- Stack Score effect
- −5 to your Stack Score (per scored caution row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Caution · Moderate evidence
Caution
What is happening. Ondansetron can prolong the QT interval and rare cases of torsades de pointes have been reported, especially with IV dosing or predisposing risks. Low magnesium is a known risk factor for drug-induced long QT and torsades. Maintaining normal magnesium status lowers this background risk, particularly during vomiting, diarrhea, diuretic use, or poor intake.
Mechanism. Ondansetron can delay cardiac repolarization, partly through effects on cardiac potassium currents. Hypomagnesemia reduces repolarization reserve and promotes early afterdepolarizations, making torsades more likely in the presence of QT-prolonging drugs.
Recommendation. Do not take high-dose magnesium without medical advice, but maintain normal magnesium intake while using ondansetron if you have ongoing GI losses or QT-risk factors. Ask about checking electrolytes if you need repeated ondansetron doses, have heart disease, take other QT-prolonging drugs, or have severe vomiting or diarrhea. Seek urgent care for fainting, palpitations, or seizure-like episodes.
Sources (3)
- Orozco BS, Lee SC, Fuchs RT, Fushianes GD, Cole JB. QT prolongation, torsades des pointes, and cardiac arrest after 4 mg of IV ondansetron. Am J Emerg Med. 2023;68:214.e3-214.e6. PMID 37085406
- Lee DY, Trinh T, Roy SK. Torsades de Pointes after Ondansetron Infusion in 2 Patients. Tex Heart Inst J. 2017;44(5):366-369. PMID 29259513
- TeBay C, Hill AP, Windley MJ. Metabolic and electrolyte abnormalities as risk factors in drug-induced long QT syndrome. Biophys Rev. 2022;14(1):353-367. PMID 35103080
Stack Score
How this pair moves the number.
Effect on the composite score
If both Magnesium Glycinate and Ondansetron are in the same stack, this pair applies −5 to your Stack Score (per scored caution row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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