Magnesium and Nitrofurantoin interaction
Magnesium and Nitrofurantoin: the Nitrofurantoin prescribing label flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Nitrofurantoin label · effective 2025-11-11
If coadministration of nitrofurantoin with antacids containing magnesium trisilicate cannot be avoided, monitor for lack of efficacy [see Clinical Pharmacology (12.3) ].
Antacids Antacids containing magnesium trisilicate, when administered concomitantly with nitrofurantoin, reduce both the rate and extent of absorption.
The mechanism for this interaction probably is adsorption of nitrofurantoin onto the surface of magnesium trisilicate.
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Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.