Severe. These medicines may interact and cause very harmful effects and are usually not taken together. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.
How the interaction occurs:
Magnesium trisilicate may bind to nitrofurantoin in your stomach, preventing your body from absorbing the medicine.
What might happen:
Your body may not absorb enough nitrofurantoin to fight your infection.
What you should do about this interaction:
If possible, do not take any products containing magnesium trisilicate while you are taking nitrofurantoin. If you need to take a medicine that contains magnesium trisilicate while taking nitrofurantoin, you should separate your doses of nitrofurantoin and magnesium trisilicate by as much time as possible. Also, let your healthcare professionals (e.g. doctor or pharmacist) know that you are taking these medicines together.Your healthcare professionals may already be aware of this interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.
1.Macrodantin (nitrofurantoin macrocrystals) US prescribing information. Almatica Pharma, Inc. September, 2013.
2.Macrobid (nitrofurantoin monohydrate/macrocrystals) US prescribing information. Almatica Pharma, Inc. September, 2013.
3.Naggar VF, Khalil SA. Effect of magnesium trisilicate on nitrofurantoin absorption. Clin Pharmacol Ther 1979 Jun;25(6):857-63.