Serious. These medicines may interact and cause very harmful effects. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.
How the interaction occurs:
When these two medicines are taken together, your antibiotic may not be effective at curing your infection.
What might happen:
Your antibiotic may not work correctly and may result in worsening of your urinary infection.
What you should do about this interaction:
If you experience problems or pain when urinating, fever, or pain in your side, contact your healthcare professionals (e.g. doctor or pharmacist) about taking these two 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.Reference:1.Visqid A/A (methenamine and sodium acid phosphate monohydrate) US prescribing information. January, 2007.