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:
Trimethoprim decreases the ability of your kidneys to remove dofetilide.
What might happen:
When taken with trimethoprim, your blood levels of dofetilide may increase. This may cause life-threatening effects to your heart.
What you should do about this interaction:
Contact your healthcare professionals (e.g. doctor or pharmacist) as soon as possible about taking these two medicines together. They 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.Tikosyn (dofetilide) US prescribing information. Pfizer Inc. February, 2011.