Procainamide/Trimethoprim Interactions

This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.

Medical warning:

Moderate. These medicines may cause some risk when taken together. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.

How the interaction occurs:

When these two medicines are taken together, trimethoprim prevents your kidneys from processing procainamide properly.

What might happen:

You may experience an increase in the beneficial and toxic effects of procainamide.

What you should do about this interaction:

Contact your doctor if you experience weakness, fatigue, or dizziness; a fast, slow, or irregular heartbeat; lightheadedness; confusion; disorientation; depression; hallucinations; nausea; vomiting; diarrhea; stomach pain; a bitter taste in your mouth; muscle pain; fever; or rash. It may be necessary to measure your blood levels of procainamide more often.Your healthcare professionals (e.g. doctor or pharmacist) 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.Kosoglou T, Rocci ML Jr, Vlasses PH. Trimethoprim alters the disposition of procainamide and N- acetylprocainamide. Clin Pharmacol Ther 1988 Oct; 44(4):467-77.
  • 2.Vlasses PH, Kosoglou T, Chase SL, Greenspon AJ, Lottes S, Andress E, Ferguson RK, Rocci ML Jr. Trimethoprim inhibition of the renal clearance of procainamide and N- acetylprocainamide. Arch Intern Med 1989 Jun; 149(6):1350-3.

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CONDITIONS OF USE: The information in this database is intended to supplement, not substitute for, the expertise and judgment of healthcare professionals. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse effects, nor should it be construed to indicate that use of a particular drug is safe, appropriate or effective for you or anyone else. A healthcare professional should be consulted before taking any drug, changing any diet or commencing or discontinuing any course of treatment.