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.