MajorSulfonamide-trimethoprim combination×Angiotensin II receptor blockers (ARBs)
Updated · Methodology
Mechanism
Trimethoprim blocks collecting duct sodium channels (amiloride-like mechanism) and reduces potassium secretion. Valsartan (ARB) additionally retains potassium through aldosterone suppression.
Symptoms
Muscle weakness, paraesthesia in the limbs, slowed pulse, arrhythmias. ECG shows peaked T waves and widened QRS. Severe cases progress to cardiac arrest. Symptoms typically appear within 1–2 weeks of starting the combination.
Management
During co-trimoxazole therapy, check potassium 3–5 days after start. In older patients and chronic kidney disease, prefer alternative antibiotics: nitrofurantoin or fosfomycin.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.
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