MajorACE inhibitor×Sulfonamide-trimethoprim combination
Updated · Methodology
Mechanism
Trimethoprim (a co-trimoxazole component) blocks sodium channels in the collecting duct epithelium (amiloride-like mechanism) and reduces potassium secretion. Captopril (ACE-I) additionally retains potassium via 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 (usually 5–10 days), check potassium 3–5 days after start. In older patients and chronic kidney disease, prefer alternative antibiotics: nitrofurantoin or fosfomycin for urinary tract infection.
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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