MajorSulfonamide-trimethoprim combination×Angiotensin II receptor blocker (ARB)
Updated · Methodology
Mechanism
Trimethoprim in co-trimoxazole blocks the epithelial sodium channel (ENaC) like amiloride – potassium retention. With an ARB (telmisartan): additive hyperkalaemia.
Symptoms
Muscle weakness, paraesthesia, slowed pulse, arrhythmias. ECG: peaked T waves, widened QRS. Severe cases progress to cardiac arrest.
Management
During co-trimoxazole therapy, check potassium 3 days after start. In older patients and chronic kidney disease, prefer alternative antibiotics (nitrofurantoin, 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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