What is a side effect of triamterene?

A. Neutropenia: Triamterene does not typically suppress bone marrow or reduce white blood cell counts. Hematologic effects are not a recognized adverse effect of this potassium-sparing diuretic. B. Bradycardia: Triamterene does not directly slow the heart rate. However, extreme hyperkalemia can cause EKG changes (like peaked T-waves or widened QRS complexes) that might eventually lead to heart block, but the primary electrolyte issue is the direct side effect. C. Urinary retention: Diuretics are designed to increase urine output. Urinary retention (the inability to empty the bladder) is usually associated with anticholinergic drugs or prostate issues, not potassium-sparing diuretics. D. Hyperkalemia: Triamterene inhibits sodium reabsorption in exchange for potassium excretion in the distal nephron, leading to potassium retention. Elevated serum potassium can cause muscle weakness, cardiac arrhythmias, and requires close monitoring, making hyperkalemia the most significant side effect.