Hydrochlorothiazide

ACE inhibitors, beta-blockers, calcium channel blockers, and ARBs are all preferred over HCTZ for initial antihypertensive therapy. HCTZ-induced hypokalemia causes muscular weakness and, in cardiac patients, directly increases arrhythmia risk. Overly rapid correction of HCTZ-induced hyponatremia can cause central pontine myelinolysis, a dangerous swelling of the brainstem. HCTZ's continuous diuretic effect regardless of fluid status can cause profound dehydration when layered on top of an intercurrent illness. HCTZ-induced hyponatremia is particularly dangerous in older women, potentially causing confusion, seizures, and requiring slow hospital correction.