Early-Onset Thiazide-Induced Hyponatremia Leading to Seizure in a Middle-Aged Woman Using Aldactazide

Thiazide-induced hyponatremia (TIH) is a well-recognized adverse effect of thiazide diuretics, typically occurring in elderly individuals. Severe acute hyponatremia presenting with seizures in middle-aged adults is uncommon. Combination therapy with spironolactone and hydrochlorothiazide (Aldactazide) may increase susceptibility to rapid electrolyte shifts. We report a case of early-onset, symptomatic hyponatremia leading to generalized seizure shortly after initiation of Aldactazide.

A 52-year-old woman with hypertension presented after experiencing a generalized tonic-clonic seizure at home. She had started Aldactazide (spironolactone + hydrochlorothiazide 25 mg daily) 3 days earlier, in addition to perindopril/amlodipine and captopril. Two weeks before symptom onset, her serum sodium level was 131 mmol/L. On admission to the intensive care unit, she was alert and hemodynamically stable, with a Glasgow Coma Scale score of 15. Laboratory evaluation revealed severe hyponatremia (115 mmol/L), hypokalemia (3.3 mmol/L; ionized 2.7 mmol/L), and hypochloremia (76 mmol/L). Lactate was transiently elevated at 8.3 mmol/L, consistent with postictal physiology. Renal, thyroid, and adrenal functions were normal. Brain CT and MRI showed no acute abnormalities. Controlled correction with 3% hypertonic saline resulted in progressive normalization of serum sodium (115 ⟶ 121 ⟶ 125 ⟶ 131 mmol/L) without overcorrection. The patient experienced complete neurological recovery and was transferred to the nephrology ward for continued monitoring. Aldactazide was discontinued.

This case demonstrates that TIH can develop rapidly in middle-aged individuals and may lead to life-threatening neurological complications, including seizures. Clinicians should closely monitor serum sodium during the early phase of thiazide-containing diuretic therapy, particularly when combination regimens such as Aldactazide are prescribed.