Abstract
BACKGROUND: 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. CASE PRESENTATION: 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. CONCLUSION: 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.