A Case of Thiazide-Induced Hyponatremia in an Elderly Patient

In the dawn of the modern era, hypertension is still prevalent globally. Regardless of age and gender, thiazide diuretics, calcium channel blockers, and renin-angiotensin inhibitors remain the first line of treatment. Drug-induced hyponatremia is a side effect of thiazide diuretics. At times, finding the cause of hyponatremia can be a challenging task due to the nonspecific clinical manifestations, and this can prove to be a hazard for serious morbidity and mortality. We report a case of a 75-year-old female patient with a BMI of 22.7 kg/m² and a past medical history of hypertension and hyperlipidemia who presented to our center with complaints of lethargy, weakness, and lightheadedness for five days. She was previously taking famotidine, atorvastatin, losartan, triamterene, and atenolol to manage her hypertension and hyperlipidemia. Her medication was changed to azilsartan-chlorthalidone, amlodipine, and carvedilol one week before presentation for better management of her blood pressure. Her electrolytes revealed sodium levels of 114 mmol/L, serum osmolality of 249 mOsmol/Kg (range 280 to 300 mOsmol/Kg), urine osmolality of 368 mOsmol/Kg, and urine sodium of 70 mmol/L (range 30 to 90 mmol/L). It was a new onset of hyponatremia, and her previous labs a month before the medication change were normal. The patient was discontinued on amlodipine, and the chlorthalidone component of azilsartan-chlorthalidone was discontinued. Her hydration was maintained with intravenous normal saline. The patient's health and symptoms improved after four days, along with an improvement in sodium levels. She was followed for two weeks and had been doing well. This case highlights the importance of taking a detailed history and examination, and taking into account drugs as a source of hyponatremia in elderly patients.