Case Presentation: A previously healthy 59-year-old male with newly-diagnosed hypertension and prediabetes presented to the emergency department following an unwitnessed syncopal episode on standing. He was found to have significant electrolyte abnormalities with critical values of potassium at 2.5, magnesium at 1.4, calcium at 6.3, phosphorus at 1.8, and a nonanion gap metabolic acidosis with bicarb of 19. His creatinine was at baseline at 0.66. His only medication was losartan 25mg started two days prior to presentation for hypertension. He symptoms included dizziness, lightheadedness, and urinary frequency since starting losartan. He did not take any additional medications and denied any recent illness, nausea, vomiting, diarrhea, and had no history of kidney disease. He endorsed drinking burdock root tea for a few weeks prior to admission to help with blood pressure control. Orthostatic vital signs were obtained and were unremarkable, and the only abnormality noted on physical exam was bradycardia. He was supplemented with intravenous potassium, magnesium, calcium and was given fluids and losartan was stopped. The electrolyte abnormalities and lightheadedness resolved and electrolytes stayed stable thereafter.
Discussion: This 59-year-old male on no other medications presented with syncopal episode and electrolyte derangements likely due to losartan which he recently started for hypertension. Losartan is an angiotensin receptor blocker prescribed for hypertension that works by inhibiting angiotensin II mediated vasopressin and catecholamine release, angiotensin II–induced vasoconstriction and the effects of aldosterone. It has most commonly been associated with hyperkalemia and acute kidney injury, but is also known to increase the excretion of sodium, potassium, chloride, magnesium, uric acid, calcium, and phosphorous in the urine, leading to a depletion in in these electrolytes, as seen in our patient. These excretory effects were found to be more significant in those with salt-restricted diets. These electrolyte abnormalities most likely were due to a rare adverse reaction to losartan as no other etiology was found, especially considering this patient reported increased urination after starting losartan. In regard to the herbal tea that he reported taking, burdock root has been used therapeutically for hundreds of years for its antioxidant and anti-inflammatory effects. Though a few case reports note symptoms of anticholinergic toxicity following consumption, this did not fit this patient’s presentation and unlikely that any of the included herbs could have produced such a profound effect on serum electrolytes. To our knowledge, there are no other published reports of profound electrolyte disturbances or syncopal episodes related to losartan use.
Conclusions: Losartan is widely considered to be a safe medication and is used widely in clinical practice for treating hypertension and heart failure. The most common lab abnormalities following initiation of losartan are hyperkalemia and an increase in creatinine. Less commonly, it is known to increase sodium, potassium, chloride, magnesium, uric acid, calcium, and phosphorus excretion and can cause hypokalemia, hypomagnesemia, hypophosphatemia, and hypocalcemia. Here we report a case of electrolyte depletion caused likely by losartan administration. Providers should be aware of these additional effects of losartan and monitor labs closely after starting it as it can be associated with high morbidity and mortality if missed.