Losartan Has No Effect on High Altitude Diuresis or Acute Mountain Sickness in Well-Acclimatizing Individuals

Abstract

has no effect on high altitude diuresis or acute mountain sickness in well-acclimatizing individuals. High Alt Med Biol. 22:96-101, 2021. Introduction: The diuretic response that occurs on ascent to altitude is associated with suppression of aldosterone. We speculated that losartan, an angiotensin II receptor blocker, might further reduce aldosterone activity thereby enhancing the diuresis. Materials and Methods: Twenty subjects (paired for angiotensin converting enzyme genotypes [II:ID:DD] gender and age) were randomized, on a double-blind basis, to either daily losartan, 100 mg, or placebo. During 7 days of motorized ascent from 2,850 to 5,035 m, collections of 24-hour urine output were measured daily with samples taken for sodium (Na + ) and potassium (K + ) concentrations. In addition, measurements were made of blood gases and aldosterone concentrations. Results: During the main ascent, there were similar progressive increases in 24-hour urine volumes in placebo and losartan groups with no change in Na + or K + excretion. There were negative correlations between mean 24-hour urine volumes and PaO 2 (r = -0.97, p < 0.03), and the diuretic response and acute mountain sickness scores at 5,053 m (r = -0.51, p < 0.03). There were no significant changes in aldosterone concentrations measured at baseline and at our high point on day 6 within or between the losartan and placebo groups. Conclusion:The high altitude diuretic response was not increased by losartan indicating aldosterone activity was suppressed in individuals on placebo who were acclimatizing well to altitude.

Wilderness Medical Society Clinical Practice Guidelines for the Prevention, Diagnosis, and Treatment of Acute Altitude Illness: 2024 Update

“…Their utility in prevention of altitude illness has not been properly studied, so they should not be substituted for other established preventive measures described in these guidelines. Multiple studies have sought to determine whether other agents, including angiotensin receptor antagonists, 68 antioxidants, 69 iron, 70 dietary nitrates, 71 leukotriene receptor blockers, 72,73 phosphodiesterase inhibitors, 74 salicylic acid, 75 spironolactone, 76 and sumatriptan, 77 can prevent AMS, but the current state of evidence does not support their use. “Forced hydration” or “overhydration” have never been shown to prevent altitude illness and might increase the risk of hyponatremia; however, maintenance of adequate hydration is important because symptoms of dehydration can mimic those of AMS.…”