Effects of acetazolamide on cerebral blood flow and brain tissue oxygenation

Abstract

Summary Oral administration of 1 g of acetazolamide to 8 normal subjects studied at sea level and in normoxia caused an acute increase in cerebral blood flow (CBF). During the subsequent prolonged oral treatment with 1 g of acetazolamide daily, CBF returned to normal within 2 days. The alveolar CO2 tension decreased gradually to 70% of the control value, indicating hyperventilation. At sea level hyperventilation will not increase brain oxygenation significantly in normal man, as the arterial oxygen content only increases minimally, while CBF is unchanged. At high altitude the beneficial effects of acetazolamide on the symptoms of acute mountain sickness may well be due to an improved oxygen supply to the brain, as hyperventilation will, at the low ambient PO2, cause a significant increase of the arterial oxygen content, while CBF presumably is unaffected by the drug. During hypoxia at high altitude the overall effect of prolonged acetazolamide treatment may thus be equivalent to a descent by several hundred metres.

Cerebrovascular reactivity in hypertensive patients: A transcranial doppler study

“…8,9,12 Several studies have proved that acetazolamide dilates the cerebral vessels. 8,9,[12][13][14][15][16]24,25 The only known effect of acetazolamide is the reversible inhibition of carbonic anhydrase. 26 Acetazolamide increases CBF, although the mechanism by which it does so has not yet been explained.…”

“…8,9,[12][13][14][15] One gram of this drug given intravenously increases CBF by more than 50% in 20 minutes. 16 In the present study, our aim was to determine whether TCD is sensitive enough for assessing changes in vasoreactivity in patients with hypertension and for correlating such changes with the duration of hypertension.…”

Vasodilatory Capacity of the Cerebral Vasculature in Patients with Carotid Artery Stenosis

“…Acetazolamide is a reversible inhibitor of the enzyme carbonic anhydrase, and though the exact mechanism is unknown, the vasodilatory effect on the vasculature of the brain is ascribed to carbonic acidosis. 20,21 We show that the vasodilatory effect of acetazolamide can be assessed by measuring changes in arterial diameter throughout the vasculature of the brain. Other challenges used to measure the presence or degree of hemodynamic impairment rely predominantly on stimulating CO 2 -reactive arterioles by increasing the CO 2 concentration through inhalation, breath-holding, or hyperventilation.…”

Acetazolamide as a vasodilatory stimulus in cerebrovascular diseases and in conditions affecting the cerebral vasculature

“…(1983) reported 75% increase in the carotid artery flow velocity after intravenous infusion of 500 mg AZ. However, the same oral dose did not alter CBF (Lassen et al. , 1987).…”