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PubMed2001

Effect of acetazolamide on outward permeability of blood-retina barrier using differential vitreous flyorophotometry.

PURPOSE: To measure fluorescein (F) and fluorescein monoglucuronide (FG) concentrations in the vitreous and evaluate the effect of acetazolamide (AZM) on the outward permeability of the blood-retina barrier (BRB) using differential vitreous fluorophotometry (DVF). METHODS: DVF was performed 180 minutes after intravenous injection of AZM (5 mg/kg) and 50 mg of sodium fluorescein in six rabbits (AZM group). DVF also was performed in six rabbits injected intravenously with only 50 mg of sodium fluorescein (control group). The F/FG ratio was calculated based on the concentrations of F and FG obtained by DVF. DVF also was performed 180 minutes after 50 mg of intravenous injection of sodium fluorescein in five rabbits given probenecid (150 mg/kg) intraperitoneally (probenecid group). RESULTS: The average F/FG ratio was 0.36 +/- 0.17 (range, 0.22-0.66) in the AZM group, which was significantly smaller than the control value of 0.74 +/- 0.22 (range, 0.50-1.60). The average F/FG ratio at 180 minutes after injection was 1.51 +/- 0.46 (range, 0.94-2.00) in the probenecid group, which was significant higher (p < 0.05) than that of the AZM or control group. CONCLUSIONS: This study showed that the F/FG ratio might be a good indicator of the estimated outward permeability of the BRB using DVF and that AZM may accelerate the outward active transport function of the BRB.

Acetazolamide↗
PubMedDate not supplied

Influence of acetazolamide on AQP1 gene expression in testis and on sperm count/motility in epididymis of rats.

Acetazolamide (Ace) is a putative inhibitor of carbonic anhydrase (CA), an enzyme that catalyzes the equilibration of carbon dioxide and carbonic acid and plays a key role in HCO(3)(-) and water reabsorption and acid secretion. Aquaporins (AQPs) are channel-forming membrane glycoproteins that mediate water reabsorption by the renal tubules and other organs of mammals. AQP1 and CAII or CAIV share many common biological properties. Previous studies have shown that AQP1 and CA are located at the same sites in cells of the male reproductive tract. In the present study, Ace at a dose of 40 mg/kg/d x 14, administered per os, suppressed AQP1 gene expression and inhibited CA activity in rat testis. On day 7 of treatment the epididymal sperm motility was significantly reduced, while on day 14 a decrease in sperm count occurred. Ace caused a marked downregulation of AQP1 gene expression; significant suppression occurred on days 7 and 14. Moreover, CA activity was totally blocked throughout the treatment period. The present findings suggest that the reduction of rat sperm motility and count by Ace can be attributed to its capacity to downregulate AQP1 water channel gene expression.

Acetazolamide↗
PubMed1986

Cerebrovascular reactivity to acetazolamide in carotid artery disease. Enhancement of side-to-side CBF asymmetry indicates critically reduced perfusion pressure.

Cerebral blood flow (CBF), measured with a mobile 10 detector unit and non-invasive Xenon-133 technique, was investigated before and after cerebral vasodilation with acetazolamide (Diamox) in 78 patients prior to carotid endarterectomy. The change in side-to-side CBF asymmetry from baseline to Diamox study, the Diamox asymmetry enhancement, was compared with the intraoperatively measured cerebral perfusion pressures. Asymmetry enhancement exceeded the methodological variation in 14 patients, 13 of whom had a perfusion pressure below 65 mmHg. Insignificant asymmetry enhancement was found in 64 patients: 52 with unilateral and 12 with bilateral disease. Of these two and four patients, respectively, had perfusion pressures below 65 mmHg. Enhancement of CBF asymmetry following a potent cerebral vasodilator stimulus is a reliable predictor, in unilateral carotid artery disease, of critically reduced cerebral perfusion pressure.

Acetazolamide↗
PubMed1987

Evaluation of the regional cerebral vasodilatory capacity before carotid endarterectomy by the acetazolamide test.

To estimate the regional perfusion pressure and possibly the stump pressure during carotid endarterectomy, cerebral blood flow (CBF) measurements including a vasodilatory test were performed preoperatively. CBF was measured by 133Xe inhalation and emission tomography. An intravenous dose of 1g acetazolamide (Diamox) was used as cerebral vasodilator. Thirty-six patients with a clinical history of previous strokes (9 cases) or transient ischaemic attacks (27 cases) were studied. Nine of the patients showed occlusion of the contralateral internal carotid artery (ICA). The percent flow increase induced by Diamox in the ipsilateral hemisphere correlated to the ICA pressure was measured before clamping (n = 32, r = 0.55, p less than 0.001). In 12 of the 36 patients, Diamox caused a significant change in the flow distribution indicating a restricted regional vasodilatory capacity and a reduced regional perfusion pressure. In addition, these 12 patients showed a low stump pressure (less than 50 mmHg). However, 8 additional patients had uniform CBF increases at the Diamox test, but showed low stump pressures. It is concluded, that preoperative tests of the cerebral vasodilational capacity can be used to identify most patients with a low ICA pressure, and a substantial fraction of patients that will develop a low stump pressure upon ICA clamping during operation. In these patients with abnormal Diamox tests surgical reconstruction is particularly indicated, but, at the same time the perioperative risks are presumably highest in this group.

Acetazolamide↗
PubMed1995

Mapping the gene for acetazolamide responsive hereditary paryoxysmal cerebellar ataxia to chromosome 19p.

Acetazolamide responsive hereditary paroxysmal cerebellar ataxia (APCA) is a rare autosomal dominant disorder characterized by attacks of cerebellar ataxia and dysarthria with normal or near normal neurologic function between attacks. A genome-wide search using polymorphic di- and tri-nucleotide repeats was initiated and the APCA locus was found to be linked to the short arm of chromosome 19 in two large kindreds. The microsatellite marker UT705 was found to be linked to the APCA locus with two point analysis yielding a maximum lod score of 8.20 at theta max = 0.000 in a five generation pedigree. Linkage to this region was confirmed in a second kindred. The absence of known candidate genes in the region may necessitate a positional cloning approach in order to identify the gene for this disorder.

Acetazolamide↗
PubMed1987

Hereditary paroxysmal cerebellopathy: responsiveness to acetazolamide.

We describe kindred in which affected members had paroxysmal attacks of gait ataxia and other cerebellar symptoms. The mode of inheritance was autosomal dominant. Stress or emotion precipitated attacks. Examination between attacks revealed nystagmus but no other neurologic signs. After adulthood there was no progression of symptoms. Acetazolamide therapy successfully abolished the attacks.

Acetazolamide↗
PubMed1991

SPECT evaluation of brain perfusion reserve by the acetazolamide test using Tc-99m HMPAO.

This report describes a new approach to the evaluation of brain perfusion reserve using Tc-99m HMPAO SPECT. Consecutive brain Tc-99m HMPAO SPECT studies before and after acetazolamide (Diamox) administration were performed within 30 minutes on 19 patients with significant vascular occlusive lesions. Thirteen patients showed decreased perfusion reserve and four patients maintained perfusion reserve in the affected vascular territories after Diamox administration, providing additional information to baseline Tc-99m HMPAO SPECT in 17 (89%) patients. Although flow augmentation post-Diamox was underestimated, possibly due to the nonproportionality of Tc-99m HMPAO activity to true blood flow, significant changes in the brain perfusion pattern were both visually and quantitatively determined using an image subtraction technique. This consecutive Tc-99m HMPAO SPECT technique seems to be of practical use for the evaluation of brain perfusion reserve and for the improvement of the sensitivity of detecting pathologic areas.

Acetazolamide↗
PubMed1992

Acetazolamide effect on vascular response in areas with diaschisis as measured by Tc-99m HMPAO brain SPECT.

The effects of acetazolamide (Diamox) on vascular response were investigated in areas with intrahemispheric thalamic diaschisis and crossed cerebellar diaschisis using consecutive Tc-99m HMPAO brain SPECT studies before and after Diamox administration. All six patients with thalamic diaschisis and five of eight patients with crossed cerebellar diaschisis at baseline showed significantly augmented perfusion after Diamox administration in the affected thalamus and cerebellum compared with that in the contralateral unaffected areas. These results suggest more dilatation of the arterioles in areas with diaschisis after Diamox administration than in areas without diaschisis. Diamox may produce relative luxury perfusion in areas with diaschisis.

Acetazolamide↗
PubMed1988

The effect of acetazolamide on regional cerebral blood flow in normal human subjects as measured by single-photon emission computed tomography.

Regional cerebral blood flow (rCBF) was evaluated in 15 normal, healthy volunteer control subjects before and after the administration of 1 g acetazolamide (ACZ) using a rotating four-detector single-photon emission computed tomograph (SPECT). ACZ, a carbonic anhydrase inhibitor, is a cerebral vasodilator. RCBF values in mL/minute/100 g were derived within eight cortical regions of interest (ROI), and from the whole slice as an expression of whole brain blood flow (WBF). ROI/WBF ratios were established for each ROI in each of the 15 subjects for both pre-ACZ and post-ACZ studies. ACZ produced a 30% +/- 17% increase in WBF. Studies were done in random order, with nine subjects undergoing the post-ACZ study first, and six the pre-ACZ, or baseline, study first. Statistical analysis showed no significant difference in any ROI that might be caused by sequence of test procedures. Ratios were then examined to determine whether rCBF elevation was proportionate in all ROI in all subjects. No significant difference was found in any ROI except for the left parietal, for which marginally significant change was identified. Subjects also were examined for possible age and sex differences in ACZ response, and no differences were found.

Acetazolamide↗
PubMed1989

The effect of acetazolamide on regional cerebral blood flow in patients with Alzheimer's disease or stroke as measured by single-photon emission computed tomography.

Regional cerebral blood flow (rCBF) was assessed in 35 patients with possible or probable Alzheimer's disease (AD) and in 16 patients known to have had at least one stroke. Patients were evaluated before and after the administration of 1 g acetazolamide (ACZ) by means of a rotating four-detector single-photon emission computed tomograph (SPECT) and inhaled Xe-133. RCBF values in mL/minute/100 g were derived from eight cortical regions of interest (ROI), and from the whole transverse section as a measure of whole brain flow (WBF). ROI/WBF ratios were calculated for each ROI in paired determinations done before and 15 minutes after the administration of ACZ. Results were compared with those previously obtained in a study of 15 normal, healthy volunteer subjects. ROI/WBF ratios greater than 2 standard deviations (SD) below the mean for a given ROI in the normal group were regarded as probably abnormal, whereas ratios greater than 4 SD below the mean were considered definitely abnormal. After ACZ administration, the number of ROI greater than 2 SD below the normal mean decreased significantly in the AD group and was unchanged in the stroke patients. However, the number of ROI/WBF ratios greater than 4 SD below the normal mean fell in the AD group and rose in the stroke group, with the difference in behavior highly statistically significant. Thus, the response of low-flow areas to ACZ differs in AD and in stroke, which could be of ultimate diagnostic significance.

Acetazolamide↗
PubMed1995

Acetazolamide-induced vasodilation in the carotid vascular bed in healthy volunteers.

Acetazolamide (ACTZ) vasodilating properties are used for the assessment of cerebral vasodilatory reserve not only in cerebral pathology investigation, but also in clinical pharmacology studies. However, the kinetics of these vasodilating properties are not clearly established; moreover, the cerebral selectivity of ACTZ-induced vasodilation has not been demonstrated. To address these issues, we performed an ACTZ test in 9 healthy volunteers and measured noninvasively the effects exerted by the drug simultaneously on common carotid artery blood flow (CCABF), middle cerebral artery mean blood flow (BF) velocity (MV) (transcranial Doppler technique), and facial cutaneous BF (CutBF). The time of the peak increase in MV was variable, occurring between 20 and 40 min after ACTZ, and brief. In addition, simultaneous increases (with variable mean peak times) occurred in flows in the CCA (+11% at 20 min) and in its intracranial (+25% at 30 min) and extracranial (+134% at 50 min) branches. The first finding suggests that the cerebral effects of ACTZ should be measured repeatedly to detect in each individual subject the time of MV peak increase; the transcranial Doppler is particularly suitable for such an approach. The second finding suggests that, especially in patients, extracranial actions of ACTZ must be taken into account for estimation of the cerebral vasodilatory reserve.

Acetazolamide↗
PubMed2001

Cerebrovascular reactivity to acetazolamide in alert patients with cerebral infarction: usefulness of first-pass radionuclide angiography using 99m Tc-HMPAO in monitoring cerebral haemodynamics.

Cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) were studied in 75 patients with cerebral infarction. All patients were alert with the symptoms of hemiparesis and/or aphasia, and were divided into two groups: 42 patients had occlusion or stenosis of >75% at the internal carotid artery or main trunk of middle cerebral artery; and 33 patients did not. Hemispheric mean CBF was measured by performing first-pass radionuclide angiography using 99mTc-hexamethylpropylene amine oxime. CVR was measured as the percentage change from the baseline mean CBF value after the administration of 500 mg acetazolamide. The CVR in both groups was significantly impaired (5.2+/-6.3%, P<0.001 and 7.7+/-6.1%, P<0.01, respectively) compared with normal controls (14.7+/-3.3%), although the mean CBF was not significantly reduced compared with age-matched controls. In the 12 patients with unilateral carotid occlusion, five patients with good collateral flow via the anterior communicating artery showed preserved CVR (11.0+/-7.8%), but those without did not (1.6+/-7.0%). CVR is impaired in alert patients with cerebral infarction, although the mean CBF is not reduced, and good collateral flow via the anterior communicating artery in patients with carotid occlusion may be a sign of well-preserved haemodynamic status.

Acetazolamide↗
PubMed1985

Influence of advanced age on the disposition of acetazolamide.

The disposition kinetics of acetazolamide (AZ) has been studied in four young and four elderly healthy volunteers, each of whom received an intravenous bolus dose of 5 mg/kg. The concentration time profile of AZ was determined in plasma, plasma ultrafiltrate, erythrocytes and urine. While the mean area under unbound plasma concentration-time curves was 81% higher in elderly subjects, areas based on total drug concentrations were similar in both groups. The mean renal plasma clearance was similar in both groups. The mean renal plasma clearance was similar between young and old for total AZ, but was significantly lower in the elderly for unbound drug (8.88 ml min-1 kg-1 vs 15.7 ml min-1 kg-1). Renal clearance of unbound AZ correlated well with creatinine clearance (r = 0.846, P less than 0.01). Peak erythrocyte levels were 45% higher in the elderly group (37.2 micrograms/ml vs 25.3 micrograms/ml) and were paralleled by a 46% increase in the mean area under the erythrocyte concentration-time curve for this age group. The unbound fraction of AZ in plasma was significantly greater in elderly than younger subjects (6.9 vs 4.1%, P less than 0.05). Integrated AZ erythrocyte concentrations correlated positively with AZ free fraction in plasma and inversely with its unbound renal clearance. These observed differences in AZ disposition between elderly and young have served to clarify host factors which may importantly influence susceptibility to adverse effects.

Acetazolamide↗
PubMed1989

Differential effects of flurbiprofen and aspirin on acetazolamide disposition in humans.

The plasma concentration-time profile of acetazolamide (AZ) following an intravenous bolus dose (5 mg kg-1) was determined during control, aspirin and flurbiprofen (FLU) treatment periods. The unbound fraction of AZ in plasma increased three-fold in the presence of salicylate (SA) while, in contrast, FLU produced consistent, but statistically insignificant, increases in binding. SA caused a two-fold decrease in both unbound AZ renal clearance and apparent volume of distribution at steady-state, while FLU produced a small, but significant, increase only in the latter. The area under the concentration-time curve for AZ in erythrocytes was increased by about 40% during SA treatment while FLU had no effect. Our results suggest that on a pharmacokinetic basis FLU may be a safer nonsteroidal anti-inflammatory drug (NSAID) to co-administer with AZ.

Acetazolamide↗
PubMed1995

Effects of acetazolamide on the sleep apnea syndrome and its therapeutic mechanism.

Twenty male patients with sleep apnea syndrome were treated with acetazolamide (AZM), a carbonic anhydrase inhibitor. In 14 of the patient a significant decrease was found in the number of apnea, apnea index and % apnea time (percentage of time spent with apnea to the total sleep time) with improvement in sleep structure, clinical symptoms, such as insomnia, daytime excessive sleepiness and snoring. A significant decrease was also observed in arterial blood pH and HCO-3 in the 14 improved patients. On the other hand, no improvement occurred in the parameters of sleep apnea and sleep with AZM in the remaining six patients. Moreover, metabolic acidosis and an improvement in arterial blood gases did not occur with AZM in the six patients.

Acetazolamide↗
PubMed1994

The influence of acetazolamide and amlodipine on the intracellular sodium content of rat proximal tubular cells.

1. This investigation set out to use 23Na n.m.r. spectroscopy to measure changes in intracellular levels of sodium in isolated suspensions of rat proximal tubules. The effects of temperature, an inhibitor of the sodium pump and known natriuretic drugs on intracellular sodium content of such tubular preparations were measured and compared with calcium channel antagonists where action at this level is unclear. 2. Rat kidneys were perfused with collagenase, roughly chopped, subjected to mechanical dispersion and washed to remove all traces of the enzyme. The proximal tubules were then purified and concentrated by Percoll density gradient centrifugation and then resuspended in buffer containing dysprosium tripolyphosphate shift reagent. 3. Distinct peaks corresponding to intracellular and extracellular sodium signals were observed when the tubules were placed into the n.m.r. spectrometer. As the temperature of the suspension rose to 37 degrees C, there was an exponential decrease in sodium content, with a decay constant of 0.15 +/- 0.02 min-1, which reached a stable level within 20 to 25 min. Addition of ouabain, 10(-3) M, resulted in a significant (P < 0.01) 30% increase in intracellular sodium content within 5 min which peaked at 70% 20 min later. Although acetazolamide (10(-3) M) significantly (P < 0.01) increased intracellular sodium content by 45%, amlodipine (10(-4) M) had no effect. 4. These data show that changes in the activity of the Na+/K+/ATPase have a considerable influence on the intracellular levels of sodium in proximal tubule cells. Inhibition of carbonic anhydrase activity resulted in a rise in intracellular sodium content which is compatible with its action to reduce the turnover rate of the Na+/(HCO3-)3 symporter. The lack of effect of amlodipine was consistent with the suggestion that it does not have a direct action on the sodium handling processes at the level of the proximal tubule.

Acetazolamide↗