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PubMed1989

Acetazolamide blood concentrations are excessive in the elderly: propensity for acidosis and relationship to renal function.

Elderly glaucoma patients are often treated with acetazolamide, a carbonic anhydrase inhibitor with clearance dependent on renal function. A high incidence of metabolic acidosis and other adverse effects have been noted among these patients but the reasons for this have not been explained. We hypothesized that commonly used doses of acetazolamide among the elderly result in excessive blood concentrations and that these concentrations are related to acid-base disturbances. We measured steady-state acetazolamide levels in plasma, plasma ultrafiltrate (unbound), and erythrocytes among 12 elderly subjects (79.2 +/- 7.6 years old). Mean plasma (18.9 +/- 10.9 micrograms/mL) and ultrafiltrate concentrations (1.0 +/- 0.7 microgram/mL) exceeded the therapeutic range (plasma 5-10 micrograms/mL; ultrafiltrate 0.25-0.50 microgram/mL) for glaucoma control by two fold and were elevated in 75% of subjects. Plasma and ultrafiltrate acetazolamide levels significantly correlated with the dose adjusted for creatinine clearance (r = 0.91, P less than 0.001; r = 0.89, P less than 0.001, respectively). Acidotic subjects (serum total carbon dioxide less than or equal to 22 mEq/L) tended to have higher plasma, ultrafiltrate, and erythrocyte acetazolamide levels compared with nonacidotic subjects. Serum total carbon dioxide levels were significantly correlated with erythrocyte acetazolamide concentrations (r = -0.75, P = 0.03). The ratio of erythrocyte acetazolamide concentration to creatinine clearance separated acidotic from nonacidotic subjects (P less than 0.01). These findings suggest that some of the adverse effects of acetazolamide can be avoided by reducing the dose to compensate for age-related reductions in renal drug clearance.

Acetazolamide↗

PubMed1998

Pharmacokinetics and pharmacodynamics of acetazolamide in patients with transient intraocular pressure elevation.

OBJECTIVE: To characterize the pharmacokinetics and pharmacodynamics of acetazolamide in patients with transient intraocular pressure (IOP) elevation and to provide individual patients with the optimal dosage regimen for this drug. METHODS: We studied 17 patients with transient IOP elevation, who were given 62.5-500 mg acetazolamide orally as single or repetitive doses. Plasma acetazolamide concentration and IOP were measured at approximately 1, 3, 5, and 9 h after the last acetazolamide administration. Pharmacokinetics and pharmacodynamics were analyzed by nonlinear mixed-effect modeling using the program NONMEM. RESULTS: The plasma concentration profile of acetazolamide was characterized by a one-compartment model with first-order absorption. The apparent oral clearance was related to the creatine clearance (CCR) which was estimated by the Cockcroft and Gault equation, as follows: 0.0468 x CCR1 x h(-1). The estimated apparent oral volume of distribution, first-order absorption rate constant, and absorption lag time were 0.231 l x kg(-1), 0.821 x h(-1), and 0.497 h, respectively. IOP after oral acetazolamide administration was characterized by an Emax model. The maximal effect in lowering the IOP (Emax) was 7.2 mmHg, and the concentration corresponding to 50% of the maximal effect (EC50) was 1.64 microg x ml(-1). As 70% of Emax was achieved at a plasma concentration of 4 microg x ml(-1), this concentration was considered satisfactory for lowering IOP. The recommended dosage was calculated so that the minimum plasma concentration at steady state exceeded this target concentration; 250 mg t.i.d., 125 mg t.i.d., 125 mg b.i.d., and 125 mg once daily for the patients with CCR values of 70, 50, 30, and 10 ml min(-1), respectively. CONCLUSION: Measuring plasma concentrations of acetazolamide and subsequent pharmacokinetic and pharmacodynamic analyses are useful for estimating its concentration-dependent effectiveness in lowering the IOP in individual patients. The dosage regimen presented in this study is expected to improve the benefits of acetazolamide pharmacotherapy in most elderly patients with transient rises in IOP following intraocular surgery.

Acetazolamide↗

PubMed1985

Ulcer formation and cytoprotection by acetazolamide.

Acetazolamide, a carbonic anhydrase inhibitor, was administered orally and subcutaneously to rats. Acetazolamide increased the gastric ulcerogenicity of indomethacin, but inhibited gastric ulcers produced by acidified aspirin. When administered alone to fasted rats, it did not produce gastric ulcers. Acetazolamide was also cytoprotective for the stomach (it reduced dose dependently the number of gastric necrotic lesions caused by absolute ethanol given orally) and for the small intestine (it prevented dose dependently intestinal lesions produced by administration of a high dose of indomethacin). Acetazolamide did not prevent the antiulcer effect of PGE2 (against aspirin-induced ulcers) nor the cytoprotective effect of 16,16-dimethyl PGE2 (against ethanol-induced gastric lesions). The degree of gastric cytoprotection increased with time after a single administration of acetazolamide; the optimal effect occurred 60 and 90 min after oral and subcutaneous administration, respectively. Pretreatment with indomethacin completely prevented the cytoprotective effect of acetazolamide; this suggests that the cytoprotective effect may be mediated by endogenous release of prostaglandins by the stomach. All the effects of acetazolamide reported here were observed after either oral or subcutaneous administration. The mechanism by which acetazolamide influences ulcer formation and is cytoprotective is unknown.

16,16-Dimethylprostaglandin E2↗

PubMed1996

Effect of acetazolamide on cough induced by low-chloride-ion solutions in normal subjects: comparison with furosemide.

BACKGROUND: The antitussive activity of inhaled furosemide has been attributed to its blocking effect on the Na(+)-2Cl(-)-K+ cotransporter. It is likely that the antitussive activity of inhaled diuretics is more complex because amiloride, a diuretic that has no effect on the Na(+)-2Cl(-)-K+ cotransporter, also shows a significant effect against cough induced by low-chloride-ion solutions. Apart from pharmacokinetics of inhaled diuretics, this activity could also depend on the inhibition of carbonic anhydrase. OBJECTIVES: We therefore studied the effect of inhaled acetazolamide, a selective inhibitor of carbonic anhydrase activity, on cough induced by the inhalation of different chloride ion solutions in a group of normal subjects. This was compared with the antitussive effect of furosemide. In addition, we attempted to determine whether the effect of acetazolamide is dose-dependent. METHODS: Cough challenge consisted of consecutive inhalations of four solutions having decreasing concentrations of chloride ions (150, 75, 37.5 and 0 mmol/L). Nine normal subjects underwent the cough challenge 5 minutes after the inhalation of saline placebo, acetazolamide (500 mg), and furosemide (30 mg) according to a randomized, double-blind study design. A group of six subjects were challenged according to the same procedure and study design, after the inhalation of saline placebo and of two doses of acetazolamide (250 mg and 500 mg). RESULTS: Inhaled acetazolamide significantly reduced cough response to 37.5 and 0 mmol/L chloride solutions compared with placebo (p less than 0.015 and p less than 0.015, respectively). Furosemide showed a similar protective effect (p less than 0.015 and p less than 0.025, respectively). Acetazolamide provided a significantly better protective effect than furosemide (p less than 0.025 and p less than 0.015, respectively). The antitussive activity of the two doses of acetazolamide was not statistically different. CONCLUSION: These results demonstrate that inhaled acetazolamide, a selective inhibitor of carbonic anhydrase, attenuates cough induced by low-chloride-ion solutions in normal subjects. At the applied doses, its antitussive activity is slightly greater than furosemide. This finding suggests that the inhibition of carbonic anhydrase activity is likely involved in modulating changes caused by absence of a chloride ion in the airway microenvironment of human beings.

Acetazolamide↗

PubMed1996

A randomized, masked, cross-over trial of acetazolamide for cystoid macular edema in patients with uveitis.

PURPOSE: To study the effect of acetazolamide on cystoid macular edema in patients with uveitis. METHODS: Forty patients with chronic intermediate, posterior, or panuveitis associated cystoid macular edema were randomized into a masked, cross-over trial comparing acetazolamide versus placebo. Patients received an initial 4-week course of either acetazolamide or placebo (course A) followed by a 4-week washout period. They then received a 4-week course of the opposite study medication (course B). Primary endpoints included area of cystoid macular edema measured on late-phase views of fluorescein angiography and visual acuity. RESULTS: Thirty-seven patients completed the trial and were available for analysis; 17 (46%) were randomized to receive acetazolamide and 20 (54%) to receive placebo during course A. Acetazolamide resulted in a 0.5-disc area (25%) decrease in cystoid macular edema over that of placebo (P = 0.01; estimated treatment effect = -0.5 disc areas; 95% confidence interval, -0.9 to -0.1). However, there was no statistically significant effect of acetazolamide on visual acuity (P = 0.61; estimated treatment effect = 0.6 letters; 95% confidence interval, -2 to 3). CONCLUSIONS: A 4-week course of acetazolamide therapy results in a statistically significant but small decrease in cystoid macular edema in patients with chronic uveitis, and does not improve visual acuity. In contrast to previous studies in the literature, acetazolamide may have a more limited clinical benefit in patients with long-standing cystoid macular edema associated with chronic uveitis.

Acetazolamide↗

PubMed1998

Combination of systemic acetazolamide and topical dorzolamide in reducing intraocular pressure and aqueous humor formation.

OBJECTIVE: The study aimed to determine whether topical dorzolamide and systemic acetazolamide have an additive effect on intraocular pressure (IOP) and aqueous humor formation (AHF). DESIGN: This was a prospective, open-label, two-protocol clinical study. PARTICIPANTS: Sixteen patients with ocular hypertension or with primary open-angle glaucoma were studied. INTERVENTION: Baseline AHF was measured by computerized fluorophotometry and IOP by pneumatonometry without antiglaucoma therapy. In the first protocol, dorzolamide was randomized to one eye (N = 10) and IOP and AHF measurements were repeated. One week later, having used dorzolamide in one eye three times daily, patients had measurements performed before and after the single administration of oral acetazolamide 250 mg. In the second protocol, having used acetazolamide 250 mg four times daily for 4 to 7 days (N = 6), patients had measurements performed before and after a single drop of dorzolamide was instilled randomly into one eye. The patient continued acetazolamide and unilateral dorzolamide for 4 to 7 more days and returned for IOP and AHF measurements. MAIN OUTCOME MEASURES: Intraocular pressure and AHF were measured in treated and contralateral control eyes. RESULTS: In the first protocol, IOP (mmHg +/- standard deviation) was significantly (P = 0.02) lower in the dorzolamide (16.3 +/- 2.6) than in the contralateral control (19.9 +/- 2.9) eyes. Aqueous humor formation (microliter/minute +/- standard deviation) also was lower (P = 0.02) in dorzolamide eyes (1.79 +/- 0.4 vs. 2.33 +/- 0.5). After oral acetazolamide 250 mg, IOP was unchanged in dorzolamide eyes (17.6 +/- 2.0 preacetazolamide vs. 17.9 +/- 2.0 postacetazolamide), whereas it was reduced (P = 0.003) in control eyes (20.5 +/- 2.2 preacetazolamide vs. 16.9 +/- 2.3 postacetazolamide). Aqueous humor formation was reduced in control eyes (2.31 +/- 0.8 preacetazolamide vs. 1.73 +/- 0.6 postacetazolamide; P = 0.005) but not in dorzolamide-treated eyes (1.56 +/- 0.45 preacetazolamide vs. 1.77 +/- 0.39 postacetazolamide). In the second protocol, acetazolamide 250 mg four times daily symmetrically reduced IOP and AHF in both eyes. After single-drop dorzolamide in one eye, IOP and AHF did not change significantly. After 4 to 7 days of acetazolamide and unilateral dorzolamide, IOP and AHF remained reduced to a similar level in dorzolamide and control eyes not receiving topical therapy. CONCLUSION: Topical dorzolamide and oral acetazolamide, in the concentrations and doses used in this study, are not additive. Either drug alone results in maximum reduction in IOP and AHF. Concomitant glaucoma therapy of a topical and systemic carbonic anhydrase inhibitor is not warranted.

Acetazolamide↗

PubMed2003

The effect of acetazolamide on the changes of cerebral blood flow and oxygen metabolism during visual stimulation.

Acetazolamide, a carbonic anhydrase inhibitor, has an anticonvulsant effect which may result from a decrease in the efficacy of synaptic transmission due to a decrease of pH. Our previous study showed that acetazolamide induced a significant increase in global and regional cerebral blood flow (CBF), but caused no significant change in the cerebral metabolic rate of oxygen (CMRO(2)). To investigate the effect of acetazolamide on the responses of CBF and CMRO(2) during neural stimulation, we used positron emission tomography to measure CBF and CMRO(2) in six normal volunteers at the fixation-only baseline visual state and during visual stimulation before and after administration of 1 g of acetazolamide. Visual stimulation induced a significant increase in CBF (33%) in the visual cortex compared with baseline values, but caused no significant change in CMRO(2), while no significant change in global CBF or CMRO(2) was found. During visual stimulation after acetazolamide administration, both global and visual cortical CBF and CMRO(2) showed similar changes compared with the respective baseline values (37 and 65% increases in CBF and 8 and 16% decreases in CMRO(2), respectively). When corrected by the global values, the magnitudes of the CBF and CMRO(2) responses to visual stimulation after acetazolamide administration were less than those before (20% vs 38% in CBF and -9% vs 3% in CMRO(2)). Considering our previous observation that the effect of acetazolamide was similar throughout cerebral cortical regions, we suggest that acetazolamide decreases the responses of both CBF and CMRO(2) during visual stimulation, which indicates that this drug may affect neuronal excitability.

Acetazolamide↗

PubMed1998

A comparison of the efficacy and tolerability of dorzolamide and acetazolamide as adjunctive therapy to timolol. Oral to Topical CAI Study Group.

PURPOSE: To compare the efficacy and tolerability of dorzolamide to acetazolamide. METHODS: Following a timolol and acetazolamide run-in, 105 patients with elevated intraocular pressure (IOP) were randomized to dorzolamide or acetazolamide, in addition to timolol, for 12 weeks. RESULTS: More patients receiving acetazolamide discontinued due to clinical adverse experiences than patients receiving dorzolamide; 13 (25%) vs. 1 (2%); p<0.001. The prevalence of systemic adverse experiences for the dorzolamide group dropped by 50% by Week 12, but remained unchanged for the acetazolamide group, as compared to baseline; p<0.001. Ocular burning/stinging was more common in the dorzolamide group (21% vs. 0%; p<0.001). The mean trough IOP at Day 1 and Week 12 were 20.5 mmHg and 21.8 mmHg for the dorzolamide group, and 20.4 mmHg and 20.5 mmHg for the acetazolamide group. The mean peak IOP at Dayl and Week 12 were 18.9 mmHg and 20.0 mmHg for the dorzolamide group, and 18.7 mmHg and 18.6 mmHg for the acetazolamide group. CONCLUSIONS: Mean IOP was slightly lower (by approximately 1 mmHg) with acetazolamide, while dorzolamide demonstrated much better tolerability.

Acetazolamide↗

PubMed1999

Relationship between acetazolamide blood concentration and its side effects in glaucomatous patients.

Although acetazolamide, a carbonic anhydrase inhibitor, has an effect of lowering intraocular pressure, a number of side effects have been reported. Therefore, we investigated the relationship between the concentration of acetazolamide and its side effects, including plasma electrolyte imbalance. This study was conducted on 23 glaucomatous patients who received repeated doses of oral acetazolamide for one week or more. The concentrations of total and unbound plasma acetazolamide, as well as in the whole blood from the patients, were measured by high-performance liquid chromatography. The serum creatinine concentration, electrolyte concentrations, and adverse reactions were monitored. We found that plasma concentrations of chloride ion after repeated doses became higher than the normal range. This chloride ion concentration significantly correlated with the acetazolamide concentration in the erythrocytes, but not with the plasma concentration. The patients with erythrocyte acetazolamide concentration more than 20 microg/ml had higher incidences of the side effects. Periodical monitoring of erythrocyte acetazolamide concentration and plasma chloride ion can be easily and safely applied to elderly glaucomatous patients treated with acetazolamide for long periods to prevent overdosage and side effects.

Acetazolamide↗

PubMed2004

Effects on aqueous flow of dorzolamide combined with either timolol or acetazolamide.

PURPOSE: To determine the effect on aqueous flow of topical dorzolamide 2%, topical timolol 0.5%, or oral acetazolamide 250 mg when used alone or when dorzolamide is combined with either timolol or acetazolamide. METHODS: In 30 patients with ocular hypertension, aqueous flow and intraocular pressure (IOP) were determined at baseline and on the following combinations of drugs in a crossover design: (1) vehicle alone, (2) dorzolamide alone, (3) acetazolamide alone, (4) timolol alone, (5) dorzolamide + acetazolamide, and (6) dorzolamide + timolol. Treated eyes were compared with control eyes and comparisons were made between treatments. RESULTS: Compared with baseline, significant (P < 0.04) IOP reductions in the order of efficacy were: dorzolamide + timolol > dorzolamide + acetazolamide = acetazolamide = timolol > dorzolamide. Aqueous flow was reduced more by dorzolamide + timolol than by each drug alone (P < 0.04) and more by dorzolamide + acetazolamide than by dorzolamide alone (P < 0.04). CONCLUSION: The combination of dorzolamide and timolol demonstrated significant aqueous flow additivity and had greater IOP efficacy than the combination of dorzolamide and acetazolamide.

Acetazolamide↗

PubMed1984

Antipsychotic and prophylactic effects of acetazolamide (Diamox) on atypical psychosis.

We investigated the antipsychotic and prophylactic effects of acetazolamide (Diamox) on atypical psychosis. Acetazolamide was given to 30 patients: Type I, puberal periodic psychosis, a psychosis whose onset occurs during the period of puberty and which appears repetitively with psychosis-like condition at about the same interval as the menstrual cycle (6 cases); Type II, a) presenile atypical psychosis which initially appears in patients in their 20s or 30s accompanied by manic-depressive cycles and shows acute confusional and dreamy states in the presenile period, incurable cases (7), b) atypical psychosis, in the narrow sense, cases which show acute hallucination, delusion, confusional and dreamy states accompanied by affective symptoms (8 cases); Type III, repetitively the atypical manic and depressive states, and atypical manic-depressive psychosis, and transient changes in consciousness, refractory cases (2); Type IV, atypical schizophrenia, which is considered to be schizophrenia but shows the abnormalities in electroencephalogram and emotional disorders (7 cases). Among these cases, some extent of the therapeutic effects of acetazolamide (500-1,000 mg/day) was obtained in about 70%. The high therapeutic effects were particularly observed in Types I, II and III. It was less effective against atypical schizophrenia. Acetazolamide showed the effectiveness in 10 cases out of 13 cases to which lithium carbonate and carbamazepine were ineffective. The high therapeutic effects of acetazolamide were shown in the cases whose symptoms were aggravated at the interval of the menstrual cycle. No correlation was observed between the electroencephalographic abnormalities and the therapeutic effects. In addition, the prophylactic effects of acetazolamide on the periodic crisis were observed in 9 cases. From these results, acetazolamide was considered to have the antipsychotic and prophylactic effects on atypical psychosis. Since side effects due to acetazolamide were rarely observed, the present drug was considered to have a high safety margin.

Acetazolamide↗

PubMed2004

Randomised, double blind, placebo controlled comparison of ginkgo biloba and acetazolamide for prevention of acute mountain sickness among Himalayan trekkers: the prevention of high altitude illness trial (PHAIT).

OBJECTIVE: To evaluate the efficacy of ginkgo biloba, acetazolamide, and their combination as prophylaxis against acute mountain sickness. DESIGN: Prospective, double blind, randomised, placebo controlled trial. SETTING: Approach to Mount Everest base camp in the Nepal Himalayas at 4280 m or 4358 m and study end point at 4928 m during October and November 2002. PARTICIPANTS: 614 healthy western trekkers (487 completed the trial) assigned to receive ginkgo, acetazolamide, combined acetazolamide and ginkgo, or placebo, initially taking at least three or four doses before continued ascent. MAIN OUTCOME MEASURES: Incidence measured by Lake Louise acute mountain sickness score > or = 3 with headache and one other symptom. Secondary outcome measures included blood oxygen content, severity of syndrome (Lake Louise scores > or = 5), incidence of headache, and severity of headache. RESULTS: Ginkgo was not significantly different from placebo for any outcome; however participants in the acetazolamide group showed significant levels of protection. The incidence of acute mountain sickness was 34% for placebo, 12% for acetazolamide (odds ratio 3.76, 95% confidence interval 1.91 to 7.39, number needed to treat 4), 35% for ginkgo (0.95, 0.56 to 1.62), and 14% for combined ginkgo and acetazolamide (3.04, 1.62 to 5.69). The proportion of patients with increased severity of acute mountain sickness was 18% for placebo, 3% for acetazoalmide (6.46, 2.15 to 19.40, number needed to treat 7), 18% for ginkgo (1, 0.52 to 1.90), and 7% for combined ginkgo and acetazolamide (2.95, 1.30 to 6.70). CONCLUSIONS: When compared with placebo, ginkgo is not effective at preventing acute mountain sickness. Acetazolamide 250 mg twice daily afforded robust protection against symptoms of acute mountain sickness.

Acetazolamide↗

PubMed1983

Bicarbonaturic effect of acetazolamide in the dog: the influence of graded volume expansion.

Studies were performed in anesthetized dogs to characterize the effect of a progressive volume expansion on the acetazolamide-induced bicarbonaturia. A closed system with urine reinfusion was used in all these experiments. In normovolemic dogs, 24% of the filtered bicarbonate was excreted into the urine while this value reached 62% when a 10% expansion was superimposed on a continuous infusion of acetazolamide. When a single dose of acetazolamide was given, fractional bicarbonate excretion increased from 21% in normovolemic dogs to 46% during 10% expansion. Without acetazolamide administration, 13% of the filtered bicarbonate was excreted during a 10% expansion. The continuous infusion of acetazolamide in normovolemic dogs increased fractional bicarbonate excretion in a progressive fashion, from 25 to 40%. This study shows that an acute volume expansion potentiates markedly the bicarbonaturic effect of acetazolamide, fractional bicarbonate excretion exceeding by far the simple additive effect of acetazolamide and expansion. We speculate that volume expansion might prevent a compensatory rise in acetazolamide-insensitive bicarbonate reabsorption in sites other than the superficial proximal convoluted tubules.

Acetazolamide↗

PubMed1990

Effects of acetazolamide on metabolic and respiratory responses to exercise at maximal O2 uptake.

Changes in blood gases, ions, lactate, pH, hemoglobin, blood temperature, total body metabolism, and muscle metabolites were measured before and during exercise (except muscle), at fatigue, and during recovery in normal and acetazolamide-treated horses to test the hypothesis that an acetazolamide-induced acidosis would compromise the metabolism of the horse exercising at maximal O2 uptake. Acetazolamide-treated horses had a 13-mmol/l base deficit at rest, higher arterial Po2 at rest and during exercise, higher arterial and mixed venous Pco2 during exercise, and a 48-s reduction in run time. Arterial pH was lower during exercise but not in recovery after acetazolamide. Blood temperature responses were unaffected by acetazolamide administration. O2 uptake was similar during exercise and recovery after acetazolamide treatment, whereas CO2 production was lower during exercise. Muscle [glycogen] and pH were lower at rest, whereas heart rate, muscle pH and [lactate], and plasma [lactate] and [K+] were lower and plasma [Cl-] higher following exercise after acetazolamide treatment. These data demonstrate that acetazolamide treatment aggravates the CO2 retention and acidosis occurring in the horse during heavy exercise. This could negatively affect muscle metabolism and exercise capacity.

Acetazolamide↗

PubMedDate not supplied

Mechanism of acetazolamide-induced rise in renal vascular resistance assessed in the dog whole kidney.

The reduction in renal blood flow (RBF) and glomerular filtration rate (GFR) observed after the administration of the carbonic anhydrase inhibitors acetazolamide and benzolamide had been explained as due to activation of the tubuloglomerular feedback mechanism. If correct, pharmacologic blockade of this pathway should prevent the development of renal vasoconstriction with the carbonic anhydrase inhibitors. Thus, the current study evaluates in the dog whole kidney the effect of acetazolamide (20 mg/kg body weight) in the presence or absence of furosemide (5 mg/kg body weight), a drug which blocks the tubuloglomerular feedback. Acetazolamide resulted in a large increase in urinary bicarbonate excretion accompanied by a significant reduction in GFR (16%) and RBF (18%). By contrast with the effects of acetazolamide, furosemide did not alter GFR and increased RBF. In addition, the loop diuretic induced a large chloruresis without changes in urinary bicarbonate excretion. The infusion of acetazolamide in furosemide-treated dogs resulted in a significant increment in renal bicarbonate excretion and in a significant reduction in the levels of both GFR (28%) and RBF (13%). Therefore, furosemide pretreatment did not block the effects of acetazolamide on renal hemodynamic parameters. Consequently, the acetazolamide-induced reduction in both GFR and RBF cannot be accounted for by changes in chloride levels in the juxtaglomerular region due to enhanced salt transport in the macula densa/distal nephron. The increased renal vascular resistance observed with acetazolamide might occur by either a direct effect of this agent on the renal circulation or as a result of changes in intrarenal pressure secondary to the inhibition of proximal fluid reabsorption.

Acetazolamide↗

PubMed1990

Effect of acetazolamide on cerebral blood flow velocity and CO2 elimination in normotensive and hypotensive newborn piglets.

The objectives of this study were to measure the effect of acetazolamide on cerebral circulation, pulmonary elimination of CO2, and cerebrovascular response to hypotension in newborn piglets. Eighteen anaesthetized newborn piglets were studied. A fontanelle was surgically created and the cerebral blood flow velocity (CBFV) in an intracranial artery measured by a computerized Doppler system. In 8 piglets, 30 ml/kg of blood was removed to produce hypotension before the administration of acetazolamide. Acetazolamide (50 mg/kg i.v.) given to normotensive piglets consistently produced a large increase in CBFV (median 45% by 5 min) with no change in mean arterial blood pressure or heart rate. The rise in CBFV was negatively correlated with the starting partial pressure of CO2 in arterial blood. Within 1 min of administration of acetazolamide, the end-expiratory CO2 pressure started to fall (mean fall 1.4 kPa), and the partial pressure of CO2 in the arterial blood started to rise (mean rise 2.0 kPa), despite the controlled ventilation being unchanged. Acetazolamide had no effect on CBFV in the hypotensive piglet. It seems likely that acetazolamide produces cerebral vasodilatation by inhibiting the elimination of CO2. In hypotension, there is maximal cerebral vasodilatation, and acetazolamide cannot increase CBFV further. The interference of acetazolamide with CO2 elimination could seriously limit its use in the treatment of hydrocephalus in preterm infants.

Acetazolamide↗

PubMed1990

Vascular effects of acetazolamide on the choroid plexus.

Decreases in production of cerebrospinal fluid (CSF) after administration of acetazolamide have been attributed in part to constriction of blood vessels of the choroid plexus. The first goal of the present study was to examine effects of acetazolamide on blood flow to the choroid plexus. We measured blood flow (microspheres) and the production of CSF (ventriculo-cisternal perfusion) in anesthetized rabbits. Under control conditions, blood flow to the choroid plexus was 466 +/- 34 (mean +/- S.E.) ml min-1 100 g-1 and CSF production was 9.4 +/- 0.9 microliters min-1. Acetazolamide (25 mg kg-1 i.v.) decreased production of CSF by 55 +/- 5% despite a 2-fold increase in blood flow to the choroid plexus. The second goal of this study was to examine the role of hypercapnia, which occurs after administration of acetazolamide, in producing increases in blood flow. In animals in which hypercapnia was prevented by increases in ventilation, acetazolamide produced a similar increase in blood flow to the choroid plexus. We conclude that acetazolamide decreases the production of CSF but, in contrast to predictions based on studies in vitro, acetazolamide produces a marked increase in blood flow to the choroid plexus. Thus, changes in blood flow to the choroid plexus and production of CSF are uncoupled after administration of acetazolamide.

Acetazolamide↗

PubMed1994

Gastric mucosal protection by acetazolamide in rats. Roles of prostaglandins, sulfhydryls, and gastric motility.

The aim of this study was to test the hypothesis that protective effect of subcutaneous acetazolamide, a carbonic anhydrase inhibitor, against ethanol-induced gastric mucosal damage is dependent on indomethacin- or iodoacetamide-sensitive mechanisms. In addition we studied the effects of acetazolamide on gastric motility and the influence of indomethacin and iodoacetamide on this parameter. Indomethacin (30 mg/kg) or iodoacetamide (100 ag/kg) was administered subcutaneously in doses that previously had been demonstrated to inhibit endogenous prostaglandins synthesis and gastric mucosal sulfhydryls respectively. At 30 min after these or control subcutaneous pretreatment, the rats were given subcutaneous acetazolamide or vehicle. Thirty min later 96% ethanol was administered orally and the rats were sacrificed 60 min after ethanol administration. The lesions of the gastric glandular mucosa were measured in length and width and expressed in square millimeters. Gastric motility was recorded by a balloon method. The results showed that neither indomethacin nor iodoacetamide aggravated ethanol-induced gastric mucosal damage. The protective effect of subcutaneous acetazolamide was suppressed by pretreatment with indomethacin but not with that of iodoacetamide. Acetazolamide inhibited gastric motility in a dose-dependent fashion. The inhibited gastric motility induced by acetazolamide was reversed by indomethacin but not by iodoacetamide. A highly significant relationship was found between the inhibitory effect of acetazolamide on the motor activity and the mucosal lesions (r +/- 0.8777, P < 0.01). We conclude that the mechanism mediating subcutaneous acetazolamide protection against 96% ethanolinduced gastric mucosal lesions is dependent on indomethacin- and independent of iodoacetamide sensitive mechanisms.

Acetazolamide↗