Ocular complications of neurological therapy

Treatments used for several neurological conditions may adversely affect the eye. Vigabatrin-related retinal toxicity leads to a visual field defect. Optic neuropathy may result from ethambutol and isoniazid, and from radiation therapy. Posterior subcapsular cataract is associated with systemic corticosteroids. Transient refractive error changes may follow treatment with acetazolamide or topiramate, and corneal deposits and keratitis with amandatine. Intraocular pressure can be elevated in susceptible individuals by anticholinergic drugs, including oxybutynin, tolterodine, benzhexol, propantheline, atropine and amitriptyline, and also by systemic corticosteroids and by topiramate. Nystagmus, diplopia and extraocular muscle palsies can occur with antiepileptic drugs, particularly phenytoin and carbamazepine. Ocular neuromyotonia can follow parasellar radiation. Congenital ocular malformations can result from in utero exposure to maternally prescribed sodium valproate, phenytoin and carbamazepine. Neurologists must be aware of potential ocular toxicity of these drugs, and appropriately monitor for potential adverse events.

Acetazolamide, a carbonic anhydrase inhibitor, reverses inflammation-induced thermal hyperalgesia in rats

Inflammatory pain is linked to reduction in tissue pH. Tissue proton generation is mainly mediated by carbonic anhydrases (CAs). We therefore hypothesized that inhibition of CAs with acetazolamide (ACTZ) increases the tissue pH and reverses inflammation-induced pain. CAs are also present in the central nervous system and control anion concentrations. Furthermore, ACTZ has direct effects on ion channels involved in nociception. In the current study, responses to heat and mechanical stimuli (von Frey filaments) of the paw were assessed before and after carrageenan-induced muscle inflammation and after treatment with ACTZ in rats. ACTZ was administered systemically, locally, or intrathecally 24 h after the induction of inflammation. In separate studies, pH was measured in the inflamed and noninflamed muscles and after administration of ACTZ. Carrageenan injection to the gastrocnemius muscle produced heat hyperalgesia and mechanical allodynia of the paw. Systemic ACTZ reversed the heat hyperalgesia but not mechanical allodynia. Similarly, injections of ACTZ into the inflamed muscle or intrathecally reversed the heat hyperalgesia but not mechanical allodynia. Surprisingly, the pH in the inflamed muscle was not reduced compared with noninflamed muscle. Thus, the current data do not support our hypothesis that ACTZ reduces inflammatory hyperalgesia by raising the reduced pH in muscle. Although the possibility of pH changes and the role of CAs in the microenvironment cannot be ruled out, the mechanism of ACTZ-induced antihyperalgesia is not clear from this study. It is possible that the inhibition of ion channels and/or the inhibition of spinally located CAs contribute to the observed antihyperalgesia.

Transient Neurologic Deficit After Acetazolamide Challenge for Computed Tomography Perfusion Imaging

A case of transient neurologic deficit associated with the acetazolamide challenge conducted in conjunction with dynamic enhanced computed tomography (CT) perfusion imaging for the evaluation of cerebral hemodynamic impairment is reported in a patient with known cerebrovascular steno-occlusive disease. Combining the acetazolamide challenge with dynamic CT perfusion provides a rapid and widely available technique to assess cerebrovascular reactivity; however, one must be cognizant of this serious potential adverse response.

Einfluss von ProstaglandinF2 α-Analoga und Karboanhydraseinhibitoren auf die zentrale Hornhautdicke - eine Querschnittsstudie an 403 Augen*

BACKGROUND

Histological changes of, in particular, collagen and extracellular matrix after administration of topical prostaglandin F(2alpha)(PGF (2alpha)) analogues have been reported. In view of this observation, we investigated the influence of PGF(2alpha) analogues on the central corneal thickness.

PATIENTS AND METHODS

In a non-randomized, controlled, cross-sectional study, 403 eyes from 208 consecutive patients were examined: 149 eyes (normals/controls) and 79 with ocular hypertension (OHT), 119 eyes with primary open angle glaucoma (POAG) and 56 eyes with normal tension glaucoma (NTG). One experienced ophthalmologist measured the central corneal thickness (CCT) using ultrasound pachymetry (Tomey AL-2000, sequence of 5 measurements with an SD < 3 microm). The central corneal power was measured with the Zeiss keratometer. Depending on the topical treatment, the patients were classified into 4 groups: A) PGF(2alpha) analogues (n = 78), B) carbonic anhydrase inhibitors (n = 26), C) combination of PGF (2)(alpha) analogues and carbonic anhydrase inhibitors (n = 41), D) none of these drugs (n = 258). T tests and multiple linear regression analyses were used for statistical analysis.

RESULTS

CCT was decreased significantly (p < 0.01 each) in eyes treated with PGF(2alpha) analogues (group A: 529 +/- 34 microM), in comparison with the untreated and non-glaucomatous eyes (part of group D: 542 +/- 35 microM, n = 148), untreated glaucomatous/OHT eyes (part of group D: 563 +/- 37 microM, n = 110), eyes treated with carbonic anhydrase inhibitors (group B: 561 +/- 32 microm) and eyes with a topical application of both PGF (2)(alpha) analogues and carbonic anhydrase inhibitors (group C: 555 +/- 48 microM. No correlation was found between CCT and diagnosis (OHT, POAG, NTG, control), gender, central corneal power, and intraocular pressure in a multivariate analysis.

CONCLUSIONS

The present findings suggest that the topical application of prostaglandin F(2alpha) analogues onto the cornea reduces the central corneal thickness significantly. These changes might be attributed to effects of PGF(2alpha) analogues on the extracellular matrix of the corneal stroma via upregulation of matrix metalloproteinases. In clinical practice, corneal thinning under local PGF (2)(alpha) analogue treatment could result in underestimation of intraocular pressure levels as measured by applanation tonometry.

[Acute confusional syndrome associated with obstructive sleep apnea aggravated by acidosis secondary to oral acetazolamide treatment]

Acute confusional syndrome, or delirium, is a transitory mental state characterized by the fluctuating alteration of awareness and attention levels. We present the case of a patient with acute confusional syndrome associated with obstructive sleep apnea syndrome (OSAS) aggravated by metabolic acidosis induced by oral acetazolamide treatment.A 70-year-old man with no history of neurological disease was referred with a clinical picture consistent with acute confusional syndrome presenting between midnight and dawn. During the admission examination infectious, toxic, and neurologic causes, or those related to metabolic or heart disease were ruled out. Arterial blood gases measured during one of the nighttime episodes of acute confusional syndrome showed mild hypoxia and hypercapnia with mixed acidosis. Signs and symptoms suggestive of OSAS had been developing over the months prior to admission, with snoring, sleep apnea, and moderate daytime drowsiness. Polysomnography demonstrated severe OSAS with an apnea-hypopnea index of 38. Mean arterial oxygen saturation was 83%; time oxygen saturation remained below 90% was 44%. The attending physician ordered the withdrawal of oral acetazolamide, which was considered the cause of the metabolic component of acidosis. Treatment with continuous positive airway pressure was initiated at 9 cm H2O, after a titration polysomnographic study. The patient continued to improve.OSAS, for which very effective treatment is available, should be included among diseases that may trigger acute confusional syndrome.

Presumed "sulfa allergy" in patients with intracranial hypertension treated with acetazolamide or furosemide: cross-reactivity, myth or reality?

PURPOSE

To determine whether acetazolamide or furosemide produce allergic cross-reactions in patients with self-reported "sulfa allergy."

DESIGN

Retrospective case series.

METHODS

A retrospective review included patients with intracranial hypertension and a self-reported sulfa allergy treated with either acetazolamide or furosemide seen at the University of Iowa Hospitals and Clinics from 1972 to 2003. All presumed medication-related side effects were collected, including both predictable adverse effects (for example, paresthesias, fatigue) and unpredictable adverse reactions (for example, cutaneous fixed eruptions, urticaria, Stevens-Johnson syndrome, toxic epidermal necrolysis, angioedema, anaphylaxis).

RESULTS

We reviewed 363 charts. Of these, 329 patients (91%) were excluded. Of the remaining 34 cases that did report a so-called sulfa allergy, 13 (38%) received acetazolamide alone, 7 (21%) received furosemide alone, and 14 (41%) received both acetazolamide and furosemide. Of the 27 patients who received acetazolamide, 10 (37%) had no documented allergic cross-reaction to sulfa, and 2 (7%) cases had urticaria. The remaining 15 (56%) of acetazolamide-treated patients experienced predictable adverse reactions for this drug (for example, paresthesias). No patient experienced a severe allergic cross-reaction to sulfa. Of 21 patients who received furosemide, no unpredictable adverse reactions or allergic cross-reactions to sulfa were noted.

CONCLUSIONS

We find little clinical or pharmacological evidence to suggest that a self-reported sulfa allergy is likely to produce a life-threatening cross-reaction with acetazolamide or furosemide. These medications should be considered for intracranial hypertension if the risk-to-benefit ratio warrants their use.

[Carbonic anhydrase inhibitors and calcium phosphate stones]

We report a case of a 33 years old female with a history of paroxystic hemidystonia treated by acetazolamide, a carbonic anhydrase inhibitor (CAI), and who developed two years after the initiation of this treatment bilateral radio-opaque stones. Laboratory tests revealed a hyperchloremic acidosis, an elevated urinary pH, a hypercalciuria, a severe hypocitraturia and numerous granulations of amorphous carbonated calcium phosphates and brushite crystals on urinary microscopic examination, the whole suggests a diagnosis of acetazolamide-induced nephrolithiasis. We discuss in this article the lithogenetic process and the usual composition of the stones induced by CAI, and specific risk factors for developing drug-induced lithiasis which should be taken into consideration when prescribing long-term drug regimens.

Metabolic changes after H(2) 15O-positron emission tomography with acetazolamide in a patient with moyamoya disease: case report and review of previous cases

Perioperative ischemic complications not directly related to surgery require special attention in patients with moyamoya disease; positron emission tomography (H(2) 15O-PET) and single-photon emission computed tomography have been considered indispensable for evaluating pre- and postsurgical cerebral hemodynamics. The clinical records of 14 patients with moyamoya disease who underwent 26 extracranial-intracranial bypass operations were reviewed with special reference to perisurgical complications. One patient developed multiple postoperative ischemic infarctions and died of ischemic brain edema. The history of this patient with prolonged acidosis is analyzed, and the role of metabolic changes induced by H(2) 15O-PET with acetazolamide challenge is reviewed. Seven (77.8%) of nine patients operated on within 48 hours after H(2) 15O-PET with acetazolamide (group 1) developed metabolic acidosis, whereas only three (17.6%) of 17 patients operated on >48 hours (group 2) after the examination had intraoperative pH of <7.35. In group 1, the mean intraoperative pH was 7.328, which was significantly lower than the mean pH of 7.393 (P <.0001) in group 2. After H(2) 15O-PET with acetazolamide challenge, patients must be carefully observed concerning acidosis and volume state. We recommend at least 48 hours between examination and surgery for patients with moyamoya disease so that their conditions can stabilize. Furthermore, special care should be taken to avoid additional perioperative risk factors such as hypotension, hypocapnia, hypercapnia, and hypovolemia.

Treatment of sporadic hemiplegic migraine with calcium-channel blocker verapamil

Gene mutations within the P/Q type neuronal calcium channel in familial hemiplegic migraine (FHM) suggest a therapeutic role for calcium-channel blockade. The authors have previously reported abortive therapy of FHM with IV verapamil. Here the authors describe four cases of sporadic hemiplegic migraine (SHM) responsive to verapamil, administered either orally or IV. The findings indicate that verapamil is effective therapy for both SHM and FHM.

Acetazolamide-induced muscle weakness in hypokalemic periodic paralysis

A 46-year-old man with hypokalemic periodic paralysis (HypoPP) and diabetes mellitus (DM) had worsened muscle weakness after acetazolamide (ACZ) treatment. During the paralytic episode, serum potassium levels were reduced, and serum chloride and insulin levels were increased. The data suggested proximal renal tubular acidosis due to ACZ. We determined arterial-venous concentrations of potassium, insulin and glucose across the forearm. Venous potassium levels were markedly reduced. ACZ is thought to potentiate potassium uptake into muscles. Hyperinsulinemia and DM could contribute to ACZ-induced exacerbation in our patient. We should pay more attention to ACZ-treated HypoPP patients with hyperinsulinemia and DM.

Tolerability and efficacy of dorzolamide versus acetazolamide added to timolol

PURPOSE

Evaluate the safety and efficacy of dorzolamide versus acetazolamide when added to once daily 0.5% timolol maleate ophthalmic gel forming solution (timolol gel).

METHODS

This was a randomized, double-masked, multicenter, active-controlled, parallel group study of 215 patients with open-angle glaucoma or ocular hypertension. Following a two-week treatment period with timolol gel, patients with IOP > or = 22 mm Hg and who tolerated one week of acetazolamide 250-mg q.i.d. either were randomized to acetazolamide or dorzolamide 2% three times daily for 12 weeks.

RESULTS

In 155 randomized patients (dorzolamide, N = 80, acetazolamide, N = 75), compared to the dorzolamide, acetazolamide had a statistically greater number of systemic adverse events (dorzolamide 50%, acetazolamide 75%, p = 0.001), adverse events associated with carbonic anhydrase inhibitor (CAI) therapy (dorzolamide 26%, acetazolamide 53%, p < 0.001) and discontinuations due to CAI adverse experiences (dorzolamide 8%, acetazolamide 24%, p = 0.007). Intent to treat analysis found that changes from baseline in IOP were similar at both troughs (dorzolamide 1.4 +/- 0.46 mm Hg, acetazolamide 0.8 +/- 0.47 mm Hg, p = 0.386). However, per-protocol analysis found statistically improved pressure control with acetazolamide (0.1 +/- 0.42 mm Hg) compared to dorzolamide (1.9 +/- 0.43 mm Hg) (p = 0.009).

CONCLUSIONS

This study found a greater incidence of systemic and CAI adverse experiences and discontinuations due to acetazolamide compared to dorzolamide.

Long-term effectiveness and side effects of acetazolamide as an adjunct to other anticonvulsants in the treatment of refractory epilepsies

The long-term effectiveness of acetazolamide (AZA) and its side effects, especially the formation of renal calculi, were investigated in a prospective study when AZA was used as an adjunct to other antiepileptic drugs in the treatment of refractory epilepsies. The subjects comprised 37 patients aged from 1 to 17 years (mean age, 8 years and 1 month) whose seizures were hard to control with the use of two or more drugs among sodium valproate, carbamazepine and clonazepam. Thirty-two of the 37 patients were complicated with mental retardation. A daily dose of 10mg/kg of AZA was first administered and then the dosage was increased up to 20mg/kg based on the clinical response and side effects. The maintenance daily dosage of AZA (12.2+/-4.2mg/kg) produced a steady-state plasma concentration of 6.2+/-4.5 microg/ml. Among the 37 patients, complete seizure control for more than 3 years was obtained in four patients. Although there were no significant differences, all of the four patients were classified as having symptomatic localization-related epilepsies. Seizures recurred in five after complete remission for at least 6 months, and six showed >50% decrease in seizure frequency for more than 6 months after the introduction of AZA. Twenty-eight patients, who were taking AZA for 10 months to 14 years (mean, 6 years and 5 months), were examined for the formation of renal calculi. None of them showed evidence of renal calculi. This study reinforces the idea that AZA may be a useful adjunct drug in selected patients with refractory symptomatic localization-related epilepsies.

Pathogenic mechanism, prophylaxis, and therapy of symptomatic acidosis induced by acetazolamide

BACKGROUND

Acetazolamide, a noncompetitive carbonic anhydrase inhibitor, can produce symptomatic acidosis and bone marrow suppression by a mechanism that is still unknown. This presentation occurs in the elderly, patients with renal or liver failure, people with diabetes, and newborns. The objective of this study was to understand the pathogenic mechanism of these adverse effects and to propose a possible prophylaxis and therapy.

METHODS

Four human clinical cases were studied, and one animal experiment was performed. Four preterm newborns with posthemorrhagic ventricular dilation developed severe metabolic acidosis after treatment with acetazolamide. The acidosis suddenly disappeared after a packed red blood cell transfusion. Metabolic studies were performed in one patient and in newborn guinea pigs treated with 200 mg/kg acetazolamide.

RESULTS

Acetazolamide can produce severe lactic acidosis with an increased lactate-to-pyruvate ratio, ketosis with a low beta-hydroxybutyrate-to-acetoacetate ratio, and a urinary organic acid profile typical of pyruvate carboxylase deficiency. The acquired enzymatic injury resulting from the inhibition of mitochondrial carbonic anhydrase V that provides bicarbonate to pyruvate carboxylase can produce tricarboxylic acid cycle damage. We demonstrate that the dramatic disappearance of metabolic acidosis and normalizing metabolism after blood transfusion were due to the citrate contained in the packed red blood cell bag. This hypothesis was confirmed by animal experimentation. We argue that the metabolic disorder and bone marrow suppression may be related.

CONCLUSION

We demonstrate how acetazolamide can lead to symptomatic metabolic acidosis and probably to bone marrow suppression. We suggest citrate as a possible prophylaxis and treatment for these adverse reactions.

Efficacy and tolerability of acetazolamide in migraine prophylaxis: a randomised placebo-controlled trial

BACKGROUND

Familial hemiplegic migraine and episodic ataxia type 2 (EA2) are allelic disorders with distinct types of mutations in the CACNA1A gene. EA2 attacks are remarkably sensitive to acetazolamide, a carbonic anhydrase inhibitor. The effectiveness of acetazolamide in migraine prophylaxis is unknown.

OBJECTIVES

To evaluate the efficacy and the tolerability of acetazolamide in migraine prophylaxis.

METHODS

We compared daily oral 500 mg acetazolamide and placebo in patients with migraine in a multicentre, double-blind, randomised trial of 12 weeks duration after a run-in period of 4 weeks without treatment. Frequency of attacks at the last trial period of 4 weeks was the primary efficacy criterion. Secondary efficacy criteria were the frequency of attacks per 4 weeks, the severity and duration of attacks, the number of hours with migraine as well as the number of responders with more than 50% reduction in attack frequency.

RESULTS

53 patients had been enrolled when the study was prematurely stopped because of a high number of withdrawals (34%), primarily linked to acetazolamide related side effects. Considering the primary and secondary efficacy criteria, among the 53 included patients (27 in the placebo group and 26 in the acetazolamide group), no difference between the 2 study groups could be demonstrated. The most frequent adverse events related to acetazolamide were paresthesias and asthenia.

CONCLUSIONS

In this trial, migraine sufferers poorly tolerated acetazolamide given in an oral dose of 500 mg daily. No obvious prophylactic beneficial effect of acetazolamide appeared on migraine attacks.

Randomized, controlled trial of acetazolamide and furosemide in posthemorrhagic ventricular dilation in infancy: follow-up at 1 year

OBJECTIVE

Posthemorrhagic ventricular dilation (PHVD) is a complication of intraventricular hemorrhage in preterm infants and is associated with a high risk of long-term disability. Furosemide and acetazolamide are used widely in the treatment of PHVD in the hope of avoiding the need for placement of a ventriculoperitoneal shunt, but these drugs have not been evaluated in a controlled trial. This article reports a multicenter, randomized, controlled trial designed to test the hypothesis that these drugs would reduce the rate of shunt placement (or death) and increase survival to 1 year of age without disability.

METHODS

Between 1992 and 1996, 177 infants who were less than 3 months past term and had ventricular width >4 mm above the 97th centile following intraventricular hemorrhage were assigned randomly to either standard therapy or standard therapy plus drug therapy with acetazolamide (100 mg/kg/d) plus furosemide (1 mg/kg/d). Infants who were enrolled in the trial had a median gestational age of 28.6 weeks and were enrolled at a mean postnatal age of 3.6 weeks. Forty-four percent were reported to have a cerebral parenchymal lesion on ultrasound scan at randomization. The primary outcome measure of death or shunt placement (known in all but 1 infant) occurred in 56 of 88 infants who were allocated to drug plus standard therapy compared with 46 of 88 who were allocated to standard therapy. The risk ratio was 1.23 (95% confidence interval: 0.95-1.59). Neurodevelopmental outcome information at a corrected age of 1 year (known in all but 3 of 149 surviving infants) included disability or neuromotor impairment in 54 of 67 infants (81%) who were allocated to drug plus standard therapy and 52 of 69 infants (66%) who were allocated to standard therapy. Seventy-two of 85 infants (85%) who were allocated to drug therapy either died or were disabled or impaired at 1 year compared with 62 of 89 infants (70%) who were treated with standard therapy (risk ratio: 1.22; 95% confidence interval: 1.03-1.4376). The excess risk of these adverse outcomes was greater among infants who did not have a cerebral parenchymal lesion seen on ultrasound examination at trial entry.

CONCLUSIONS

These results suggest that the use of acetazolamide and furosemide in preterm infants with PHVD is ineffective in decreasing the rate of shunt placement and is associated with increased neurologic morbidity. This treatment therefore cannot be recommended.

Sodium channel inactivation defects are associated with acetazolamide-exacerbated hypokalemic periodic paralysis

A novel mutation in a family with hypokalemic periodic paralysis is described. The mutation R672S is located in the voltage sensor segment S4 of domain II in the SCN4A gene encoding the human skeletal muscle voltage-gated sodium channel. Functional expression of the R672S channels in human embryonic kidney 293 cells revealed a small but significant hyperpolarizing shift in the steady-state fast inactivation, and a dramatic enhancement in channel slow inactivation. These two defects are mainly due to a slow recovery of the mutant channels from fast and/or slow inactivation. Our data may help explain the mechanism underlying hypokalemic periodic paralysis and the patient's worsening from acetazolamide.

[Therapeutic use of potassium citrate]

Therapeutic indications of potassium citrate include: 1. Oxaluric renal stone disease and some cases of uric acid stone disease. Prevention of stone formation in patients with renal polycystic disease. Prevention of stone relapse after ESWL or lithotomy; 2. Distal renal tubular acidosis complicated by hypercalciuria, mainly in children. 3. Renal hypercalciuria and hyperoxaluria. 4. Prevention of renal complications at the time of glaucoma treatment with acetazolamide. 5. Potassium supplementation during treatment of hypertension. Potassium citrate is usually contraindicated in the case of: 1. Urinary tract infection. 2. Struvite renal stone disease. 3. Hyperpotassemia and advanced chronic renal failure. 4. Peptic ulcer or gastritis. 5. Gastrointestinal bleeding. 6. Disorders of coagulation, crural varices. 7. Metabolic alkalosis. Potassium citrate, when used at therapeutic doses, is to be considered as quite safe. The average daily dose even if admitted as a single dose day engages 60-75% of free renal capacity for potassium excretion. Physiologic and therapeutic citrate concentration in urine exceeds much those available for other inhibitors. The therapeutic dose does not induce any significant changes in any biochemical or endocrine parameter of blood except mild transient metabolic alkalosis. The decrease of urine calcium and increase in oxalate calcium phosphate excretion is observed. In hypo-cytriaturic patients the response to therapeutic dose of citrate is smaller. One-year remission of stone disease is observed in 70-75% cases.

Transient renal tubular acidosis in a neonate following transplacental acetazolamide

Renal tubular acidosis (RTA) was observed in a preterm boy shortly after birth. His mother had glaucoma and had been treated during pregnancy with oral acetazolamide, a carbonic anhydrase inhibitor. When RTA developed, acetazolamide was detected in his serum demonstrating transplacental acetazolamide passage.

Acute mountain sickness score and hypoxemia

BACKGROUND

Hypoxemia is the immediate consequence of hyobaric hypoxia, which is the crucial starting mechanism of acute mountain sickness (AMS). The AMS is generally a benign and self-limiting condition which can be prevented by gradual ascent. However, ascent rates recommended for prophylaxis of AMS are far slower than those attempted during military operations and by climbers.

OBJECTIVE

The current study was carried out to quantify the relationship between AMS and hypoxemia alongwith evaluating the benefits of acetazolamide-dexamethasone chemoprophylaxis during acute ascent.

SUBJECTS AND METHODS

Twenty-four low lander male adults (age mean +/- SE 27.8 +/- 1.24 years) were selected. They were grouped in a double-blind fashion into four groups and each group (n = 6) received placebo (multivitamin) or acetazolamide (250 mg) or dexamethasone (4 mg) or a combined regimen of the two drugs twice daily for 5 days, commencing 24 hours before ascent. The volunteers reached the altitude of 4578 meters within a span of one day. Their AMS symptoms were recorded on modified environmental symptoms questionnaire (ESQ), after 24 and 72 hours of ascent. Arterial PO2, SO2 and PCO2 were measured by GEMSTAT blood-gas analyzer (Mallincrodt-USA).

RESULTS

The ESQ, AMS-C (cerebral) and AMS-R (respiratory) scores of combined therapy group were significantly lower as compared to the other groups on the symptom rating scale. The significant finding amongst the volunteers taking acetazolamide was mild to moderate diuresis whereas severity of headache was markedly less in dexamethasone group. The commonest feature of combined therapy was that none of the volunteers complained of headache, dysponea, irritability and more than mild disturbance of sleep. The ESQ scores of volunteers were inversely correlated to PaO2 and SaO2 after 24 hours of ascent to 4578 meters.

CONCLUSION

The study concludes that severity of AMS is closely related to hypoxemia and combination therapy of acetazolamide-dexamethasone may be effective in preventing AMS.

Benign intracranial hypertension: correlation of cerebral blood flow with disease severity

Benign intracranial hypertension (BIH) is characterized by symptoms and signs of raised intracranial pressure in the absence of an intracranial mass lesion, infection or hydrocephalus. The purpose of this study was to evaluate the effect of disease severity on cerebral blood flow in patients with BIH on acetazolamide therapy.

METHODS

11 patients (nine females, two males; mean age 30.5 years; range 22-29 years) with BIH were studied. All patients underwent CT and MRI scanning which were normal. The CSF pressure of all patients was above 200 mm H2O. All patients were under treatment with acetazolamide (1 g/day). Disease severity was determined by visual field examination and by clinical symptoms. Five patients were categorized into mild to moderate BIH (group I) and six patients had severe BIH (group II). All patients underwent perfusion brain SPECT with 740 MBq of Tc-99m-HMPAO.

RESULTS

Brain perfusion abnormalities were observed in six of the 11 patients. One out of five patients in group I (20%) and five out of six patients (83%) in group II, had abnormal SPECT findings (P<0.04). In four patients of group II the left parietal lobe was involved and another patient had a right occipital abnormality. The single patient from group I with SPECT abnormalities demonstrated focal decreased perfusion in the left temporal area and decreased perfusion in the left caudate nucleus.

CONCLUSION

Patients with severe degree of BIH have a higher incidence of cerebral perfusion abnormalities. This group may have an increased risk of cerebrovascular complications. The continuous administration of acetazolamide which affects the vascular autoreactivity may contribute to the regional hypoperfusion. Further studies are recommended to evaluate the natural course of disease versus iatrogenic treatment effects.

Inhibition of carbonic anhydrase in the lens does not induce myopia in cynomolgus monkeys

Refraction was measured in eyes of cynomolgus (Macaca irus) monkeys, before and during continuous intravenous infusion of large doses of the carbonic anhydrase (CA) inhibitors acetazolamide and ethoxzolamide. No changes of refraction were seen. Therefore, inhibition of CA in lens, cornea and retina does not appear to be the cause of the transient myopia and associated symptoms, occasionally observed in patients treated with CA inhibitors.

New alternative agents in essential tremor therapy: double-blind placebo-controlled study of alprazolam and acetazolamide

Propranolol and primidone are widely used, effective agents in essential tremor although they are not tolerated by all patients. In the present study, the effectiveness of alprazolam, a triazole analog of benzodiazapine class, and acetazolamide, a carbonic anhydrase inhibitor, were investigated as symptomatic treatments for essential tremor. We studied 22 patients with essential tremor in a double-blind, cross-over, placebo-controlled design. The patients received in random order alprazolam, acetazolamide, primidone and placebo for four weeks, each separated by a two-week washout period. The study demonstrated that alprazolam was superior to placebo and equipotent to primidone, whereas there was no statistically significant difference between acetazolamide and placebo. The mean effective daily dose of alprazolam was 0.75 mg and there was not any troublesome side effect reported by the patients on alprazolam. Alprazolam can be used as an alternative agent in elderly essential tremor patients who can not tolerate primidone or propranolol.

[Fatal anaphylactic reaction after oral acetazolamide (diamox) for glaucoma]

A woman aged 66 was prescribed acetazolamide (Diamox) in the outpatient clinic because of glaucoma. She went into irreversible anaphylactic shock with massive pulmonary oedema, probably due to a cross reaction in sulphonamide allergy. Before prescribing acetazolamide, the physician should inquire about sulphonamide allergy because of the related chemical structure of the substances. Such an allergy should be regarded as a contraindication.

Paroxysmal dystonia induced by exercise and acetazolamide

We report a case of a 40-year-old woman with dystonic attacks precipitated by slight exercise. Episodes lasted 2-5 min and were not precipitated by sudden movements or by being startled, drinking alcohol, coffee or tea, or by stress. Secondary dystonia was ruled out and brain magnetic resonance imaging (MRI) was unremarkable. Routine and video electroencephalogram (EEG) during and between attacks were normal. Acetazolamide greatly worsened her condition, whereas gabapentin [1-(aminomethyl) cyclohexaneacetic acid] treatment markedly reduced the frequency and severity of the episodes.

The dose-response relationship of acetazolamide on the cerebral blood flow in normal subjects

BACKGROUND

Acetazolamide (AA) is used to determine the cerebral vasoreactivity (CVR). To investigate whether the usually applied standard dose of 1 g intravenously will guarantee stable test conditions, the dose-response relationship of AA on cerebral blood flow (CBF) and cerebral blood flow velocity (CBFV) in normal subjects was determined.

METHODS

In 59 healthy volunteers, rCBF was measured with a (133)Xenon inhalation device, and CBFV of the middle cerebral artery (MCA) by transcranial Doppler sonography. The first CBF measurement was taken at rest, the second 15 min after application of AA at a dosage of 5, 10, 13, 15 and 18 mg/kg of body weight, respectively. The CBFV (n = 52) of the middle cerebral artery on the side of the better temporal window was taken 25 min after application of AA 13 mg/kg. In order to determine the side effects of AA, statements of an additional 172 patients were included.

RESULTS

A significant dosage dependence of AA on the CBF (fast flow and initial slope index) exists between 5 and 18 mg/kg intravenously. After AA 13 mg/kg, the fast flow increases from 70.8 +/- 10.8 to 110.1 +/- 13.5 ml/100 g/min, the initial slope index from 46.5 +/- 5.4 to 62.8 +/- 5.8, and the CBFV from 51.5 +/- 8.5 to 85.4 +/- 14.2 cm/s. The CVR of CBF and CBFV ascertained that way shows an age dependence equivalent to the situation at rest. Severity and frequency of side effects are dosage-dependent, significantly in part, but reversible without exception.

CONCLUSION

For the determination of CVR of CBF with AA, a dosage related to body weight is required. The usually applied standard dose of 1 g intravenously is not sufficient for standardized test conditions. For evaluation of the results obtained, the apparent age dependence of CVR must be taken into account. Because of the severity of side effects occurring at a higher dose, an AA dosage of 13 mg/kg intravenously is recommended.

Acetazolamide-induced Gerstmann syndrome

Acute confusion induced by acetazolamide is a well known adverse drug reaction in patients with renal impairment. We report a case of acetazolamide-induced Gerstmann syndrome in a patient with normal renal function, to highlight predisposing factors that are frequently overlooked.

Survival of glaucoma patients

PURPOSE

To investigate the survival of patients with capsular or simple glaucoma compared with that of the common population, with particular attention to the impact of sex and use of acetazolamide (Diamox).

METHODS

The 30 year survival of 1147 patients with capsular or simple glaucoma who were finally hospitalized at the Eye Department, Rikshospitalet, Oslo, from 1961 to 1970, are analysed, using log rank tests. The time varying impacts of sex and acetazolamide on survival are also studied using a regression model.

RESULTS

There was a significant increased mortality for patients with acetazolamide, and for men also those not using it. The observed mortality for men was initially lower than the average Norwegian population, but later the mortality increased more rapidly in the glaucoma group. This may be explained by a selection of the healthiest patients to Rikshospitalet, and actually indicates that the excess mortality is even higher than calculated here.

CONCLUSION

The analysis of data indicated increased mortality for glaucoma patients when the disease had lasted for some time. This was especially pronounced for men using acetazolamide. A similar study from a period when acetazolamide was not in common use and an analysis of causes of death is also asked for.

Calcium phosphate stones during long-term acetazolamide treatment for epilepsy

We report a case of recurrent renal calculi containing calcium phosphate associated with long-term acetazolamide treatment for epilepsy. Unfortunately, the cause of stone formation was not recognised for many years, by which time irreversible renal damage had occurred.

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 and furosemide for posthemorrhagic hydrocephalus of the newborn

The authors evaluated the efficacy of acetazolamide (ACZ) and furosemide (FUR) in avoiding ventricular shunting procedures in preterm infants with posthemorrhagic hydrocephalus (PHH) and increased intracranial pressure (ICP). Preterm infants were screened for PHH (defined as ventriculomegaly [VM] and increased ICP measured with the Ladd fiberoptic monitor). PHH infants were randomized to ACZ and FUR treatment or serial lumbar puncture (LP) and monitored until not receiving medications or having undergone shunting. Of 69 infants with IVH screened for the study, 39 never developed VM, 14 developed VM, without increased ICP, and 16 developed PHH. Ten PHH infants were randomized to ACZ and FUR treatment and six to serial LP. Nine (90%) of the 10 infants assigned to the ACZ and FUR group avoided shunting. Nephrocalcinosis developed in a significant proportion of treated infants. Three (50%) of the six LP group infants did not require shunting procedures (P = 0.118). The authors conclude that ACZ and FUR therapy is useful in the treatment of preterm infants with PHH. Because a significant number of infants treated with both ACZ and FUR developed nephrocalcinosis, close monitoring for increased calcium excretion in the urine, or use of ACZ without FUR, is advised.

[Salicylism and glaucoma: reciprocal augmentation of the toxicity of acetazolamide and acetylsalicylic acid]

We report a case of salicylism caused by association of acetylsalicylic acid (ASA) and acetazolamide. A 50-year-old woman without chronic renal insufficiency, was admitted for confusion, cerebellar ataxia associated with hyperchloremic acidosis. She was treated with acetazolamide for simple glaucoma and since 14 days with ASA for acute pericarditis. Clinical features evoked salicylism despite low serum salicylate level: 178 mg/l. The carbonic anhydrase inhibitor explained the biochemical pattern. Acetazolamide-induced acidosis enhances the non ionized form of salicylate which crosses the biological membrane more rapidly and better than the ionized form. The tissular tropism of non ionized salicylate increases and cerebral toxicity may occur with low serum level of ASA. ASA also enhances the free form of acetazolamide.

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.