Hematologic reactions to carbonic anhydrase inhibitors

The National Registry of Drug-Induced Ocular Side Effects has received 79 case reports of suspected hematopoietic toxicity caused by carbonic anhydrase inhibitors. Twenty-six of these suspected cases (32%) resulted in death secondary to aplastic anemia, thrombocytopenia, or agranulocytosis. In 54 of these 79, adverse reactions (68%) occurred during the first six months of therapy.

Management of hydrocephalus in infancy: use of acetazolamide and furosemide to avoid cerebrospinal fluid shunts

Despite its effectiveness, cerebrospinal shunting for hydrocephalus continues to be accompanied by considerable complications and morbidity. Medical therapy with acetazolamide 100 mg/kg/day and furosemide 1 mg/kg/day can be an effective alternative to shunting by halting progression of hydrocephalus until such time as sutures can become fibrosed and spontaneous arrest can occur. In an appropriately selected population older than 2 weeks with hydrocephalus of varied origin, our success rate in avoiding shunting is greater than 50%. The dramatic difference between the number of hospitalizations of patients with shunts and those treated medically, and the potential to avoid shunt dependence would appear to make an initial trial with medical therapy worthwhile.

Effect of acetazolamide (Diamox) on tear secretion

The side effects of acetazolamide (Diamox) on lacrimation were measured in rats by means of the cotton-thread tear test. After a daily oral 1-mg dose (administered for five days), comparable to the dose used for adult humans on a drug-to-bodyweight basis, tear production remained unaffected but the lacrimal peroxidase secretion decreased by 60% of the baseline level. After withdrawal of acetazolamide the peroxidase secretion returned to the baseline level.

Hypotony and ciliochoroidal detachment following pharmacologic aqueous suppressant therapy in previously filtered patients

This is the first report describing the syndrome of hypotony and ciliochoroidal detachment following pharmacologic aqueous suppressant therapy in previously filtered eyes. Four patients had a history of advanced primary open-angle glaucoma treated with multiple medical therapies, including timolol for 11 to 36 months. They then underwent filtration surgery, which failed in two cases. Timolol and/or acetazolamide therapy was instituted 1 to 18 months following surgery. The patients then developed hypotony and ciliochoroidal detachment, which resolved spontaneously after cessation of the pharmacologic aqueous suppressant therapy. In three of the cases, the episode of hypotony and ciliochoroidal detachment recurred after a second challenge with timolol and/or acetazolamide therapy. Inflammation, tumor, wound leakage, retinal detachment and cyclodialysis cleft were excluded. A mechanism of formation of ciliochoroidal detachment in this syndrome is proposed. Long-term timolol therapy followed by filtration surgery and its attendant postoperative hypotony and ciliochoroidal detachment sensitizes the ciliary epithelium. Subsequent pharmacologic aqueous suppressant therapy results in almost total reduction of aqueous production, causing hypotony and ciliochoroidal detachment.

Adverse drug reactions in the elderly: case studies

ADRs in the elderly may present in an atypical manner. Atypical reactions are uncommon and usually cannot be anticipated from the chemical or pharmacologic properties of the drug. In many cases, you may find a careful and thorough drug history and knowledge of drug-related reactions more helpful than an array of laboratory data.

Oral acetazolamide in Menière's disease

The therapeutic efficacy of oral acetazolamide has been evaluated in a small pilot study of 14 patients with Menière's disease (23 hydropic ears). Symptomatic improvement was found in 4 cases. In 2 of these patients the improvement was not sustained, whilst another had to stop the drug due to the development of bilateral renal calculi. A deterioration in symptoms was seen in 3 cases. Significant adverse side-effects were encountered in 6 of the 13 patients (46.2 per cent) who complied with drug dosage instructions. It is suggested that this high incidence of side-effects may be consistent with a general metabolic difference between Menière's patients and normal subjects. We conclude that oral acetazolamide has no place in the medical treatment of Menière's disease.

Zinc therapy of acetazolamide-induced side-effects

A double-blind cross-over trial extending over 4 weeks with administration of 0.2 g zinc sulphate 3 times daily and a placebo was carried out on 12 patients having grave acetazolamide-induced side-effects manifesting themselves as gustatory disorder, anorexia, and paraesthesia. All the patients had S-zinc levels within the normal range. These rose during zinc therapy periods, to fall again within placebo periods. Recording of the degrees of subjective side-effects based on interviews showed the side-effects to abate towards the conclusion of the trial period, independently of the randomizing programme. In other words, no significant difference was demonstrable between zinc period and placebo period. Taste tests according to Börnstein showed the gustatory disorders to be related exclusively to beverages containing carbon dioxide. However, in no more than 3 out of 10 patients did the gustatory sense return to normal after administration of zinc and one after placebo. Thus, this controlled trial has not served to disclose any statistically significant effect of zinc administration on acetazolamide-induced side-effects.

Acetazolamide teratogenesis: association of maternal respiratory acidosis and ectrodactyly in C57BL/6J mice

Exposure of C57BL/6J mice to CO2 during a critical period of gestation results in predominantly right-sided, postaxial, forelimb ectrodactyly in the offspring. The incidence and severity of CO2-induced limb malformations has been shown to be dependent on the concentration of inspired CO2, the developmental age of the embryo at exposure and the duration of CO2 exposure. Offspring of acetazolamide-treated C57BL/6J mice also display this highly specific form of ectrodactyly (Green et al., '73). Since the drug has been shown to elevate tissue CO2 tension (Mithoefer and Davis, '58), the teratogenic effect of acetazolamide may be related to induction of a hypercapnic embryonic environment.

Acetazolamide teratogenesis: interaction of maternal metabolic and respiratory acidosis in the induction of ectrodactyly in C57BL/6J mice

Exposure of C57BL/6J mice to 20% CO2 for 8 hours on day 10 of gestation has been shown to produce right-sided postaxial forelimb ectrodactyly in 23% of the offspring. Carbon dioxide exposure produces a dramatic increase in maternal plasma CO2 accompanied by an inevitable decrease in plasma pH, both of which appear to be involved in the induction of ectrodactyly. However, the low incidence of ectrodactyly associated with NH4Cl-induced metabolic acidosis suggests that the primary teratogenic factor in respiratory acidosis is elevated CO2 tension. This conclusion is supported by the observation that moderation of maternal plasma pH in the face of sustained elevated PCO2 fails to reduce the incidence of ectrodactyly; moreover, there is a strong correlation between maternal serum CO2 content and the incidence of ectrodactyly.

Metabolic acidosis induced by carbonic anhydrase inhibitors and salicylates in patients with normal renal function

Two young patients with unimpaired renal and hepatic function were found to have developed metabolic acidosis after treatment for glaucoma and joint pain with a combination of salicylates and carbonic anhydrase inhibitors in normal doses. Carbonic anhydrase inhibitors appear to interact with salicylates to produce serious metabolic acidosis in patients without the predisposing factors generally considered to constitute risks. It is recommended that treatment combining salicylates and carbonic anhydrase inhibitors is either kept to a minimum or avoided.

Adverse interaction between acetazolamide and anticholinesterase drugs at the normal and myasthenic neuromuscular junction level

At skeletal neuromuscular junction level in vivo and in vitro experiments have revealed an adverse reversible interaction between acetazolamide and anticholinesterase drugs. Acetazolamide (500 mg, i.v.) prevented the increase in amplitude induced by edrophonium (5 mg, i.v.) on the action potentials derived by surface electrodes from the opponens pollicis muscle of patients affected by myasthenia gravis, when the median nerve was stimulated at the wrist by low frequency repetitive pulses (5/s). Similarly, acetazolamide significantly reduced the contractile force potentiation induced by neostigmine on the rat phrenic-diaphragm preparation, indirectly stimulated by means of low frequency repetitive pulses on the motor nerve. Under such experimental conditions acetazolamide did not show any significant action of its own, but it counteracted the effects of anticholinesterase drugs only when tested before them. It is hypothesized that the effect of acetazolamide on the skeletal neuromuscular junction may occur at presynaptic and/or postsynaptic sites by a mechanism only partly ascribable to the well-known carbonic anhydrase inhibitory activity of this drug.

A retrospective look at twenty-two medicolegal claims. How they might have been avoided

Selected cases from the author's study of 500 medicolegal claims illustrate the need for caution and precaution in several aspects of eye care. Injections with disposable needles, the delegation of responsibility, complications of intraocular surgery, incomplete localization or removal of foreign bodies, complications of photocoagulation, and the prescribing of drugs are discussed. Suggestions are made regarding procedures for diminishing the incidence of certain complications.

Methazolamide and acetazolamide in acute mountain sickness

Methazolamide (150 mg/d) was as effective as acetazolamide (500 mg/d) in preventing the symptoms of acute mountain sickness in 20 subjects ascending to 4985 m. PaO2 and oxygen saturation levels were similar on the two drugs but the fall in PaCO2 was greater on acetazolamide. Paraesthesiae, a side-effect of carbonic anhydrase inhibitors, tended to be less at high altitude on methazolamide and was significantly less when taking 100 mg/d at low altitude. It is likely that paraesthesiae is similar on the two drugs when given in doses that affect blood gases equally.

Benign intracranial hypertension, monoclonal gammopathy, and superior sagittal sinus thrombosis

We report a case of benign intracranial hypertension associated with monoclonal gammopathy. The course was complicated by superior sagittal sinus thrombosis which we believe to be related to acetazolamide therapy. Response to volume expansion with colloid and crystalloid solutions was dramatic.

Cardiovascular performance and oxyhemoglobin dissociation after acetazolamide in metabolic alkalosis

In patients with metabolic alkalosis, compensatory alveolar hypoventilation may induce hypercapnia and hypoxemia. In edematous or normally-hydrated patients without electrolyte deficiencies, acetazolamide--a carbonic anhydrase inhibitor--has been advocated to correct the primary acid-base disturbance, thereby preventing hypoxemia. The hemodynamic consequences and the effect on oxyhemoglobin dissociation of acetazolamide, were studied. Twelve critically ill patients with metabolic alkalosis were given 15 mg/kg body wt. acetazolamide intravenously. Cardiovascular performance was completely unchanged. The P50 was 26.6 mm Hg at the beginning and the end of the study, indicating that hemoglobin-oxygen affinity is unaffected by acetazolamide. In six patients, investigated after open-heart surgery, the arterial oxygen tension increased by 10-45%. This was probably related to the combined effects of slight reductions in total body oxygen consumption or shunting of venous blood through the lungs. Eight of the 12 patients were on controlled ventilation. After acetazolamide there was a mean increase in mixed venous carbon dioxide tension (PvCO2) of 4.5 mm Hg, with no increase in arterial carbon dioxide tension (PaCO2), indicating only a limited interference with carbon dioxide uptake and release of the carbonic anhydrase inhibition. No other adverse reactions were observed.

Hypokalemic periodic paralysis exacerbated by acetazolamide

Although acetazolamide usually prevents paralytic attacks in hypokalemic periodic paralysis, not all patients benefit from this treatment. We studied a father and two sons in whom attack frequency and severity increased on acetazolamide. Administration of triamterene virtually abolished attacks in three separate single-blind trials totaling more than 12 months. Spontaneous and glucose-insulin provoked occurred with only slight hypokalemia. Acetazolamide produced slight hypokalemia and provoked attacks of weakness whereas triamterene increased potassium levels significantly. Certain patients with hypokalemic periodic paralysis are worsened by acetazolamide, perhaps because of its kaliopenic effect. Triamterene may be effective in some of these patients.

Reducing side effects of carbonic anhydrase inhibitors

Carbonic anhydrase inhibitor (CAI) side effects are common, but not well understood. Many ideas have surfaced on how to reduce these side effects, even though there is little scientific evidence to support some of the advice. One recommendation involves switching drugs when patients are intolerant of a particular CAI agent. This study included 44 glaucoma patients who needed a CAI drug. All patients were placed on acetazolamide tablets 250 mg qid. Of those who could not tolerate this drug (26 patients), 22 were switched to methazolamide. Half of these 22 (50%) were considered to have "severe" side effects to methazolamide, while 88% of them had "severe" side effects to acetazolamide. Reduction of intraocular pressure was similar on the two drugs. Other than switching drugs to reduce CAI side effects, one can try reduced dosages, a gradual dosage increase, and patience. Administering sodium bicarbonate or potassium, or taking the CAI drug with meals are unproven remedies.

[Report on the application of chibro-timoptol after one year's use in ophthalmological practice (author's transl)]

A summary is given of the common methods of treating glaucoma medically, beginning with the introduction of pilocarpine over 100 years ago and ending, for the time being, with the application of the beta-blocker Timolol Maleat (Chibro-Timoptol). The authors have been using Chibro-Timoptol for over a year and have treated more than 300 patients by this method so far. Timolol proved to have significant advantages over all other pressure-lowering drugs used in the past. It was just as effective or more effective than the substances used previously. For a newly diagnosed glaucoma, the authors therefore recommend using Timolol in all initial attempts at pressure regulation.

Fetal exposure to anticonvulsant drugs. Detailed pathological study of a case

Autopsy findings are discussed of a 23-month-old child exposed in utero to anticonvulsant therapy. Major abnormalities were confined to the heart and brain. The former consisted of massive biventricular hypertrophy with chamber obliteration. Except for generalized cerebral gliosis, the abnormalities in the brain were confined to the cerebellum, where malformation of the dentate nuclei, neuronal heterotopias, and abnormalities of Purkinje's cell dendrites were found. These findings lend further evidence for anticonvulsant teratogenicity.

Life-threatening hypophosphatemia in a patient with acute myelogenous leukemia

A patient with acute myelogenous leukemia developed severe hypophosphatemia manifesting by extreme weakness, confusion, loss of sphincter control, nuchal rigidity, hyperesthesia, hemolysis, congestive heart failure and liver dysfunction. The possible causes for this condition were starvation, parenteral glucose and saline administration, sepsis, hypokalemia and treatment with acetazolamide. A dramatic improvement was noted following phosphate administration.

[Plasma and intra-erythrocyte variations in acid-base equilibrium in acute acidosis due to acetazolamide loading]

Plasma and red cell acid-base equilibrium was studied in 14 healthy subjects following the induction of acidosis by means of i.v. acetazolamide. It was found that changes in red cell values were significantly less marked than those in plasma.

Severe acidosis from acetazolamide in a diabetic patient

An insulin-dependent diabetic patient with nephropathy developed severe acidosis after treatment with acetazolamide for glaucoma. A renal tubular abnormality may have allowed the usually self-limiting acidosis of acetazolamide to progress. It is suggested that the plasma electrolytes of patients at risk should be monitored.

Gastrointestinal therapeutic system for acetazolamide. Efficacy and side effects

Acetazolamide has been formulated in a new gastrointestinal therapeutic system that delivers the drug at an essentially constant rate of 15 mg/hr (GITS 15/125). We compared the therapeutic effect, magnitude of plasma concentration fluctuations, and incidence of side effects produced by the GITS 15/125 with conventional 250-mg acetazolamide tablets on eight glaucomatous patients randomly assigned to a different regimen each week. One or two GITS 15/125 twice a day (bid) were found as effective in reducing intraocular pressure as one 250-mg acetazolamide tablet. Plasma concentration fluctuations with the GITS 15/125 were decreased, compared with acetazolamide tablets, and, as a result, the incidence of drowsiness, tingling feet, tingling hands, and confusion was substantially reduced.

Carbonic anhydrase inhibition in glaucoma: hazard or benefit for the chronic lunger?

Carbonic anhydrase inhibitors, of proven value in the longterm management of glaucoma, have a number of troublesome side effects, most of which are well-known. However, their potential hazards to patients with chronic obstructive lung disease have received little attention. The author reviews the physiological effects of carbonic anhydrase inhibition on carbon dioxide metabolism and the implications for the chronic lung patient. The untoward pulmonary complications associated with the use of carbonic anhydrase inhibitors are of particular importance to ophthalmologists, since chronic lung disease and glaucoma, both common disorders in the elderly, frequently coexist in the same patient.

Toxicity of combined therapy with carbonic anhydrase inhibitors and aspirin

A 67-year-old woman and a 75-year-old woman taking carbonic anhydrase inhibitors for therapy of glaucoma and high doses of aspirin for therapy of arthritis developed severe acid-base imbalance and salicylate intoxication. Neither patient exhibited ill effects when taking high aspirin doses without carbonic anhydrase inhibitor. Carbonic anhydrose inhibitor-induced acidemia increases the risk of developing salicylate intoxication in patients receiving high aspirin doses.