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Diamox is a potent carbonic anhydrase inhibitor, effective in the control of fluid secretion (e.g. some types of glaucoma), in the treatment of certain convulsive disorders (e.g. epilepsy), and in the promotion of diuresis in instances of abnormal fluid retention (e.g. cardiac edema).
Diamox is an enzyme inhibitor that acts specifically on ... the hydration of carbon dioxide and the dehydration of carbonic acid. In the eye, this inhibitory action decreases the secretion of aqueous humor and results in a drop in intraocular pressure, a reaction considered desirable in cases of glaucoma. ... The diuretic effect of Diamox is due to its action in the kidney on the reversible reaction involving hydration of carbon dioxide and dehydration of carbonic acid. The result is renal loss of HCO3 ion, which carries out sodium, water, and potassium.
Diamox Sequels sustained-release capsules provide prolonged action to inhibit aqueous humor secretion for 18 to 24 hours after each dose, whereas tablets act for only 8 to 12 hours. ... Blood concentrations of Diamox peak between 3 to 6 hours after administration of Sequels, compared to 1 to 4 hours with tablets.
Placebo-controlled clinical trials have shown that prophylactic administration of Diamox at a dose of 250mg every 8 to 12 hours (or 500mg Sequels once daily) before and during rapid ascent to altitude results in fewer and/or less severe symptoms (such as headache, nausea, shortness of breath, dizziness, drowsiness, and fatigue) of acute mountain sickness (AMS). Pulmonary function is greater in the Diamox treated group, both in subjects with AMS and asymptomatic subjects. The Diamox treated climbers also had less difficulty in sleeping.
Diamox therapy is contraindicated in situations in which sodium and/or potassium blod serum levels are depressed, in cases of marked kidney and liver disease, in suprarenal gland failure, and in hyperchloremic acidosis. It is contraindicated in patients with cirrhosis because of the risk of development of hepatic encephalopathy.
Fatalities have occurred, although rarely, due to severe reactions to sulfonamides including Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia, and other blood dyscrasias.
Caution is advised for patients receiving concomitant high-dose aspirin and Diamox, as anorexia, tachypnea, lethargy, coma, and death have been reported.
Increasing the dose does not increase the diuresis, and may increase the incidence of drowsiness and/or paresthesia. Increasing the dose often results in a decrease in diuresis.
Gradual ascent is desirable to try to avoid acute mountain sickness. If rapid ascent is undertaken and Diamox is used, it should be noted that such use does not obviate the need for prompt descent if severe forms of high altitude sickness occur, i.e. pulmonary edema or cerebral edema.
Long term studies in animals to evaluate the carcinogenic potential of Diamox have not been conducted. In a bacterial mutagenicity assay, Diamox was not mutagenic when evaluated with and without metabolic activation.
The drug had no effect on fertility when administered in the diet to male and female rats at a daily intake of up to four times the maximum recommended human dose. Diamox has been shown to produce birth defects of the limbs in mice, rats, hamsters, and rabbits. There are no adequate and well-controlled studies in pregnant women. Diamox should be used in pregnancy only if the potential benefit justifies the potential risk to the fetus. Because of the potential for serious adverse reactions in nursing infants from Diamox, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.
The safety and effectiveness of Diamox in children have not been established.
Adverse reactions, occurring most often early in therapy, include a "tingling" feeling in the extremities, hearing dysfunction or tinnitus, loss of appetite, taste alteration and gastrointestinal disturbances such as nausea, vomiting, diarrhea, and occasional instances of drowsiness and confusion.
No data are available regarding Diamox overdosage in humans as no cases of acute poisoning with this drug have been reported. Animal data suggest that Diamox is remarkably non-toxic. No specific antidote is known. Treatment should be symptomatic and supportive. Electrolyte imbalance, development of an acidotic state, and central nervous system effects might be expected to occur.
Dosage is 500mg to 1000mg daily, in divided doses using tablets or Sequels as appropriate. In circumstances of rapid ascent, such as in rescue or military operations, the higher dose level of 1000mg is recommended. It is preferable to initiate dosing 24 to 48 hours before ascent and to continue for 48 hours while at high altitude, or longer as necessary to control symptoms.
Store at controlled room temperature (59 to 86 deg F).