Diamox (Acetazolamide)

Acetazolamide is available as a 250mg tablet from the generic manufacturer Apotex. DIAMOX tablets contain 250mg acetazolamide in each tablet. DIAMOX belongs to a group of drugs called carbonic anhydrase inhibitors. DIAMOX is an enzyme inhibitor which acts specifically on carbonic anhydrase. It is indicated in the treatment of: i) Glaucoma: DIAMOX is useful in glaucoma (chronic simple (open angle) glaucoma, secondary glaucoma, and perioperatively in acute angle closure glaucoma where delay of surgery is desired in order to lower intraocular pressure) because it acts on inflow, decreasing the amount of aqueous secretion. ii) Abnormal retention of fluids: DIAMOX is a diuretic whose effect is due to the effect on the reversible hydration of carbon dioxide and dehydration of carbonic acid reaction in the kidney. The result is renal loss of HCO3- ion which carries out sodium, water and potassium. DIAMOX can be used in conjunction with other diuretics when effects on several segments of the nephron are desirable in the treatment of fluid retaining states. iii) Epilepsy: In conjunction with other anticonvulsants best results with DIAMOX have been seen in petit mal in children. Good results, however, have been seen in patients, both children and adults, with other types of seizures such as grand mal, mixed seizure patterns, myoclonic jerk patterns etc. ) Glaucoma (simple acute congestive and secondary): Adults: 250 - 1,000mg (1-4 tablets) per 24 hours, usually in divided doses for amounts over 250mg daily. ii) Abnormal retention of fluid: Congestive heart failure, drug-induced oedema. Adults: For diuresis, the starting dose is usually 250 - 375mg (1-11/2 tablets) once daily in the morning. If, after an initial response, the patient fails to continue to lose oedema fluid, do not increase the dose but allow for kidney recovery by omitting a day. Best results are often obtained on a regime of 250 - 375mg (1-11/2 tablets) daily for two days, rest a day, and repeat, or merely giving the DIAMOX every other day. The use of DIAMOX does not eliminate the need for other therapy, eg. digitalis, bed rest and salt restriction in congestive heart failure and proper supplementation with elements such as potassium in drug-induced oedema. For cases of fluid retention associated with pre-menstrual tension, a daily dose (single) of 125-375mg is suggested. iii) Epilepsy: Adults: 250 - 1,000mg daily in divided doses. Children: 8-30mg/kg in daily divided doses and not to exceed 750mg/day. The change from other medication to DIAMOX should be gradual. Elderly: DIAMOX should only be used with particular caution in elderly patients or those with potential obstruction in the urinary tract or with disorders rendering their electrolyte balance precarious or with liver dysfunction.

Adverse reactions during short-term therapy are usually non-serious. Those effects which have been noted include: paraesthesia, particularly a "tingling" feeling in the extremities; some loss of appetite; taste disturbance, polyuria, flushing, thirst, headache, dizziness, fatigue, irritability, depression, reduced libido and occasional instances of drowsiness and confusion. Rarely, photosensitivity has been reported. During long-term therapy, metabolic acidosis and electrolyte imbalance may occasionally occur. This can usually be corrected by the administration of bicarbonate. Transient myopia has been reported. This condition invariably subsides upon diminution or withdrawal of the medication. Gastro-intestinal disturbances such as nausea, vomiting and diarrhoea. DIAMOX is a sulphonamide derivative and therefore some side-effects similar to those caused by sulphonamides have occasionally been reported. These include fever, agranulocytosis, thrombocytopenia, thrombocytic purpura, leukopenia, and aplastic anaemia, bone marrow depression, pancytopenia, rash (including erythema multiforme, Stevens-Johnson Syndrome, toxic epidermal necrolysis), anaphylaxis, crystalluria, calculus formation, renal and ureteral colic, and renal lesions. Rarely, fulminant hepatic necrosis has been reported. Other occasional adverse reactions include: urticaria, melaena, haematuria, glycosuria, impaired hearing and tinnitus, abnormal liver function, renal failure and rarely, hepatitis or cholestatic jaundice, flaccid paralysis, and convulsions.

Acetazolamide is contra-indicated in situations in which sodium and/or potassium blood levels are depressed, in cases of marked kidney and liver dysfunction, suprarenal gland failure, and hyper-chloremic acidosis. Diamox should not be used in patients with hepatic cirrhosis as this may increase the risk of hepatic encephalopathy. Long-term administration of DIAMOX is contra-indicated in patients with chronic non-congestive angle-closure glaucoma since it may permit organic closure of the angle to occur while the worsening glaucoma is masked by lowered intraocular pressure. DIAMOX should not be used in patients hypersensitive to sulphonamides. DIAMOX is a sulphonamide derivative. Sulphonamides may potentiate the effects of folic acid antagonists. Possible potentiation of the effects of folic acid antagonists, hypoglycaemics and oral anti-coagulants may occur. Concurrent administration of acetazolamide and aspirin may result in severe acidosis and increase central nervous system toxicity. Adjustment of dose may be required when DIAMOX is given with cardiac glycosides or hypertensive agents. When given concomitantly, acetazolamide modifies the metabolism of phenytoin, leading to increased serum levels of phenytoin. Severe osteomalacia has been noted in a few patients taking acetazolamide in combination with other anticonvulsants. There have been isolated reports of reduced primidone and increased carbamazepine serum levels with concurrent administration of acetazolamide. Concomitant use with other carbonic anhydrase inhibitors is not advisable because of possible additive effects.