SIDE EFFECTS
Adverse reactions, occurring most often early in therapy,
include paresthesias, particularly a “tingling”
feeling in the extremities, hearing dysfunction or tinnitus,
loss of appetite, taste alteration and gastrointestinal
disturbances such as nausea, vomiting and diarrhea; polyuria,
and occasional instances of drowsiness and confusion.
Metabolic acidosis and electrolyte imbalance may occur.
Transient myopia has been reported. This condition invariably
subsides upon diminution or discontinuance of the medication.
Other occasional adverse reactions include urticaria,
melena, hematuria, glycosuria, hepatic insufficiency,
flaccid paralysis, photosensitivity and convulsions. Also
see PRECAUTIONS:
Information for Patients
for possible reactions common to sulfonamide derivatives.
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
(see WARNINGS).
No data are available regarding acetazolamide overdosage
in humans as no cases of acute poisoning with this drug
have been reported. Animal data suggest that acetazolamide
is remarkably nontoxic. No specific antidote is known.
Treatment should be symptomatic and supportive.
Electrolyte imbalance, development of an acidotic state,
and central nervous effects might be expected to occur.
Serum electrolyte levels (particularly potassium) and
blood pH levels should be monitored.
Supportive measures are required to restore electrolyte
and pH balance. The acidotic state can usually be corrected
by the administration of bicarbonate.
Despite its high intraerythrocytic distribution and plasma
protein binding properties, acetazolamide may be dialyzable.
This may be particularly important in the management of
acetazolamide overdosage when complicated by the presence
of renal failure.
Glaucoma
Acetazolamide should be used as an adjunct to the usual
therapy. The dosage employed in the treatment of chronic
simple (open- angle) glaucoma ranges from 250 mg to 1
g of acetazolamide per 24 hours, usually in divided doses
for amounts over 250 mg. It has usually been found that
a dosage in excess of 1 g per 24 hours does not produce
an increased effect. In all cases, the dosage should be
adjusted with careful individual attention both to symptomatology
and ocular tension. Continuous supervision by a physician
is advisable.
In treatment of secondary glaucoma and in the preoperative
treatment of some cases of acute congestive (closed- angle)
glaucoma, the preferred dosage is 250 mg every four hours,
although some cases have responded to 250 mg twice daily
on short- term therapy. In some acute cases, it may be
more satisfactory to administer an initial dose of 500
mg followed by 125 or 250 mg every four hours depending
on the individual case. Intravenous therapy may be used
for rapid relief of ocular tension in acute cases. A complementary
effect has been noted when acetazolamide has been used
in conjunction with miotics or mydriatics as the case
demanded.
Epilepsy
It is not clearly known whether the beneficial effects
observed in epilepsy are due to direct inhibition of carbonic
anhydrase in the central nervous system or whether they
are due to the slight degree of acidosis produced by the
divided dosage. The best results to date have been seen
in petit mal in children. Good results, however, have
been seen in patients, both children and adult, in other
types of seizures such as grand mal, mixed seizure patterns,
myoclonic jerk patterns, etc. The suggested total daily
dose is 8 to 30 mg per kg in divided doses. Although some
patients respond to a low dose, the optimum range appears
to be from 375 to 1000 mg daily. However, some investigators
feel that daily doses in excess of 1 g do not produce
any better results than a 1 g dose. When acetazolamide
is given in combination with other anticonvulsants, it
is suggested that the starting dose should be 250 mg once
daily in addition to the existing medications. This can
be increased to levels as indicated above.
The change from other medications to acetazolamide should
be gradual and in accordance with usual practice in epilepsy
therapy.
Congestive Heart Failure
For diuresis in congestive heart failure, the starting
dose is usually 250 to 375 mg once daily in the morning
(5 mg/ kg). If, after an initial response, the patient
fails to continue to lose edema fluid, do not increase
the dose but allow for kidney recovery by skipping medication
for a day. Acetazolamide yields best diuretic results
when given on alternate days, or for two days alternating
with a day of rest.
Failures in therapy may be due to overdosage or too frequent
dosage. The use of acetazolamide does not eliminate the
need for other therapy such as digitalis, bed rest, and
salt restriction.
Drug- lnduced Edema
Recommended dosage is 250 to 375 mg of acetazolamide
once a day for one or two days, alternating with a day
of rest.
Acute Mountain Sickness
Dosage is 500 mg to 1000 mg daily, in divided doses using
tablets or sustainedrelease capsules as appropriate. In
circumstances of rapid ascent, such as in rescue or military
operations, the higher dose level of 1000 mg 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.
The dosage recommendations for glaucoma and epilepsy
differ considerably from those for congestive heart failure,
since the first two conditions are not dependent upon
carbonic anhydrase inhibition in the kidney which requires
intermittent dosage if it is to recover from the inhibitory
effect of the therapeutic agent.
DRUG INTERACTIONS
No information provided.
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