PRECAUTIONS
General
Weakness, muscle cramps, paresthesias, thirst, anorexia,
and signs of hyponatremia, hypokalemia, and/or hypochloremic alkalosis may
occur following vigorous or excessive diuresis and these may be accentuated by
rigid salt restriction. Rarely, tetany has been reported following vigorous
diuresis. During therapy with ethacrynic acid, liberalization of salt intake
and supplementary potassium chloride are often necessary.
When a metabolic alkalosis may be anticipated, e.g., in
cirrhosis with ascites, the use of potassium chloride or a potassium-sparing
agent before and during therapy with ethacrynic acid may mitigate or prevent
the hypokalemia.
Loop diuretics have been shown to increase the urinary
excretion of magnesium; this may result in hypomagnesemia. The safety and
efficacy of ethacrynic acid in hypertension have not been established. However,
the dosage of coadministered antihypertensive agents may require adjustment.
Orthostatic hypotension may occur in patients receiving
other antihypertensive agents when given ethacrynic acid.
Ethacrynic acid has little or no effect on glomerular
filtration or on renal blood flow, except following pronounced reductions in
plasma volume when associated with rapid diuresis. A transient increase in serum
urea nitrogen may occur. Usually, this is readily reversible when the drug is
discontinued.
As with other diuretics used in the treatment of renal
edema, hypoproteinemia may reduce responsiveness to ethacrynic acid and the use
of salt-poor albumin should be considered.
A number of drugs, including ethacrynic acid, have been
shown to displace warfarin from plasma protein; a reduction in the usual
anticoagulant dosage may be required in patients receiving both drugs.
Ethacrynic acid may increase the risk of gastric
hemorrhage associated with corticosteroid treatment.
Laboratory Tests
Frequent serum electrolyte, CO2 and BUN determinations
should be performed early in therapy and periodically thereafter during active
diuresis. Any electrolyte abnormalities should be corrected or the drug
temporarily withdrawn.
Increases in blood glucose and alterations in glucose
tolerance tests have been observed in patients receiving ethacrynic acid.
Carcinogenesis, Mutagenesis, Impairment Of Fertility
There was no evidence of a tumorigenic effect in a
79-week oral chronic toxicity study in rats at doses up to 45 times the human
dose. Ethacrynic acid had no effect on fertility in a two-litter study in rats
or a two-generation study in mice at 10 times the human dose.
Pregnancy
Pregnancy Category B
Reproduction studies in the mouse and rabbit at doses up
to 50 times the human dose showed no evidence of external abnormalities of the
fetus due to ethacrynic acid.
In a two-litter study in the dog and rat, oral doses of 5
or 20 mg/kg/day (2½ or 10 times the human dose), respectively, did not
interfere with pregnancy or with growth and development of the pups. Although there
was reduction in the mean body weights of the fetuses in a teratogenic study in
the rat at a dose level of 100 mg/kg (50 times the human dose), there was no
effect on mortality or postnatal development. Functional and morphologic
abnormalities were not observed.
There are, however, no adequate and well-controlled
studies in pregnant women. Since animal reproduction studies are not always
predictive of human response, ethacrynic acid should be used during pregnancy
only if clearly needed.
Nursing Mothers
It is not known whether this drug is excreted in human
milk. Because many drugs are excreted in human milk and because of the
potential for serious adverse reactions in nursing infants from ethacrynic
acid, 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.
Pediatric Use
There are no well-controlled clinical trials in pediatric
patients. The information on oral dosing in pediatric patients, other than
infants, is supported by evidence from empiric use in this age group.
For information on oral use in pediatric patients, other
than infants, see INDICATIONS AND USAGE and DOSAGE AND ADMINISTRATION.
Safety and effectiveness of oral in infants have not been
established (see CONTRAINDICATIONS).
Geriatric Use
Of the total number of subjects in clinical studies of
ethacrynic acid/ethacrynate sodium, approximately 224 patients (21%) were 65 to
74 years of age, while approximately 100 patients (9%) were 75 years of age and
over. No overall differences in safety or effectiveness were observed between
these subjects and younger subjects, and other reported clinical experience has
not identified differences in responses between the elderly and younger
patients, but greater sensitivity of some older individuals cannot be ruled
out. (See WARNINGS.)
This drug is known to be substantially excreted by the
kidney, and the risk of toxic reactions to this drug may be greater in patients
with impaired renal function. Because elderly patients are more likely to have decreased
renal function, care should be taken in dose selection, and it may be useful to
monitor renal function. (See CONTRAINDICATIONS.)