OVERDOSE
The oral LD50 of spironolactone is greater than 1,000
mg/kg in mice, rats, and rabbits. The oral LD50 of hydrochlorothiazide
is greater than 10 g/kg in both mice and rats.
Acute overdosage of spironolactone may be manifested
by drowsiness, mental confusion, maculopapular or erythematous
rash, nausea, vomiting, dizziness, or diarrhea. Rarely,
instances of hyponatremia, hyperkalemia (less commonly
seen with Aldactazide because the hydrochlorothiazide
component tends to produce hypokalemia), or hepatic coma
may occur in patients with severe liver disease, but these
are unlikely due to acute overdosage.
However, because Aldactazide contains both spironolactone
and hydrochlorothiazide, the toxic effects may be intensified,
and signs of thiazide overdosage may be present. These
include electrolyte imbalance such as hypokalemia and/or
hyponatremia. The potassium-sparing action of spironolactone
may predominate and hyperkalemia may occur, especially
in patients with impaired renal function. BUN determinations
have been reported to rise transiently with hydrochlorothiazide.
There may be CNS depression with lethargy or even coma.
Treatment
Induce vomiting or evacuate the stomach by lavage. There
is no specific antidote. Treatment is supportive to maintain
hydration, electrolyte balance, and vital functions.
Patients who have renal impairment may develop spironolactone-induced
hyperkalemia. In such cases, Aldactazide should be discontinued
immediately. With severe hyperkalemia, the clinical situation
dictates the procedures to be employed. These include
the intravenous administration of calcium chloride solution,
sodium bicarbonate solution and/or the oral or parenteral
administration of glucose with a rapid-acting insulin
preparation. These are temporary measures to be repeated
as required. Cationic exchange resins such as sodium polystyrene
sulfonate may be orally or rectally administered. Persistent
hyperkalemia may require dialysis.
CONTRAINDICATIONS
Aldactazide is contraindicated in patients with anuria,
acute renal insufficiency, significant impairment of renal
excretory function, or hyperkalemia, and in patients who
are allergic to thiazide diuretics or to other sulfonamide-derived
drugs. Aldactazide may also be contraindicated in acute
or severe hepatic failure.
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