OVERDOSAGE
Signs and Symptoms
Headache, irritability, nervousness, sweating, arrhythmia
(including tachycardia), increased bowel motility and menstrual irregularities.
Angina pectoris or congestive heart failure may be induced or aggravated. Shock
may also develop. Massive overdosage may result in symptoms resembling thyroid
storm. Chronic excessive dosage will produce the signs and symptoms of
hyperthyroidism.
Treatment Of Overdosage
Dosage should be reduced or therapy temporarily discontinued if
signs and symptoms of overdosage appear. Treatment may be reinstituted at a
lower dosage. In normal individuals, normal hypothalamic-pituitary-thyroidaxis
function is restored in 6 to 8 weeks after thyroid suppression.
Treatment of acute massive thyroid hormone overdosage is aimed at reducing
gastrointestinal absorption of the drugs and counteracting central and
peripheral effects, mainly those of increased sympathetic activity. Vomiting may
be induced initially if further gastrointestinal absorption can reasonably be
prevented and barring contraindications such as coma, convulsions, or loss of
the gagging reflex. Treatment is symptomatic and supportive. Oxygen may be
administered and ventilation maintained. Cardiac glycosides may be indicated if
congestive heart failure develops. Measures to control fever, hypoglycemia, or
fluid loss should be instituted if needed. Antiadrenergic agents, particularly
propranolol, have been used advantageously in the treatment of increased
sympathetic activity. Propranolol may be administered intravenously at a dosage
of 1 to 3 mg over a 10-minute period or orally, 80 to 160 mg/day, especially
when no contraindications exist for its use.
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CONTRAINDICATIONS
Thyroid hormone preparations are generally contraindicated in
patients with diagnosed but as yet uncorrected adrenal cortical insufficiency,
untreated thyrotoxicosis and apparent hypersensitivity to any of their active or
extraneous constituents. There is no well-documented evidence from the
literature, however, of true allergic or idiosyncratic reactions to thyroid
hormone.
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