Overdose : מינון יתר

4.9.     Overdose
This is manifested in adults by thyrotoxicosis. In the event of a thyrotoxic crisis (thyroid storm), substantially reduce the doses or suspend treatment for a few days, then resume it at lower doses, following biological monitoring.
Treatment with levothyroxine solution for injection/infusion must be adjusted (dose reduction or temporary suspension) in the event of severe overdose. In addition, appropriate supportive measures including, in particular, beta-blockers, should be initiated on the basis of the patient’s clinical condition. An elevated T3 level is a reliable indicator of overdosage, more than elevated T4 or fT4 levels.
In overdosage and intoxication, symptoms of moderate to severe increases in metabolism occur (see section 4.8). Depending on the extent of the overdosage it is recommended that treatment is interrupted and that tests are carried out.
In incidents of poisoning in humans, oral doses of 10 mg levothyroxine were tolerated without complications.
Severe complications involving a threat to vital functions (respiration and circulation) are not to be expected, except in coronary heart disease. However, there exist reports on cases of thyrotoxic crisis, cramps, cardiac insufficiency and coma. Isolated cases of sudden cardiac death have been reported in patients with many years of levothyroxine abuse.
In case of acute overdosage, treatment is generally symptomatic and supportive. Beta-blockers may be given if severe beta-sympathomimetic symptoms such as tachycardia, anxiety, agitation and hyperkinesia occur.
Antithyroid drugs are not appropriate, because of prior complete inactivation of the thyroid.
In cases of intoxication with extremely high doses, plasmapheresis may be helpful.
Levothyroxine overdosage requires a prolonged monitoring period. Owing to the gradual transformation of levothyroxine into liothyronine, symptoms may occur with a delay of up to six days.