In this episode, I’ll discuss the dose of IV levothyroxine used for myxedema coma.
Myxedema coma is a rare medical emergency with in-hospital mortality of ~30%
When it occurs, myxedema coma is often a result of either:
1. Withdrawal of thyroid therapy or
2. The first sign of thyroid disease
The word ‘coma’ in myxedema coma is somewhat of a misnomer. Most patients do not present with coma but rather severe hypothyroidism with altered consciousness, confusion, or lethargy. Rarely a patient may be extremely agitated/psychotic (referred to as myxedema madness). Left untreated, patients will progress to coma and death.
Because the condition is so rare, the ideal dose of levothyroxine is not known.
Many clinicians also prefer to give liothyronine (T3) along with levothyroxine.
The American Thyroid Association guidelines recommend glucocorticoids first and then state that:
…these patients should be given a loading intravenous dose of 200 to 400 mcg of levothyroxine, with lower doses given for patients who are of smaller stature, older, or who have a history of coronary disease or arrhythmia.
If T3 is also given, the ATA recommends:
An initial liothyronine dose of 5 to 20 mcg may be given, followed by a maintenance dose of 2.5 to 10 mcg every 8 hours, in addition to levothyroxine therapy. As with levothyroxine administration, lower doses of liothyronine should be given to patients who are of smaller stature, older, or who have a history of coronary disease or arrhythmia.
If monotherapy with levothyroxine is chosen and found to be ineffective within 24 hours, T3 should be added to the treatment plan.
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