l-thyroxine sod.: ELTROXIN, ROXIN 100 μg tab. THYRONORM, THYROX 25 μg, 50 μg, 100 μg tabs. Triiodothyronine (Liothyronine) 5, 25 μg tab—25 μg is equivalent to 100 μg of l-thyroxine: not freely available in India. It is occasionally used i.v. along with l-thyroxine in myxoedema coma.
PREPARATIONS
l-thyroxine sod.: ELTROXIN, ROXIN 100 μg tab. THYRONORM, THYROX 25 μg, 50 μg, 100 μg tabs. Triiodothyronine
(Liothyronine) 5, 25 μg tab—25 μg is equivalent to 100
μg of l-thyroxine: not
freely available in India. It is occasionally used i.v. along with l-thyroxine
in myxoedema coma.
Oral bioavailability
of l-thyroxine is ~ 75%, but severe hypothyroidism can reduce oral absorption.
It should be administered in empty stomach to avoid interference by food.
Sucralfate, iron and calcium also reduce l-thyroxine absorption. Enzyme
inducers like rifampin, phenytoin and carbamazepine accelerate metabolism of T4;
dose of l-thyroxine may need enhancement. Clinically, l-thyroxine is preferred
for all indications over liothyronine because of more sustained and uniform
action as well as lower risk of cardiac arrhythmias.
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