Liothyronine dosage

Levothyroxine is used to treat hypothyroidism (an underactive thyroid gland). Thyroid hormone can be made from beef and pork thyroid, but this lacks standardization and it is difficult to control dosage. The synthetic drug is more desirable. Levothyroxine is one of two important thyroid hormones. It is converted into the second important hormone, liothyronine, in the body. The key step in the synthesis of structures such as levothyroxine is the substitution of an iodonium salt by an iodinated phenol. Siql-like reactions on an aromatic ring are not common, but an iodonium salt provides a good leaving group. 

Exchange therapy - Nhen switching a patient to liothyronine from thyroid levothyroxine or thyroglobulin, discontinue the other medication, initiate liothyronine at a low dosage, and increase gradually according to the patient s response. Liothyronine has a rapid onset of action and that residual effects of the other thyroid preparation may persist for the first several weeks of therapy. 

A patient with myxoedema required a gradual reduction in his dosage of phenindione from 200 to 75 mg daily as his thyroid status was corrected by liothyronine. A similar patient required a reduction in acenocoumarol dose from 16 mg daily to 5 mg daily when hypothyroidism was corrected with Uothyronine. ... 

An established interaction (although the documentation is very limited) and of clinical importance. In vitro tests show that liothyronine interacts similarly. The interaction can be minimised by separating the dosages by 4 to 6 hours (but see Mechanism ). Even so, the outcome should he monitored so that any necessary thyroid hormone dosage adjustments can he made. 

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