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|Drug Name and Strength||Thyroxine 400 micrograms|
|Indication||Thyroid hormone replacement therapy in conditions of inadequate thyroid hormone production in dogs and cats.|
|Contraindications||Administration to hyperthyroid animals, cases of acute myocardial infarction or uncorrected hypoadrenocorticism.|
|Actions||Oral thyroxine is up to 80% absorbed after oral administration, mainly from the jejunum and upper ileum. Absorption is reported to increase with age and fasting. Metabolism is the via liver and kidneys, primarily by de-iodination, with about 80% excreted via the kidney.When T4 levels are inadequate, thyroxine supplements both T3 and T4 serum levels, correcting metabolic abnormalities. It increases protein metabolism, use of carbohydrates, energy expenditure, heat production and oxygen consumption, and promotes growth and development.|
|Precautions||Use with caution in patients with heart disease, hypertension, or any entity causing increased metabolic rate. Thyroxine can enhance anticoagulant action. Treat hypoadrenocorticism first. The effects of thyroxine therapy can be slow to manifest.T4 blood levels should be monitored at four weeks. For peak values, test serum thyroxine levels four to eight hours after dosing; levels should be in the high normal or above normal range, but never exceeding 100 nanomol/L. For trough values, test just prior to dosing; levels should be in the normal range.It is recommended that the brand of thyroxine supplement used to treat hypothyroidism is not changed during therapy. Significant variation in the bioavailability of thyroxine is seen between individuals and also between formulations. It is not easy to predict whether a given animal will need a higher, lower or the same dose of a different formulation if a change is made, because of these variations. If a change to a different formulation (brand) is necessary, it is advisable to re-evaluate thyroxine levels after approximately four weeks to ensure the dose is appropriate.Use with caution in pregnant and lactating animals.First Aid If poisoning occurs, get to a doctor or hospital quickly.|
|Dosage and Administration||Dogs. Initially 0.02 mg/kg twice daily. Dosage can then be adjusted by monitoring thyroid hormone blood levels. Once clinical improvement is seen, many dogs require only once daily dosing. Cats. 0.05 to 0.2 mg once daily.|
|Storage||Store below 30°C (room temperature).|
|MSDS (external link)||Thyroxine Tablets 0.4mg MSDS|
|Label (external link)||Thyroxine Tablets 0.4mg Label|
|Manufacturer||Apex Laboratories Pty Ltd|