ELTROXIN

What it is

Eltroxin is levothyroxine sodium presented as a tablet. The tablets are available in eleven strengths: 25 microgram, 50 microgram, 75 microgram, 88 microgram, 100 microgram, 112 microgram, 125 microgram, 137 microgram, 150 microgram, 175 microgram and 200 microgram. Eltroxin is not bioequivalent on a same-dose basis with other levothyroxine containing products.

Approved indications

— Management of demonstrated thyroid hormone deficiency. — Suppression of thyrotropin (TSH) for the management of TSH-responsive tumours of the thyroid.

Dosing overview

Levothyroxine is best taken as a single daily dose first thing in the morning, with water on an empty stomach, and at least 30 minutes and preferably 60 minutes before the intake of any food or other medications. The dose should be individualised on the basis of clinical response and biochemical tests, and regular monitoring of TSH and levothyroxine is recommended when starting therapy or changing the dose. **Adults:** Initial dosing commences with levothyroxine 50 to 100 micrograms daily, with the daily dose increased by 25 to 50 micrograms according to response at not less than 4-weekly intervals, up to 100 to 200 micrograms daily. In patients aged 60 years and over and in those with ischaemic heart disease, levothyroxine therapy should normally be initiated with low doses (25 or 50 μg/day). Maintenance doses for adults are 100 to 200 μg per day. **Children:** Levothyroxine dosing for congenital and acquired hypothyroidism in children is approximately 8 μg per kg per day for ages 0 to 6 months, 6 μg per kg per day for ages 6 to 12 months, 5 μg per kg per day for ages 1 to 5 years, 4 μg per kg per day for ages 6 to 12 years, and 2 μg per kg per day for ages 12 years and over.

Key safety warnings

Eltroxin should not be interchanged with other levothyroxine containing products; if a decision is made to switch from another levothyroxine product to Eltroxin, dose adjustment may be required and TSH should be monitored. In the elderly or patients with ischaemic heart disease, Eltroxin should not be initiated at more than 50 μg/day and should be gradually increased; extreme caution is required in patients with a cardiovascular disorder, and in the event of cardiovascular effects the dosage should be lowered, with even smaller initial dosage (for example 12.5 to 25 μg/day) used with increments of not more than 25 μg/day at not less than two week intervals. Corticosteroid replacement therapy must precede initiation of Eltroxin therapy to avoid Addisonian crisis in such conditions as hypopituitarism and adrenal insufficiency. In women, long-term levothyroxine sodium therapy has been associated with increased bone resorption, thereby decreasing bone mineral density, especially in post-menopausal women on greater than replacement doses or in women receiving suppressive doses; the increased bone resorption may be associated with increased serum levels and urinary excretion of calcium and phosphorus, elevations in bone alkaline phosphate and suppressed serum parathyroid hormone levels, and it is recommended that patients receiving levothyroxine sodium be given the minimum dose necessary to achieve the desired clinical and biochemical response. Caution is required when Eltroxin is given to hypothyroid patients with diabetes mellitus or diabetes insipidus, as it may cause the required dosage of insulin and oral antidiabetic agents to be increased, and careful monitoring of diabetic control is recommended, especially when Eltroxin therapy is initiated, changed or discontinued.

Contraindications

Eltroxin is contraindicated in known hypersensitivity to thyroxine, untreated hyperthyroidism, uncorrected primary or secondary adrenal insufficiency, thyrotoxicosis, acute myocardial infarction uncomplicated by hypothyroidism, acute myocarditis and acute pancarditis. During pregnancy, combination of levothyroxine and antithyroid agents for the treatment of hyperthyroidism is contraindicated.

PBS listing

Eltroxin 125 microgram tablets are listed on the PBS with a restriction status, at an ex-manufacturer price of A$10.68 per unit.

Regulatory history

Eltroxin was first registered on the ARTG on 19 May 2014 across eleven strengths (25, 50, 75, 88, 100, 112, 125, 137, 150, 175 and 200 microgram tablets). In November 2015, the PBAC recommended Eltroxin as a new listing for thyroid hormone deficiency and TSH-responsive tumours of the thyroid with unrestricted benefit listing for five strengths (50, 75, 100, 125 and 200 micrograms), did not recommend the 25 microgram strength, and noted the non-substitutability of brands.