LEVOTHYROXINE

What it is

Levothyroxine Lup is available in seven strengths containing levothyroxine sodium 25 micrograms, 50 micrograms, 75 micrograms, 100 micrograms, 125 micrograms, 150 micrograms or 200 micrograms as the active ingredient. The tablets are round, white tablets debossed with the strength on one side and scored in the shape of a plus sign on the other side.

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 Lup is best taken as a single daily dose first thing in the morning with water and on an empty stomach, 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, with regular monitoring of TSH and thyroxine recommended when starting therapy or changing the dose. In adults, therapy should commence with levothyroxine sodium 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 sodium therapy should normally be initiated with low doses (25 or 50 micrograms per day). Maintenance dose in adults is 100 to 200 micrograms per day.

Key safety warnings

Levothyroxine Lup is not bioequivalent on a same-dose basis with Eltroxin. If a decision is made to switch a patient from Eltroxin to Levothyroxine Lup, then prescribers should have a plan for monitoring TSH and should be aware that dose adjustment may be required. Extreme caution is required in patients with a cardiovascular disorder. In the event of cardiovascular effects, the dosage of levothyroxine sodium should be lowered. Even smaller initial dosage (such as 12.5 to 25 micrograms per day) should be used with increments of not more than 25 micrograms per day at not less than two week intervals. Corticosteroid replacement therapy must precede initiation of levothyroxine sodium 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 and decreased bone mineral density, especially in post-menopausal women on greater than replacement doses or receiving suppressive doses. Therefore, it is recommended that patients receiving levothyroxine sodium be given the minimum dose necessary to achieve the desired clinical and biochemical response. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for anorectic effects.

Contraindications

Known hypersensitivity to levothyroxine sodium. Untreated hyperthyroidism. Uncorrected primary or secondary adrenal insufficiency. Thyrotoxicosis. Acute myocardial infarction uncomplicated by hypothyroidism. Acute myocarditis. Acute pancarditis. During pregnancy, combination of levothyroxine and antithyroid agents for the treatment of hyperthyroidism is contraindicated.

Regulatory history

Levothyroxine Lup was first registered on the Australian Register of Therapeutic Goods on 23 December 2022, with registrations for seven strengths (25, 50, 75, 100, 125, 150 and 200 micrograms).