Levothyroxine: Price, Dosage & Where to Buy

Levothyroxine is a synthetic thyroid hormone (T4 replacement) prescribed for the treatment of hypothyroidism, a condition in which the thyroid gland does not produce sufficient thyroid hormone. It is also used as adjunctive therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer following surgery and radioiodine treatment. This medicine requires a prescription in the United Kingdom and has been available as a generic since 2002.

Levothyroxine is prescribed as replacement therapy in primary, secondary, and tertiary hypothyroidism, whether congenital or acquired, in adults and children including neonates. Primary hypothyroidism arises from the thyroid gland itself, secondary from the pituitary gland, and tertiary from the hypothalamus. It is also indicated as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer in both adult and paediatric populations.

Levothyroxine is not indicated for suppression of benign thyroid nodules and nontoxic diffuse goitre in iodine-sufficient patients, as there are no clinical benefits and overtreatment may induce hyperthyroidism. It is also not indicated for treatment of hypothyroidism during the recovery phase of subacute thyroiditis.

The label lists oral tablets in strengths of 25 ug, 50 ug, 75 ug, 88 ug, 100 ug, 112 ug, 125 ug, 137 ug, 150 ug, 175 ug, 200 ug, and 300 ug. Oral capsules are available in 13 ug, 25 ug, 37.5 ug, 44 ug, 50 ug, 62.5 ug, 75 ug, 88 ug, 100 ug, 112 ug, 125 ug, 137 ug, 150 ug, 175 ug, and 200 ug strengths. Oral solutions and intravenous injections are also available.

The label lists once-daily administration, preferably on an empty stomach, one-half to one hour before breakfast. For adults with hypothyroidism, the full replacement dose is 1.6 mcg per kilogramme per day, though some patients require a lower starting dose. Dosage titration is by 12.5 to 25 mcg increments every four to six weeks as needed until the patient is euthyroid.

Adults at risk for atrial fibrillation or with underlying cardiac disease are started on a lower dose and titrated every six to eight weeks. Geriatric patients also receive a lower starting dose.

Levothyroxine is a synthetic form of thyroxine (T4), one of the two main hormones produced by the thyroid gland. In the body, T4 is converted to triiodothyronine (T3), the more active form of thyroid hormone. Thyroid hormones regulate the body's metabolism, influencing energy production, protein synthesis, and the function of nearly every organ system.

In hypothyroidism, the thyroid produces insufficient hormone, leading to a slowed metabolic rate. Levothyroxine replaces the missing hormone, restoring normal metabolic activity.

The medication works by binding to thyroid hormone receptors in cells throughout the body, thereby normalising the metabolic processes that are impaired in hypothyroidism. The full therapeutic effect may take four to six weeks to develop.

Clinical experience, including data from postmarketing studies, in pregnant women treated with oral levothyroxine to maintain euthyroid state have not reported increased rates of major birth defects, miscarriages, or other adverse maternal or foetal outcomes. Untreated hypothyroidism in pregnancy is associated with a higher rate of complications, including spontaneous abortion, gestational hypertension, pre-eclampsia, stillbirth, and premature delivery, and may have an adverse effect on foetal neurocognitive development. Levothyroxine should not be discontinued during pregnancy, and hypothyroidism diagnosed during pregnancy should be promptly treated.

Pregnancy may increase dose requirements; thyroid-stimulating hormone levels should be monitored and the dose adjusted during pregnancy. After delivery, the dose should return to the pre-pregnancy level immediately. Published studies report that levothyroxine is present in human milk, but no adverse effects on the breastfed infant have been reported.

The label does not provide specific instructions regarding missed doses. Levothyroxine has a long half-life, meaning that hormone levels in the body do not drop rapidly after a single missed dose.

If a dose is missed, it is generally advisable to resume the regular dosing schedule the following day rather than doubling the next dose. Patients who miss multiple doses or are uncertain about what to do should contact their doctor or pharmacist for guidance, as consistent daily dosing is important for maintaining stable thyroid hormone levels.

The label lists storage at 25 degrees Celsius, with excursions permitted to 15 to 30 degrees Celsius. Levothyroxine tablets should be protected from light and moisture to maintain quality.

Store the medicine in its original container with the lid tightly closed, and keep it out of reach of children. Do not store tablets in bathrooms or other areas where they may be exposed to humidity or temperature fluctuations.