LEVOTHYROXINE

Posology In younger patients, and in the absence of heart disease, a serum Levothyroxine (T4) level of 70 to 160 nanomols per litre, or a serum thyrotrophin level of less than 5 milli-units per litre should be targeted. A pre- therapy ECG is valuable because ECG changes due to hypothyroidism may be confused with ECG evidence of cardiac ischaemia.

If too rapid an increase in metabolism is produced (causing diarrhoea, nervousness, rapid pulse, insomnia, tremors, and sometimes anginal pain where there is latent cardiac ischaemia) dosage must be reduced, or withheld, for a day or two, and then restarted at a lower dose level.

Adults Patients under 50 years age:

Initially 100 micrograms daily , preferably taken before breakfast or the first meal of the day. Adjust at three to four week intervals by 50 micrograms until normal metabolism is steadily maintained. The final daily dose may be up to 100 to 200 micrograms.

Patients over 50 years age: a.

Without cardiac disease:

Initially, it is not advisable to exceed 50 micrograms daily. In this condition, the daily dose may be increased by 50 micrograms at intervals of every 3-4 weeks, until stable thyroxine levels are attained. The final daily dose may be up to 50 to 200 micrograms.

b.

With cardiac disease:

Where there is cardiac disease, 25 micrograms daily or 50 micrograms on alternate days is more suitable. In this conditions, the daily dose may be increased by 25 micrograms at intervals of every 4 weeks, until stable thyroxine levels are attained.

The final daily dose may be up to 50 to 200 micrograms. For patients aged over 50 years, with or without cardiac disease, clinical response is probably a more acceptable criteria of dosage rather that serum levels. Elderly Same as that for patients aged over 50 years Paediatric population The maintenance dose is generally 100 to 150 micrograms per m² body surface area.

The dose for children depends on their age, weight and the condition being treated. Regular monitoring using serum TSH levels, as in adults, is required to make sure he/she gets the right dose. Infants should be given the total daily dose at least half an hour before the first meal of the day.

Side-effects are usually indicative of excessive dosage and usually disappear on reduction of dosage or withdrawal of treatment for a few days. Adverse reactions listed below have been observed during clinical studies and/or during marketed use and are based on clinical trial data and classified according to MedDRA System Organ Class.

Frequency categories are defined according to the following convention:

Not known (cannot be estimated from the available data) System organ class Undesirable effects Immune system disorders Hypersensitivity reaction, Endocrine disorders Thyrotoxic crisis1 Psychiatric disorders Restlessness, agitation, insomnia Nervous system disorders Tremor Cardiac disorders Angina pectoris, arrhythmia, palpitations, tachycardia Vascular disorders Flushing Respiratory, thoracic and mediastinal disorders Dyspnoea Gastrointestinal disorders Diarrhoea, vomiting Skin and subcutaneous tissue disorders Hyperhidrosis, alopecia, rash, pruritus Musculoskeletal and connective tissue disorder Arthralgia, muscle spasm, muscular weakness Reproductive system and breast disorders Menstruation irregular General disorders and administration site conditions Headache, pyrexia, malaise, oedema Investigations Weight decreased 1Some patients may experience a severe reaction to high levels of thyroid hormone.

This is called a "thyroid crisis" with any of the following symptoms:

Hyperpyrexia, tachycardia, arrhythmia, hypotension, cardiac failure, jaundice, confusion, seizure and coma Paediatric population Heat intolerance, transient hair loss, benign intracranial hypertension, craniostenosis in infants and premature closure of epiphysis in children.

Reporting of suspected adverse reactions:

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.

2) and those with long standing hypothyroidism to avoid any sudden increase in metabolic demands. Patients with panhypopituitarism or other causes predisposing to adrenal insufficiency may react to levothyroxine treatment, and it is advisable to start corticosteroid therapy before giving levothyroxine to such patients.

Levothyroxine sodium should be used with caution in patients with cardiovascular disorders, including angina, coronary artery disease, hypertension, and in the elderly who have a greater likelihood of occult cardiac disease. To minimise the risk of adverse effects of undetected overtreatment, such as atrial fibrillation and fractures associated with low serum levels of thyroid stimulating hormone (TSH) in older patients, it is important to monitor serum TSH and adjust the dose accordingly during long term use.

In individuals suspected to have cardiovascular disease or to be at high risk, it is important to perform an ECG prior to commencement of levothyroxine treatment in order to detect changes consistent with ischaemia in which case, levothyroxine should be initiated at a low dose, followed by cautious dose escalation to avoid worsening of ischaemia or precipitation of an infarct.

Special care is needed for the elderly and for patients with symptoms of myocardial insufficiency, or ECG evidence of myocardial infarction. Thyroid replacement therapy may cause an increase in dosage requirements of insulin or other anti-diabetic therapy (such as metformin).

Care is needed for patients with diabetes mellitus, and diabetes insipidus. See note above regarding withdrawal of treatment. Subclinical hyperthyroidism may be associated with bone loss. To minimise the risk of osteoporosis, dosage of levothyroxine sodium should be titrated to the lowest possible effective level.

Parents of children receiving thyroid agent should be advised that partial loss of hair may occur during the first few months of therapy, but this effect is usually transient and subsequent regrowth usually occurs. Care is required when levothyroxine is administered to patients with known history of epilepsy.

1. • Thyrotoxicosis • Adrenal gland disorder or adrenal insufficiency • Treatment with Levothyroxine must not be initiated in acute myocardial infarction, acute myocarditis, and acute pancarditis. • Combination therapy of hyperthyroidism with levothyroxine and anti- thyroid agents is not indicated in pregnancy.

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