Levothyroxine 100micrograms Tablets (Thyroxine 100 micrograms Tablets).

Each tablet contains 100 micrograms Levothyroxine Sodium anhydrous also known as thyroxine sodium tablets.

Tablet.

White uncoated biconvex tablets engraved on one face FW31 and with a breakline on the other.

Recommended clinical indications: Control of hypothyroidism, congenital hypothyroidism and juvenile myxoedema.

Adults:

Initially 50 to 100 micrograms daily, preferably taken before breakfast. Adjust at three to four week intervals by 50 micrograms until normal metabolism is steadily maintained: this may require doses of 100 to 200 micrograms daily.

For patients over 50 years, it is not advisable to exceed 50 micrograms daily initially and where there is cardiac disease, 25 micrograms daily or 50 micrograms on alternate days is more suitable initially. In this condition the daily dose may be increased by 25 micrograms at intervals of perhaps 4 weeks.

For patients younger than 50 years, and in the absence of heart disease, a serum Levothyroxine (T4) level of 70 to 160 nanomoles per litre, or a serum thyrotrophin level of less than 5 milli-units per litre should be targeted. For patients aged over 50 years, with or without cardiac disease, clinical response is probably a more acceptable criteria of dosage rather than serum levels.

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 re-started at a lower dose level.

Elderly: As for patients aged over 50 years.

Paediatric patients:

The maintenance dose is generally 100 to 150 micrograms per m² body surface area.

For neonates and infants with congenital hypothyroidism, where rapid replacement is important the initial recommended dosage is 10 to 15 micrograms per kg BW per day for the first 3 months. Thereafter, the dose should be adjusted individually according to the clinical findings and thyroid hormone and TSH values.

For children with acquired hypothyroidism, the initial recommended dosage is 12.5-50 micrograms per day. The dose should be increased gradually every 2-4 weeks according to the clinical findings and thyroid hormone and TSH values until the full replacement dose is reached. Infants should be given the total daily dose at least half an hour before the first meal of the day.

When applicable:

Tablets are to be disintegrated in some water (10 to 15 mL) and the resultant suspension, which must be prepared freshly as required, is to be administered with some more liquid (5-10 mL).

Thyrotoxicosis. Hypersensitivity to any components of Levothyroxine tablets.

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.

An ECG before starting treatment with levothyroxine is advised, as changes induced by hypothyroidism may be confused with evidence of ischaemia.

Special care is needed for the elderly and for patients with symptoms of myocardial insufficiency, or ECG evidence of myocardial infarction.

Levothyroxine sodium should be used with caution in patients with cardiovascular disorders, including angina, coronary artery disease and hypertension.

Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.

Levothyroxine should be introduced very gradually in elderly patients and those with long standing hypothyroidism to avoid any sudden increase in metabolic demands.

Thyroid replacement therapy may cause an increase in dosage requirements of insulin or other anti-diabetic therapy. Care is needed for patients with diabetes mellitus and diabetes insipidus.

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. Seizures have been reported rarely in association with the initiation of levothyroxine sodium therapy, and may be related to the effect of thyroid hormone on seizure threshold.

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.

Anticoagulants: Levothyroxine increases the effect of anticoagulants and it may be necessary to reduce the anticoagulation dosage if excessive, hypoprothrombinaemia and bleeding are to be avoided

Anti-convulsants, such as carbamazepine, primidone and phenytoin, enhance the metabolism of thyroid hormones and increase requirement for thyroid hormones in hypothyroidism.

Anti arrhytmics: Amiodarone may inhibit the de iodination of thyroxine to tri iodothyronine resulting in a decreased concentration of tri iodothyronine, thereby reducing the effects of throid hormones.

Antidiabetics: Blood sugar levels are raised and dosage of anti-diabetic agents may require adjustment.

Beta Blockers: levothyroxine (thyroxine) accelerates metabolism of propranolol.

Antidepressant: Levothyroxine increases receptor sensitivity to catecholamines thus accelerating the response to tricyclic antidepressants (e.g. amitriptyline, imipramine).

Effects of Levothyroxine may be decreased by concomitant sertraline.

Sympathomimetics: The effects of sympathomimetic agents (e.g. adrenaline) are also enhanced.

Cardiac glycosides: If levothyroxine therapy is initiated in digitalised patients, the dose of digitalis may require adjustment. Hyperthyroid patients may need their digoxin dosage gradually increased as treatment proceeds because initially patients are relatively sensitive to digoxin.

Antineoplastics: plasma concentration of levothyroxine (thyroxine) possibly reduced by imatinib.

NSAIDs: False low plasma concentrations have been observed with concurrent anti-inflammatory treatment such as phenylbutazone or acetylsalicylic acid and levothyroxine therapy.

Sex Hormones: Oestrogen, oestrogen containing product (including hormone replacement therapy) and oral contraceptives may increase the requirement of thyroid therapy dosage. Conversely, androgens and corticosteroids may decrease serum concentrations of Levothyroxine-binding globulins.

Lipid regulating drugs: Lovastatin has been reported to cause one case each of hypothyroidism and hyperthyroidism in two patients taking levothyroxine.

General anaesthetics: Isolated reports of marked hypertension and tachycardia have been reported with concurrent ketamine administration.

Metabolism of levothyroxine (thyroxine) accelerated by rifampicin, barbituarates (may increase requirements for levothyroxine (thyroxine) in hypothyroidism)

Absorption of levothyroxine (thyroxine) possibly reduced by antacids, calcium salts, cimetidine, oral iron, sucralfate, colestipol, polystyrene sulphonate resin and cholestyramine (administration should be separated by 4-5 hours).

The safety of levothyroxine treatment during pregnancy is not known, but any possible risk of foetal abnormalities should be weighed against the risk to the foetus of untreated hypothyroidism.

Levothyroxine is excreted in breast milk in low concentrations, and it is contentious whether this can interfere with neonatal screening.

None known.

Side-effects are usually indicative of excessive dosage and usually disappear on reduction of dosage or withdrawal of treatment for a few days. Such effects include:

General: Headache, flushing, fever and sweating

Immune system disorders: hypersensitivity reactions including rash, pruritus and oedema

Metabolic: weight loss

Nervous system: tremor, restlessness, excitability, insomnia. Rarely, benign intracranial hypertension in children.

Rarely, seizures can occur in patients with a known history of epilepsy.

Cardiac: anginal pain, cardiac arrythmias, palpitations, tachycardia

Gastrontestinal: diarrhoea, vomiting

Musculoskeletal and connective tissue: muscle cramps, muscle weakness, craniostenosis in infants and premature closure of epiphysis in children.

Reproductive: menstrual irregularities

Fever, heat intolerance, transient hair loss in children, hypersensitivity reactions including rash, pruritus and oedema also reported.

Symptoms

In most cases there will be no features. Rarely, features of hyperthyroidism may develop 3-6 days after ingestion, with palpitations, tachycardia, tremor, insomnia and hyperpyrexia. Atrial fibrillation may develop. Convulsions occurred in one child. There may be increased toxicity in those with pre-existing heart disease.

Treatment:

Give oral activated charcoal if more than10mg has been ingested by an adult or more than 5mg by a child, within 1 hour. If more than 10mg has been ingested by an adult or more than 5mg by a child, take blood 6-12 hours after ingestion for measurement of the free thyroxine concentration. The analysis does not need to be done urgently but can wait until the first working day after the incident. Patients with normal free thyroxine concentrations do not require follow up. Those with high concentrations should have outpatient review 3-6 days after ingestion to detect delayed onset hyperthyroidism. Features of clinical hyperthyroidism should be controlled with beta-blockers, e.g. propranolol.

Levothyroxine 100 micrograms Tablets are tablets containing Levothyroxine sodium used for the treatment of hypothyroidism. Levothyroxine is deiodinated in peripheral tissues to form triiodothyronine which is thought to be the active tissue form of thyroid hormone. Triiodothyronine has a rapid action but a shorter duration of activity than Levothyroxine.

The chief action of Levothyroxine is to increase the rate of cell metabolism.

Levothyroxine sodium is incompletely and variably absorbed from the gastrointestinal tract. It is almost completely bound to plasma proteins and has a half-life in the circulation of about a week in healthy subjects, but longer in patients with myxoedema.

A large portion of the Levothyroxine leaving the circulation is taken up by the liver.

Part of a dose of Levothyroxine is metabolised to triiodothyronine.

Levothyroxine is excreted in the urine as free drug, deiodinated metabolites and conjugates. Some Levothyroxine is excreted in the faeces. There is limited placental transfer of Levothyroxine.

No further data of relevance

Sodium Citrate

Lactose

Maize starch

Powdered Acacia

Magnesium Stearate

Purified Water

None known.

36 months for polypropylene containers.

24 months for blister packs.

Do not store above 25°C and store in the original container.

Polypropylene container with tamper-evident low density polyethylene lid, containing 28, 56,100, 112 or 1000 Levothyroxine l00microgram tablets.

Blister packaging PVC/PVdC film (heat treated foil/heat seal lacquer) containing 28, 56 and 112 Levothyroxine tablets.

None.

Forley Generics Limited

NLA Tower

12-16 Addiscombe Road

Croydon

CR0 0XT

United Kingdom

PL 16201/0002

Aug 2004

November 2010