Liothyronine sodium tablets are qualitatively similar in biological action to thyroxine but the effect develops in a few hours and lasts for 24 to 48 hours after stopping the treatment.

Used for the treatment of coma of myxedema, the management of severe chronic thyroid deficiency and hypothyroid states occurring in the treatment of thyrotoxicosis.

Liothyronine sodium can be used also in the treatment of thyrotoxicosis as an adjunct to carbimazole to prevent sub-clinical hypothyroidism developing during treatment.

Liothyronine sodium may be preferred for treating severe and acute hypothyroid states because of its rapid and more potent effect, but thyroxine sodium is normally the drug of choice for routine replacement therapy.

Posology

Adults: Starting dose of 10 or 20 micrograms every 8 hours, increasing after one week, if necessary, to the usual recommended daily dose of 60 micrograms in two or three divided doses.

Myxedema Coma: 60 micrograms given by stomach tube, then 20 micrograms every 8 hours. It is more usual to start treatment with intravenous liothyronine.

Adjunct to carbimazole treatment of thyrotoxicosis: 20 micrograms every 8 hours.

Elderly

5 micrograms daily

Paediatric population

5 micrograms daily.

Method of Administration: Oral

• For doses lower than 20 micrograms, the tablet should be allowed to dissolve/disperse in 20 mL of water for 10 minutes, in a small measuring cup.

• The patient should gently swirl the solution occasionally to aid the dissolution/dispersion. The patient should then swirl the solution for a few seconds prior to using a suitable oral syringe to withdraw the amount of liquid corresponding to the dose prescribed (5mL for a 5mcg dose; 10 mL for a 10mcg dose).

• The patient can then squirt the liquid directly into their mouth from the suitable oral syringe by gently pressing the plunger.

Any remaining liquid should be discarded.

Hypersensitivity to the active substance or to any of the excipients listed in section 6.1

Patients with angina of effort or cardiovascular diseases and thyrotoxicosis.

In severe and prolonged hypothyroidism, adrenocortical activity may be decreased. When thyroid replacement therapy is started, metabolism increases more than adrenocortical activity and this can lead to adrenocortical insufficiency requiring supplemental adrenocortical steroids.

Liothyronine sodium treatment may result in an increase in insulin or anti-diabetic drug requirements. Care is required for patients with diabetes mellitus and diabetes insipidus.

Panhypopituitarism or predisposition to adrenal insufficiency (initiate corticosteroid therapy before starting liothyronine), pregnancy, breast-feeding (see section 4.6 Pregnancy and lactation).

In myxoedema, care must be taken to avoid imposing excessive burden on cardiac muscle affected by prolonged severe thyroid depletion. Particular care is needed in the elderly who have a greater risk of occult cardiovascular disease. Baseline ECG is recommended prior to commencement of liothyronine treatment in order to detect changes consistent with ischaemia. Patients should undergo cardiovascular monitoring, including periodic ECGs, during liothyronine treatment. Liothyronine is contraindicated in established myocardial ischaemia (see section 4.3) in which case, levothyroxine, with cautious dose escalation, is recommended instead.

If metabolism increases too rapidly (causing diarrhoea, nervousness, rapid pulse, insomnia, tremors and sometimes anginal pain where there is latent myocardial ischaemia), reduce dose or withhold for 1-2days and start again at a lower dose.

TSH levels should be monitored during treatment to reduce the risk of over- or undertreatment. The risks of over-treatment include atrial fibrillation, osteoporosis and bone fractures.

This medicine contains lactose. Patients with rare hereditary problems of galactose intolerance, total lactase deficiency or glucose-galactose malabsorption should not take this medication.

This medicine contains less than 1 mmol sodium (23 mg) per dose, that is to say essentially 'sodium-free'.

Liothyronine sodium therapy may potentiate the action of anticoagulants. Phenytoin levels may be increased by liothyronine. Anticonvulsants, such as carbamazepine and phenytoin enhance the metabolism of thyroid hormones and may displace thyroid hormones from plasma proteins. Initiation or discontinuation of anticonvulsant therapy may alter liothyronine dose requirements.

If co-administered with cardiac glycosides, adjustment of dosage of cardiac glycoside may be necessary. Colestyramine and colestipol given concurrently reduces gastrointestinal absorption of liothyronine.

Liothyronine raises blood sugar levels and this may upset the stability of patients receiving antidiabetic agents.

Liothyronine increases receptor sensitivity to catecholamines thus accelerating the response to tricyclic antidepressants. A number of drugs may affect thyroid function tests and this should be borne in mind when monitoring patients on liothyronine therapy.

Co-administration of oral contraceptives may result in an increased dosage requirement of liothyronine sodium.

Amiodarone may inhibit the deiodination of thyroxine to triiodothyronine resulting in a decreased concentration of triiodothyronine with a rise in the concentration of inactive reverse triiodothyronine.

As with other thyroid hormones, Liothyronine may enhance effects of amitriptyline and effects of imipramine.

Metabolism of thyroid hormones accelerated by barbiturates and primidone (may increase requirements for thyroid hormones in hypothyroidism).

Requirements for thyroid hormones in hypothyroidism may be increased by oestrogens.

Pregnancy:

Safety during pregnancy is not known. The risk of foetal congenital abnormalities should be weighed against the risk to the foetus of untreated maternal hypothyroidism.

Breast-feeding:

Liothyronine sodium is excreted into breast milk in low concentrations.

This may interfere with neonatal screening programmes.

Fertility:

No data available

None.

The following effects are indicative of excessive dosage and usually disappear on reduction of dosage or withdrawal of treatment for a day or two.

The undesirable effects are listed below by organ class and the following frequency convention:

Not known (cannot be estimated from the available data)

Paediatric population

• Transient hair loss in children (Not Known)

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. Healthcare professionals are asked to report any suspected adverse reactions via Yellow Card Scheme Website: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store

Symptoms:

If patient is seen within a few hours of overdosage: gastric lavage or emesis.

There may be exaggeration of the side effects as well as agitation, confusion, irritability, hyperactivity, headache, sweating, mydriasis, tachycardia, arrhythmias, tachypnoea, pyrexia, increased bowel movements and convulsions.

Management:

Treatment is symptomatic. Tachycardia in adults may be controlled with 40mg propanolol every 6 hours.

Pharmacotherapeutic group: Thyroid hormones, ATC code: H03AA02

Mechanism of action

Liothyronine sodium is a naturally occurring thyroid hormone.

The biological action of Liothyronine sodium is quantitatively similar to that of Levothyroxine sodium, but the effects develop in a few hours and disappear within 24 to 48 hours of stopping treatment.

Absorption

Liothyronine sodium is almost completely absorbed from the gastro-intestinal tract.

Distribution

It is less readily bound to plasma proteins than thyroxine. About 0.5% is in the unbound form.

Elimination

The half-life of liothyronine in euthyroidism is 1 to 2 days. Thyroid hormones do not readily cross the placenta.

Minimal amounts are excreted in breast milk.

No further relevant data.

Lactose BP

Maize starch BP

Acacia powder BP

Sodium chloride BP

Magnesium stearate BP

Industrial methylated spirit BP

Purified water BP

Not applicable

24 months

Do not store above 25˚ C. Store in the original container in order to protect from light.

Tamper-evident polypropylene container with polythene lid, containing 28, 56, 112 and 100 tablets of Liothyronine sodium 20mcg.

Not all pack sizes may be marketed.

None. Any unused medicinal product or waste material should be disposed of in accordance with local requirements.