Summary of Product Characteristics (SmPC) - Liothyronine Sodium 5 micrograms tablets
1 NAME OF THE MEDICINAL PRODUCT
Liothyronine Sodium 5 micrograms Tablets
2 QUALITATIVE AND QUANTITATIVE COMPOSITION
Each tablet contains 5 micrograms liothyronine sodium
For the full list of excipients, see section 6.1.
3 PHARMACEUTICAL FORM
Tablets ∑
White to off-white, round tablets, embossed with “76” on one side and “plain” on the other side, and 6.35 mm in diameter.
4 CLINICAL PARTICULARS
4.1 Therapeutic indications
Used for the treatment of coma of myxoedema, 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.
4.2 Posology and method of administration
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.
Myxoedema 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 and Paediatric Population
5 micrograms daily.
Method of administration
For oral use only.
For patients who have difficulty in swallowing a whole tablet, such as the elderly and young children, a whole tablet may be crushed and allowed to dissolve in a minimum of 20 mL of water. The entire volume of liquid should be consumed to ensure ingestion of the full dose.
The solubility of liothyronine in water enables this as a method of administration.
4.3 Contraindications
Hypersensitivity to the active substance(s) or to any of the excipients listed in section
6.1.
Patients with angina of effort or cardiovascular diseases and thyrotoxicosis.
4.4 Special warnings and precautions for use
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 rather than levothyroxine would be the replacement therapy of choice during block and replace treatment of thyrotoxicosis with propylthiouracil (PTU) due to the inhibition by PTU of the peripheral conversion of T4 to T3.
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, insomina, tremors and sometimes anginal pain where there is latent myocardial ischaemia), reduce dose or withhold for 1-2 days 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 overtreatment include atrial fibrillation, osteoporosis and bone fractures.
Interferences with laboratory test:
Biotin may interfere with thyroid immunoassays that are based on a biotin/streptavidin interaction, leading to either falsely decreased or falsely increased test results. The risk of interference increases with higher doses of biotin. When interpreting results of laboratory tests, possible biotin interference has to be taken into consideration, especially if a lack of coherence with the clinical presentation is observed.
For patients taking biotin-containing products, laboratory personnel should be informed when a thyroid function test is requested. Alternative tests not susceptible to biotin interference should be used, if available. (see section 4.5)
4.5 Interaction with other medicinal products and other forms of interaction
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 antidepressents. 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 triidothyronine 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 hyprothyroidism may be increased by oestrogens.
Interferences with laboratory test:
Biotin may interfere with thyroid immunoassays that are based on a biotin/streptavidin interaction, leading to either falsely decreased or falsely increased test results (see section 4.4).
4.6 Fertility, pregnancy and lactation
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 human or animal data on the effect of active substance liothyronine on fertility are available.
4.7 Effects on ability to drive and use machines
Liothyronine Sodium Tablets have no influence on the ability to drive and use machines.
4.8 Undesirable effects
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: very common (≥ 1/10), common (≥ 1/100 to < 1/10), uncommon (≥ 1/1,000 to < 1/100), rare (≥ 1/10,000 to < 1/1,000), not known (frequency cannot be estimated from the available data).
| System organ class | Frequency | Undesirable effects |
| Immune system disorders | Not Known | hypersensitivity reactions including rash, pruritus and oedema |
| Metabolism and nutrition | Not Known | excessive loss of weight |
| disorders | ||
| Nervous system disorders | Not Known | restlessness, excitability, tremor, insomnia |
| Cardiac disorders | Not Known | Anginal pain, cardiac arrhythmias, palpitations, tachycardia. |
| Gastrointestinal disorders | Not Known | Diarrhoea, vomiting |
| Musculoskeletal and connective tissue disorder | Not Known | muscle cramps, muscular weakness, |
| General disorders and administration site conditions | Not Known | headache, flushing, sweating, fever, heat intolerance |
| Skin and subcutaneous tissue disorders | Not Known | Transient hair loss 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. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme. Website: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.
4.9 Overdose
Symptoms
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
If the patient is seen within a few hours of overdosage: gastric lavage or emesis.
Treatment is symptomatic. Tachycardia in adults may be controlled with 40 mg propranolol every 6 hours.
5 PHARMACOLOGICAL PROPERTIES
5.1 Pharmacodynamic properties
Pharmacotherapeutic group: Thyroid preparations.
ATC code: H03AA02
Liothyronine sodium is a synthetic form of 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.
5.2 Pharmacokinetic properties
Absorption:
Liothyronine sodium is almost completely absorbed from the gastro-intestinal tract.
Distribution
Liothyronine sodium is almost completely absorbed from the gastro-intestinal tract. 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.
5.3 Preclinical safety data
No further relevant data.
6 PHARMACEUTICAL PARTICULARS
6.1 List of excipients
Calcium sulfate dihydrate
Corn starch
Gelatin
Magnesium stearate
Mannitol (E421)
6.2 Incompatibilities
Not applicable.
6.3 Shelf life
2 years
6.4 Special precautions for storage
Store in the original container in order to protect from light.
6.5 Nature and contents of container
High-density polyethylene (HDPE) container with a polypropylene child-resistant closure, with a 2 g canister containing silica gel and a cotton plug.
Pack sizes: 28 and 112 tablets. Not all pack sizes may be marketed.
6.6 Special precautions for disposal
Any unused medicinal product or waste material should be disposed of in accordance with local requirements.
7 MARKETING AUTHORISATION HOLDER
Pharmassist Limited
15 Anthrakorichon Street
Nea Ionia, GR-14235, Athens
Greece
8 MARKETING AUTHORISATION NUMBER(S)
PL 55524/0001
9 DATE OF FIRST AUTHORISATION/RENEWAL OF THE
AUTHORISATION
17/12/2021
10 DATE OF REVISION OF THE TEXT
28/05/2026