liothyronine sodium: clinical use

Prescribing considerations

• For hypothyroidism, NHS initiation should normally be by a consultant endocrinologist after persistent symptoms on levothyroxine have been reviewed.
• Do not withdraw established treatment abruptly; specialist-led withdrawal should be gradual.
• Assess adrenal function where insufficiency is suspected and establish corticosteroid replacement before thyroid hormone.
• Use particular caution in older people, long-standing hypothyroidism, diabetes and patients with cardiovascular risk.
• Review thyroid status and symptoms after a formulation or product change because bioavailability may differ.

Contraindications and cautions

• Hypersensitivity to liothyronine or formulation excipients.
• Thyrotoxicosis, except where specifically used as part of the licensed block-and-replace context.
• Angina, established myocardial ischaemia or other cardiovascular disease as specified by the individual product.
• Check formulation-specific excipients, including lactose in a selected tablet, gelatin in capsules, preservative in the oral solution and dextran in the injection.

Monitoring

• TSH and clinical features of under- or over-replacement.
• Baseline and periodic cardiovascular assessment, including ECG where cardiac risk is relevant.
• Blood glucose in people with diabetes.
• Anticoagulation control where relevant.
• Bone risk during sustained over-replacement.
• Possible biotin interference when thyroid results do not fit the clinical picture.

Clinical pharmacology

Liothyronine is synthetic L-triiodothyronine. It is almost completely absorbed orally, is less protein-bound than thyroxine and has a faster onset and shorter persistence of effect.

Formulation and product differences

• The oral solution is supplied with an oral syringe and is compatible with specified medium and large feeding tubes; it contains sodium methyl parahydroxybenzoate.
• A selected tablet contains lactose and may be crushed and dispersed in water when necessary.
• A selected hard capsule contains gelatin and may be opened into water for patients unable to swallow it whole.
• The injectable product is a freeze-dried preparation for reconstitution, single use and intravenous administration in hospital; it contains dextran.

Capsule

Route: Oral

Strengths: 5 micrograms, 10 micrograms, 20 micrograms

Oral solution

Route: Oral

Strengths: 10 micrograms/mL