TELITHRO 100

Indications

• Hypothyroidism
• Myxedema coma (as part of emergency treatment)
• Thyroid cancer (suppression therapy)
• Goiter (to reduce size)

Dosage

Children: Refer to the BNF for Children for appropriate dosing based

Adults: Refer to the BNF for specific dosing regimens based on individual patient needs and response.

Mechanism of action

Levothyroxine acts by replacing or supplementing the naturally occurring thyroid hormones in the body. It binds to thyroid hormone receptors in the nucleus of cells, leading to the regulation of gene expression and increased synthesis of proteins involved in metabolism. The drug influences various metabolic processes, including carbohydrate metabolism, protein synthesis, and lipolysis, thereby enhancing metabolic rate and promoting growth and development.

Pharmacodynamics

The pharmacodynamic effects of levothyroxine include increased basal metabolic rate, enhanced oxygen consumption, and stimulation of metabolic processes in various tissues. It has effects on carbohydrate metabolism, promoting gluconeogenesis and glycogenolysis, and influences lipid metabolism by increasing lipolysis. Levothyroxine also plays a crucial role in normal growth, development, and differentiation of tissues, particularly in the central nervous system and skeletal system during childhood.

Pharmacokinetics

Levothyroxine is well-absorbed from the gastrointestinal tract, with peak serum concentrations typically reached within 2 to 4 hours after oral administration. It has a long half-life, averaging 7 days, allowing for once-daily dosing. Levothyroxine is highly protein-bound, predominantly to thyroxine-binding globulin (TBG), albumin, and transthyretin. The drug undergoes conversion to its active metabolite, triiodothyronine (T3), in peripheral tissues, where it exerts its biological effects. Elimination occurs primarily through hepatic metabolism and renal excretion.

Contra-indications

• Untreated thyrotoxicosis
• Acute myocardial infarction
• Adrenal insufficiency
• Hypersensitivity to levothyroxine or any of its excipients

Adverse effects

• Hyperthyroidism
• Cardiac arrhythmias
• Palpitations
• Increased appetite
• Weight loss
• Heat intolerance
• Excessive sweating
• Menstrual irregularities
• Anxiety
• Insomnia

Interactions

• Antacids may reduce absorption
• Calcium supplements may interfere with absorption
• Iron supplements may reduce absorption
• Warfarin may have increased anticoagulant effect
• Certain antidepressants may increase levothyroxine requirements

Precautions

• Patients with cardiovascular disease should be monitored closely
• Thyroid function tests should be performed regularly
• Adjustments in dosage may be necessary for elderly patients
• Monitor for signs of hyperthyroidism

Pregnancy

Levothyroxine is generally considered safe during pregnancy. Dosage adjustments may be necessary as pregnancy progresses, and thyroid function should be monitored.

Breast-feeding

Levothyroxine is excreted in breast milk, but at therapeutic doses, it is not expected to harm a nursing infant. Monitor for any signs of adverse effects in the infant.

Storage

Store in a cool, dry place away from light. Keep out of reach of children.

Formulations

• Tablets
• Oral solution
• Injection