Thyronorm

# Thyronorm ## Overview - **Classification**: Thyroid hormone replacement - **Mechanism**: Synthetic L-thyroxine (T4) converted to triiodothyronine (T3) in the body, which regulates metabolism, growth, and development. ## Primary Indications 1. **Hypothyroidism**: Replacement therapy for all etiologies. 2. **TSH Suppression**: Adjunct to surgery and radioiodine in thyroid-dependent cancers. ## Adult Dosing ### Standard Dosing **Primary Hypothyroidism** - **Initial Dose (Young, otherwise healthy)**: **25-50 mcg** orally once daily. - **Initial Dose (Elderly, Cardiac Disease)**: **12.5-25 mcg** orally once daily. - **Maintenance Dose**: **1.6 mcg/kg/day** orally once daily. - Average: **100-125 mcg** orally once daily. - **Frequency**: Once daily. - **Route**: Oral. - **Duration**: Lifelong therapy usually required. **TSH Suppression (Thyroid Cancer)** - **Dose**: Typically **2.0-2.7 mcg/kg/day** orally. - Adjust to maintain target TSH level based on cancer risk. - **Frequency**: Once daily. - **Route**: Oral. ### Dose Adjustments - **Renal Impairment**: No specific dose adjustment generally needed. - **Hepatic Impairment**: No specific dose adjustment generally needed. - **Elderly Patients**: Start at a lower dose (**12.5-25 mcg/day**) due to increased risk of cardiac adverse effects. Titrate slowly. ## Pediatric Dosing ### Neonates (0-28 days) - **Indication**: Congenital Hypothyroidism. - **Dose**: **10-15 mcg/kg/day** orally. - **Frequency**: Once daily. - **Maximum**: **50 mcg/day**. - **Special Notes**: Crushed tablet can be mixed with small amount of breast milk/water and given by spoon/syringe immediately. ### Infants (1-12 months) - **Dose**: **6-8 mcg/kg/day** orally. - **Frequency**: Once daily. - **Maximum**: **75 mcg/day**. ### Children (1-5 years) - **Dose**: **5-6 mcg/kg/day** orally. - **Frequency**: Once daily. - **Maximum**: **100-125 mcg/day**. ### Children (6-12 years) - **Dose**: **4-5 mcg/kg/day** orally. - **Frequency**: Once daily. - **Maximum**: **150-175 mcg/day**. ### Adolescents (13-18 years) - **Dose**: **2-3 mcg/kg/day** orally, titrate to TSH target. - **Maximum**: Adult replacement dose (**~200 mcg/day**). ## Safety Information ### Contraindications - **Absolute**: Acute myocardial infarction. - **Absolute**: Untreated adrenal cortical insufficiency. - **Absolute**: Untreated thyrotoxicosis. - **Absolute**: Hypersensitivity to levothyroxine or excipients. ### Common Adverse Effects - **Very Common (>10%)**: Palpitations, tachycardia, tremor, headache, insomnia, nervousness, sweating. (Often signs of overdose). - **Common (1-10%)**: Weight loss, diarrhea, heat intolerance, transient hair loss (in children during initial months). - **Serious but Rare**: Arrhythmias, angina pectoris, myocardial infarction (especially in elderly/cardiac disease with too rapid titration). ### Key Drug Interactions - **Calcium, Iron, Aluminum/Magnesium Antacids, PPIs**: Decrease levothyroxine absorption. Separate by **4 hours**. - **Warfarin**: May enhance anticoagulant effect. Monitor INR closely. - **Estrogens, Oral Contraceptives**: May increase levothyroxine requirement. Monitor TSH. - **Anticonvulsants (phenytoin, carbamazepine), Rifampin**: Increase levothyroxine metabolism. May need higher dose. ## Monitoring & Follow-up - **Before Treatment**: Baseline TSH, Free T4. Consider ECG in elderly or those with cardiac risk factors. - **During Treatment**: TSH levels every **4-6 weeks** until stable, then annually. - **Clinical Signs**: Monitor for symptoms of hypo- or hyperthyroidism (fatigue, weight gain, anxiety, palpitations). ## Clinical Pearls - 💡 Take on an empty stomach, ideally **30-60 minutes before breakfast** with water. - 💡 Maintain **consistent timing** of administration daily. - 💡 Administer interacting drugs (calcium, iron) at least **4 hours apart** from levothyroxine. - 💡 Brand consistency is recommended due to narrow therapeutic index; avoid switching brands without careful monitoring. - 💡 This is usually a **lifelong therapy**; do not discontinue abruptly. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.