Levothyroxine Sodium is a synthetic, levo-isomer of thyroxine (T4), identical to the endogenous hormone produced by the human thyroid gland. It is the standard of care for thyroid hormone replacement therapy in hypothyroidism. The 88mcg strength is a commonly prescribed maintenance dose for many adults, requiring precise dosing based on clinical and biochemical response.
Adult: For newly diagnosed hypothyroidism in healthy adults <50-60 years: Start 1.6 mcg/kg/day (approx 100-125 mcg/day). Maintenance dose is highly individualized; 88 mcg is a common maintenance dose. Dose adjusted based on TSH levels every 6-8 weeks until stable. For TSH suppression in thyroid cancer: doses >2 mcg/kg/day often required.
Note: Take on an empty stomach, at least 30-60 minutes before breakfast, with a full glass of water. Maintain consistent timing daily. Avoid concomitant intake of calcium, iron, antacids, proton pump inhibitors, bile acid sequestrants, and high-fiber foods by at least 4 hours. Soy products and coffee can also interfere.
Levothyroxine sodium replaces endogenous thyroxine (T4). It is a prohormone that is converted peripherally to the active hormone triiodothyronine (T3) by deiodinase enzymes. T3 and T4 bind to nuclear thyroid hormone receptors (TRα and TRβ), which then bind to thyroid hormone response elements (TREs) on DNA, regulating gene transcription. This increases basal metabolic rate, protein synthesis, and affects growth and development.
Pregnancy: CRITICAL: Requirement increases by 25-50% (often by 25-50 mcg/day) as early as 4-6 weeks gestation. Monitor TSH every 4 weeks in first trimester, and at least once per trimester thereafter. Goal TSH: trimester-specific (e.g., <2.5 mIU/L in first trimester). Return to pre-pregnancy dose post-delivery. Safe in pregnancy (Category A).
Driving: Hypothyroidism itself can impair cognitive function and reflexes. Once euthyroid, no restrictions. Over-replacement may cause nervousness and tremor, potentially affecting driving.
| Calcium Carbonate / Iron Supplements | Decreased absorption of levothyroxine | Major |
| Proton Pump Inhibitors (Omeprazole) | Decreased absorption due to altered gastric pH | Moderate |
| Cholestyramine, Colestipol | Binding and decreased absorption | Major |
| Phenytoin, Carbamazepine, Rifampicin | Increased hepatic metabolism of levothyroxine, requiring dose increase | Moderate |
| Amiodarone | Can cause both hypothyroidism or hyperthyroidism; frequent monitoring needed | Major |
| Warfarin | Increased anticoagulant effect; monitor INR closely | Major |
| Oral Contraceptives, Estrogens | Increase thyroxine-binding globulin (TBG), may require dose adjustment | Moderate |
| Beta-blockers (e.g., Propranolol) | Decreased conversion of T4 to T3 (high doses) | Minor |
| Antidiabetics (Insulin, Sulfonylureas) | Levothyroxine may increase blood glucose; adjust antidiabetic dose | Moderate |
Same composition (Thyroxine (88mcg)), different brands: