Class: Thyroid Supplement
Dosage Forms. Tablet: 15 mg, 16.25 mg, 30 mg, 32.4 mg, 32.5 mg, 48.75 mg, 60 mg, 64.8 mg, 65 mg, 81.25 mg, 90 mg, 97.5 mg, 113.75 mg, 120 mg, 130 mg, 146.25 mg, 162.5 mg, 180 mg, 195 mg, 240 mg, 260 mg, 300 mg, 325 mg
Common FDA Label Indication, Dosing, and Titration.
1. Hypothyroidism: Dosing individualized based on clinical response and serum TSH levels; Children birth to 6 mo, 4.8-6.8 mg/kg/d po daily; Children 6-12 mo, 3.6-4.8 mg/kg/d po daily; Children 1-5 y, 3-3.6 mg/kg/d po daily; Children 6-12 y, 2.4-3 mg/kg/d po daily; Children over 12 y, 1.2-1.8 mg/kg/d po daily; Adults, 60-120 mg po daily
Off-Label Uses. None
MOA. Thyroid hormone is a naturally derived thyroid replacement containing both levothyroxine (T4) and liothyronine (T3). The endogenous thyroid hormones, T3 and T4, diffuse into the cell nucleus and bind to thyroid receptor proteins attached to DNA. This hormone nuclear receptor complex activates gene transcription and synthesis of messenger RNA and cytoplasmic proteins.
Drug Characteristics: Thyroid
Medication Safety Issues: Thyroid
Drug Interactions: Thyroid
Adverse Reactions: Thyroid
Efficacy Monitoring Parameters. Serum TSH, T3, and T4 levels: resolution of symptoms of hypothyroidism, fatigue, edema, hair loss, cold intolerance, lethargy
Toxicity Monitoring Parameters. Monitor patients with preexisting cardiovascular disease for exacerbation of symptoms.
Key Patient Counseling Points. You may have to take this medicine for 6-8 wk before your symptoms improve. Do not stop using this medicine suddenly without asking your doctor. You may need to slowly decrease your dose before stopping it completely. Take on an empty stomach, with water.
Clinical Pearls. T3 normal range is 100-200 ng/dL. T4 normal range is 4.5-11.2 mcg/dL. TSH level should be between 0.5 and 3.0 mIU/L in those successfully treated for a thyroid disorder. When used for weight loss, high doses may cause life-threatening adverse effects.