Monograph Details
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Endocrine System
> Thyroid disease
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SYNTHROID |
| Manufacturer |
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Abbott Laboratories |
| Legal Classification |
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Rx
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| Pharmacological Class |
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T4 (synthetic). |
| Generic Name |
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Levothyroxine sodium 25micrograms, 50micrograms (dye-free), 75micrograms, 88micrograms, 100micrograms, 112micrograms, 125micrograms, 137micrograms, 150micrograms, 175micrograms, 200micrograms, 300micrograms; scored tabs. |
| Also |
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• SYNTHROID INJECTION
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| Indications |
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Hypothyroidism. |
| Children |
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Give once daily on empty stomach. May crush tabs and mix in 5–10mL water. Hypothyroidism: 0–3months: 10–15micrograms/kg per day; 3–6months: 8–10micrograms/kg per day; 6–12months: 6–8micrograms/kg per day; 1–5yrs: 5–6micrograms/kg per day; 6–12yrs: 4–5micrograms/kg per day; >12yrs: 2–3micrograms/kg per day; growth and puberty complete: as adult. Chronic or severe hypothyroidism: initially 25micrograms/day; titrate in increments of 25micrograms every 4weeks. Infants with serum T4<5mcg/dL: initially 50micrograms/day. |
| Adults |
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Take in AM on empty stomach. Hypothyroidism: 1.7micrograms/kg once daily. >50yrs, or <50yrs with cardiovascular disease: initially 25–50micrograms once daily; titrate in increments of 12.5–25micrograms every 6–8 weeks. Elderly with cardiovascular disease: initially 12.5–25micrograms once daily; titrate in increments of 12.5–25micrograms every 4–6 weeks. Usual max 200micrograms/day. Severe hypothyroidism: initially 12.5–25micrograms once daily; titrate in increments of 25micrograms/day every 4 weeks. Subclinical hypothyroidism, secondary or tertiary hypothyroidism: see literature. |
| Contraindications |
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Uncorrected adrenal insufficiency. Untreated thyrotoxicosis. Acute MI. |
| Precautions |
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Not for treatment of obesity or infertility. Cardiovascular disease. Seizures. Adrenocortical insufficiency. Increased sensitivity in severe hypothyroidism. Autonomous thyroid tissue. Elderly. Pregnancy (Cat. A); do not discontinue due to pregnancy. Nursing mothers. |
| Interactions |
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See literature. Absorption reduced by some foods (e.g., soy, fiber), aluminum and magnesium hydroxide, simethicone, calcium carbonate, sodium polystyrene sulfonate, bile acid sequestrants, iron, sucralfate (give at least 4 hrs apart). Potentiates, and is potentiated by, tri- and tetracyclic antidepressants, sympathomimetics. Antagonized by hepatic enzyme inducers (e.g., carbamazepine, phenytoin, phenobarbital, rifampin), sertraline. Antagonizes digoxin. Marked hypertension and tachycardia with ketamine. Estrogens affect thyroid function tests. Monitor oral anticoagulants, antidiabetic agents, theophylline. |
| Adverse Reactions |
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Hyperthyroidism, decreased bone mineral density, transient alopecia; seizures (rare); pseudotumor cerebri in children. |
| How Supplied |
Tabs—100, 1000
Single dose vials (10mL)—1 |
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