Pharmacologic class: Hormone supplement
Therapeutic class: Thyroid hormone
Pregnancy risk category A
FDA Box Warning
Drug shouldn't be used alone or with other agents to treat obesity or weight loss. In euthyroid patients, doses within range of daily hormonal requirements are ineffective for weight loss. Larger doses may cause serious or life-threatening toxicity, particularly when given with sympathomimetic amines (such as those used for anorectic effects).
Regulates cell growth and differentiation and increases metabolic rate of body tissues; effects mediated at cellular level
Tablets: 15 mg, 30 mg, 60 mg, 90 mg, 120 mg, 180 mg, 240 mg, 300 mg
Indications and dosages
➣ Mild hypothyroidism
Adults: Initially, 60 mg/day P.O.; may increase by 60 mg q 30 days to desired response. Usual maintenance dosage is 60 to 180 mg/day.
➣ Severe hypothyroidism
Adults: Initially, 15 mg/day P.O. daily; may increase to 30 mg/day after 2 weeks and then to 60 mg/day 2 weeks later. Assess after 1 month, and again 1 month later at 60 mg-dose. If necessary, dosage may then increase to 120 mg/day P.O. for 2 months, with assessment repeated. Subsequent assessments and dosage increases may occur up to a maximum of 180 mg/day.
➣ Congenital or severe hypothyroidism
Children: Initially, 15 mg P.O. daily; may increase to 30 mg/day after 2 weeks, with subsequent increases at 2-week intervals. Maintenance dosage may be higher in growing children than in hypothyroid adults.
• Cardiovascular disease
• Elderly patients
• Hypersensitivity to drug or its components
• Adrenal insufficiency
Use cautiously in:
• tartrazine sensitivity (some products)
• cardiovascular disease
• elderly patients
• breastfeeding patients.
• Give before breakfast each day.
CNS: insomnia, tremors, headache
CV: palpitations, angina pectoris, hypertension, tachycardia, arrhythmias, cardiac arrest
GI: nausea, vomiting, diarrhea
GU: menstrual irregularities
Metabolic: heat intolerance, thyroid storm
Musculoskeletal: accelerated bone maturation (in children)
Other: weight loss, appetite changes, fever
Drug-drug. Anticoagulants, catecholamines, sympathomimetics: increased effects of these drugs
Bile acid sequestrants: decreased thyroid hormone absorption
Digoxin, insulin, oral hypoglycemics: decreased effects of these drugs
Estrogen: decreased thyroid hormone effects
Oral anticoagulants: increased risk of bleeding
Drug-diagnostic tests. Aspartate aminotransferase, creatine kinase, glucose, lactate dehydrogenase, protein-bound iodine: increased levels
Thyroid function tests: decreased values
Drug-herbs. Bugleweed, soy: increased adverse drug reactions
Monitor for chest pain. If it occurs, withhold drug and contact prescriber.
• Assess vital signs and temperature frequently.
Monitor thyroid function tests closely. Immediately report evidence of thyroid storm.
• In diabetic patient, monitor blood glucose level closely.
• In children, monitor sleeping pulse rate and morning basal temperature.
• In female on long-term therapy, monitor bone density tests.
• Tell patient to take each morning before breakfast.
Caution patient not to stop therapy abruptly. Dosage must be tapered.
Advise patient to immediately report chest pain or signs and symptoms of drug toxicity (fever, chest pain, rapid pulse, skipped heartbeats, heat intolerance, excessive sweating, nervousness, emotional instability).
• Instruct patient to tell all prescribers he's taking drug. Caution him not to use over-the-counter preparations without consulting prescriber.
• Tell diabetic patient that drug may alter blood glucose level. Encourage frequent glucose self-monitoring.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, and herbs mentioned above.