Thyroid, Desiccated (Thyroid USP)

A to Z Drug Facts

 Action Increases metabolic rate of body tissues.

 Indications Replacement or supplemental therapy in hypothyroidism; TSH suppression (in thyroid cancer, nodules, goiters and enlargement in chronic thyroiditis); iagnostic agent to differentiate suspected hyperthyroidism from euthyroidism.

 Contraindications Hypersensitivity to any ingredient; acute MI and thyrotoxicosis uncomplicated by hypothyroidism. Also contraindicated when hypothyroidism and hypoadrenalism (Addison's disease) coexist, unless treatment of hypoadrenalism with adrenocortical steroids precedes initiation of thyroid therapy.

 Route/Dosage

Optimal dosage determined by clinical response and laboratory findings.

Hypothyroidism

ADULTS: PO 30 mg/day initially, increasing by 15 mg increments every 2–3 wk. In patients with long-standing myxedema, 15 mg/day, particularly if cardiovascular impairment is suspected. Reduce dosage if angina occurs. Maintenance: 60–120 mg/day. CHILDREN: PO See table for recommended dose in congenital hypothyroidism.

Thyroid Cancer

Larger doses required.

 Interactions

Anticoagulants: Anticoagulant effects may be increased. Cholestyramine: May decrease thyroid efficacy. Digitalis glycosides: Digitalis levels may increase, resulting in toxicity. Theophyllines: Theophylline clearance may be altered in hyperthyroid or hypothyroid patients.

 Lab Test Interferences Consider changes in thyroid-binding globulin concentration when interpreting T₄ and T₃ values. Medicinal or dietary iodine interferes with all in vivo tests of radioiodine uptake, producing low uptakes that may not reflect true decrease in hormone synthesis.

 Adverse Reactions

OTHER: Adverse reactions generally indicate hyperthyroidism due to therapeutic overdosage. CV: Palpitations; tachycardia; cardiac arrhythmias; angina pectoris; ardiac arrest. CNS: Tremors; headache; nervousness; insomnia. GI: Diarrhea; vomiting. GU: Menstrual irregularities. OTHER: Hypersensitivity; weight loss; sweating; heat intolerance; fever.

 Precautions

Pregnancy: Category A. Lactation: Excreted in breast milk. Children: Congenital hypothyroidism: Routine determinations of serum T₄ r TSH are strongly advised in neonates. Initiate treatment immediately on diagnosis and continue for life, unless transient hypothyroidism is suspected. In infants, excessive doses of thyroid hormone preparations may produce craniosynostosis. Children may experience transient partial hair loss in first few months of thyroid therapy. Cardiovascular disease: Use caution when integrity of CV system, particularly coronary arteries is suspect (eg, angina, elderly). Development of chest pain or worsening CV disease requires decrease in dosage. Observe patients with coronary artery disease during surgery, since possibility of cardiac arrhythmias may be greater in those treated with thyroid hormones. Endocrine disorders: Therapy in patients with concomitant diabetes mellitus or insipidus or adrenal insufficiency (Addison's disease) exacerbates intensity of symptoms. Therapy of myxedema coma requires simultaneous administration of glucocorticoids. In patients whose hypothyroidism is secondary to hypopituitarism, adrenal insufficiency, if present, should be corrected with corticosteroids before administering thyroid hormones. Hyperthyroid effects: May rarely precipitate hyperthyroid state or may aggravate existing hyperthyroidism. Morphologic hypogonadism and nephrosis: Rule out before therapy. Myxedema: Patients are particularly sensitive to thyroid preparations. Begin with small doses. Obesity: Should not be used for weight reduction; may produce serious or even life-threatening toxicity in larger doses, particularly when given with anorexiants.

 Administration/Storage

• Assess baseline T₄ or TSH as ordered by physician.
• When administered as single dose, give in morning to avoid sleeplessness.
• Adjust dose to administer lowest dose possible to relieve symptoms.
• Do not interchange different thyroid products. Absorption may vary.
• Store at room temperature in tightly closed container.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies.
• Before each dose, assess BP and pulse.
• Monitor vital signs and weight.
• In children, monitor height and weight to document normal growth rate.
• Notify physician of any changes from baseline status in physical assessment or laboratory testing.

 Patient/Family Education

• Explain that children may have short-term temporary hair loss at start of therapy.
• Tell patient to report fever, weight loss, menstrual irregularity, palpitations, chest pain, headache, faint feeling, sweatiness, diarrhea, vomiting, inability to sleep, excitability, irritability, anxiety, nervousness or any changes to physician.
• Teach patient to avoid otc preparations and food with iodine: odinated salt, soy beans, tofu, turnips, some seafood, some types of bread.
• Instruct patient not to switch drug brands unless physician approves.

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Copyright © 2003 Facts and Comparisons
David S. Tatro
A to Z Drug Facts