LIOTHYRONINE SODIUM (T3)

LIOTHYRONINE SODIUM (T3)
(lye-oh-thye'roe-neen)
Cytomel, Triostat
Classifications: hormone; thyroid hormone replacement;
Therapeutic: thyroid hormone replacement

Prototype: Levothyroxine sodium
Pregnancy Category: A

Availability

5 mcg, 25 mcg, 50 mcg tablets; 10 mcg/mL injection

Action

Synthetic form of natural thyroid hormone (T3). Shares actions and uses of thyroid but has more rapid action and more rapid disappearance of effect, permitting quick dosage adjustment, if necessary.

Therapeutic Effect

Replacement therapy for absent or decreased thyroid hormone. Principal effect is an increase in the metabolic rate of all body tissues.

Uses

Replacement or supplemental therapy for cretinism, myxedema, goiter, secondary (pituitary) or tertiary (hypothalamic) hypothyroidism, and T3 suppression test.

Contraindications

Hypersensitivity to liothyronine; thyrotoxicosis; obesity treatment; severe cardiovascular conditions, acute MI, uncontrolled hypertension; adrenal insufficiency.

Cautious Use

Angina pectoris, hypertension; diabetes mellitus; impaired kidney function, renal failure; older adult; pregnancy (category A), lactation.

Route & Dosage

Thyroid Replacement
Adult: PO 25–75 mcg/d
Geriatric: PO 5 mcg/d, increase by 5 mcg/d every 1–2 wk
Child: PO 5 mcg/d gradually increased by 5 mcg/d q3–4d until desired response

Myxedema
Adult: PO 5–100 mcg/d IV 25–50 mcg, may repeat between 4 and 12 h after previous dose. Target dose >65 mcg/d (max: 100 mcg/d).
Geriatric: PO Start at 5 mcg/d

Goiter
Adult: PO 5–75 mcg/d
Geriatric: PO Start at 5 mcg/d
Child: PO 5 mcg/d, increase by 5 mcg q1–2 wk (usual maintenance dose 15–20 mcg/d)

T3 Suppression Test
Adult: PO 75–100 mcg/d x 7 d

Administration

Oral
  • Give daily before breakfast.
  • Discontinue other thyroid drug when changing to liothyronine; initiate liothyronine at low dosage with gradual increases according to patient's response.
Intravenous

PREPARE: Direct: Give undiluted.  

ADMINISTER: Direct: Give each 10 mcg or fraction thereof over 1 min.  

  • Store tablets in heat-, light-, and moisture-proof container.

Adverse Effects (≥1%)

Endocrine: Result from overdosage evidenced as S&S of hyperthyroidism (see Appendix F). Musculoskeletal: Accelerated rate of bone maturation in children.

Interactions

Drug: Cholestyramine, colestipol decrease absorption; epinephrine, norepinephrine increase risk of cardiac insufficiency; oral anticoagulants may potentiate hypoprothrombinemia.

Pharmacokinetics

Absorption: Completely absorbed from GI tract. Peak: 24–72 h. Duration: Up to 72 h. Distribution: Gradually released into tissue cells. Half-Life: 6–7 d.

Nursing Implications

Assessment & Drug Effects

  • Watch for possible additive effects during the early period of liothyronine substitution for another preparation, particularly in older adults, children, and patients with cardiovascular disease. Residual actions of other thyroid preparations may persist for weeks.
  • Metabolic effects of liothyronine persist a few days after drug withdrawal.
  • Withhold drug for 1–2 d at onset of overdosage symptoms (hyperthyroidism, see Appendix F); usually therapy can be resumed with lower dosage.

Patient & Family Education

  • Take medication exactly as ordered.
  • Learn S&S of hyperthyroidism (see Appendix F); notify physician promptly if they appear.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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