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