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Pronunciation

THYE-royd

Classifications

Therapeutic Classification: hormones

Pharmacologic Classification: thyroid preparations

Indications

BEERS REMS


Action

  • Replacement of or supplementation to endogenous thyroid hormones.
  • Principal effect is increasing metabolic rate of body tissues:
    • Promote gluconeogenesis,
    • Increase utilization and mobilization of glycogen stores,
    • Stimulate protein synthesis,
    • Promote cell growth and differentiation,
    • Aid in the development of the brain and CNS.
  • Contains T3 (triiodothyronine) and T4 (thyroxine) activity.
Therapeutic effects:
  • Replacement in deficiency states with restoration of normal hormonal balance.

Pharmacokinetics

Absorption: Levothyroxine is variably (50–80%) absorbed from the GI tract. Liothyronine is well absorbed.

Distribution: Distributed into most body tissues.

Metabolism/Excretion: Metabolized by the liver and other tissues. Thyroid hormone undergoes enterohepatic recirculation and is excreted in the feces via the bile.

Half-Life: T3 (liothyronine): 1–2 days; T4 (thyroxine): 6–7 days.

Time/Action Profile

ROUTEONSETPEAKDURATION
Levothyroxine POunknown1–3 wk1–3 wk
Liothyronine POunknown24–72 hr72 hr





Contraind./Precautions

Contraindicated in:

Use Cautiously in:

Adv. Reactions/Side Effects

Usually only seen when excessive doses cause iatrogenic hyperthyroidism

CV: arrhythmias, angina pectoris, tachycardia

GI: abdominal cramps, diarrhea, vomiting

Derm: hyperhidrosis

Endo: hyperthyroidism, menstrual irregularities

Metab: heat intolerance, weight loss

MS: accelerated bone maturation in children

Neuro: headache, insomnia, irritability

Interactions

Drug-drug:

Route/Dosage

Hypothyroidism

Availability

Assessment

Lab Test Considerations:

Toxicity and Overdose:

Implementation

Patient/Family Teaching

Evaluation/Desired Outcomes

US Brand Names

Adthyza, Armour Thyroid