section name header

Pronunciation

THYE-royd

Classifications

Therapeutic Classification: hormones

Pharmacologic Classification: thyroid preparations

Indications

BEERS REMS

Action

Therapeutic Effects:

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:

Drug-Food:

Route/Dosage

Each 1 grain = 60 mg and is equivalent to approximately 100 mcg of levothyroxine (T4) or 25 mcg of liothyronine (T3)

Hypothyroidism

Availability

Assessment

Lab Test Considerations: Toxicity and Overdose:

Implementation

Patient/Family Teaching

Evaluation/Desired Outcomes

US Brand Names

Adthyza, Armour Thyroid