Dosing and uses of Cytomel, Triostat (liothyronine)
Adult dosage forms and strengths
injectable solution
- 10mcg/mL
tablet
- 5mcg
- 25mcg
- 50mcg
Hypothyroidism
Initial: 25 mcg PO qDay; may increase by 25 mcg q1-2Weeks; not to exceed 100 mcg/day
Maintenance: 25-75 mcg PO qDay
May use 10-12.5 mcg T3 in combo with T4 (decrease T4 dose by 50 mcg)
Nontoxic Goiter
Initial: 5 mcg PO qDay; may increase by 5-10 mcg q1-2Weeks (5 mcg in elderly)
When reach 25 mcg PO qDay, may increase by 12.5 mcg or 25 mcg q1-2Weeks
Maintenance: 75 mcg PO qDay
Myxedema
Initial: 5 mcg PO qDay; may increase by 5-10 mcg/day q1-2Weeks
When reach 25 mcg PO qDay, may increase by 5-25 mcg q1-2Weeks
Maintenance: 50-100 mcg PO qDay
Myxedema Coma
Initial: 25-50 mcg IV
Patients with CVD: 10-20 mcg IV
Doses of at least 65 mcg/day IV associated with lower mortality
Allow 4-12 hr between doses; not to exceed 12 hours
Pediatric dosage forms and strengths
injectable solution
- 10mcg/mL
tablet
- 5mcg
- 25mcg
- 50mcg
Congenital Hypothyroidism
Initial: 5 mcg PO qDay; may increase by 5 mcg q3-4Days
Maintenance
- <1 year: 20 mcg PO qDay
- 1-3 years: 50 mcg PO qDay
- >3 years: 25-75 mcg PO qDay
Nontoxic Goiter
Initial: 5 mcg PO qDay; may increase by 5-10 mcg q1-2Weeks
When reach 25 mcg PO qDay, may increase by 12.5 mcg or 25 mcg q1-2Weeks
Maintenance: 75 mcg PO qDay
Geriatric dosage forms and strengths
5 mcg/day PO; may increase by 5 mcg/day q2Weeks
Cytomel, Triostat (liothyronine) adverse (side) effects
1-10%
Tachycardia (3%)
Hypotension (2%)
Myocardial infarction (2%)
Cardiopulmonary arrest (2%)
<1%
Congestive heart failure
Hypertension
Twitching
Phlebitis
Angina
Fever
Warnings
Black box warnings
Thyroid hormones, either alone or with other therapeutic agents, should not be used for the treatment of obesity or for weight loss
In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction; larger doses may produce serious or even life-threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines, such as those used for their anorectic effects.
Contraindications
Hypersensitivity to thyroid hormone
Acute MI uncomplicated by hypothyroidism, thyrotoxicosis, untreated adrenal insufficiency
Treatment of obesity or infertility
Cautions
Caution in angina, cardiovascular disease, hypopituitarism, Dm
May use judiciously in acute MI caused/complicated by hypothyroidism
Perform periodic assessment of thyroid status when using as thyroid replacement
Myxedematous patients are very sensitive to thyroid hormone; start at very low dose
Pregnancy and lactation
Pregnancy category: A
Lactation: Excreted into breast milk; use caution
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Cytomel, Triostat (liothyronine)
Mechanism of action
A synthetic form of natural T3 hormone with same actions as natural product; thyroid hormone raises basal metabolic rate, increases utilization and mobilization of glycogen store, and promotes gluconeogenesis
Absorption
95% absorption
Onset: 2-4 hr
Duration: Several days (hypothyroidism)
Peak plasma time: PO: 1-2 hr
Max response: 2-3 days
Distribution
Protein bound: 99.7%, but not firmly
Metabolism
Hepatic, to deiodinated and conjugated metabolites
Elimination
Half-life: 2.5 days
Excretion: Urine, feces
Administration
IV Administration
Administer q4hr; no more than 12 hr apart
