TRIOSTAT
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TRIOSTAT (TRIOSTAT).
TRIOSTAT (liothyronine sodium) is a synthetic form of the thyroid hormone triiodothyronine (T3). It binds to thyroid hormone receptors in the nucleus, altering gene expression and increasing cellular metabolism, oxygen consumption, and heat production.
| Metabolism | Metabolized primarily in the liver via deiodination (type I and II deiodinases) and conjugation (glucuronidation and sulfation). Minor metabolism via deamination and decarboxylation. CYP450 enzymes not significantly involved. |
| Excretion | Renal (40% unchanged, 20% as liothyronine conjugates); fecal (35%) |
| Half-life | 2.5 days (terminal); shortened in hyperthyroidism, prolonged in hypothyroidism |
| Protein binding | >99.7% bound to thyroxine-binding globulin, transthyretin, and albumin |
| Volume of Distribution | 0.2-0.4 L/kg (primarily distributes to liver and kidneys) |
| Bioavailability | Oral: 90-95% (well absorbed); IV: 100% |
| Onset of Action | IV: 2-4 hours (thyroid hormone replacement); Oral: 6-12 hours |
| Duration of Action | IV: 2-3 days; Oral: 1-2 weeks (clinical effects persist beyond serum half-life) |
| Molecular Weight | 672.96 |
Adult: 5 mcg/kg IV every 8 hours. Adjust based on clinical response.
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment required for renal impairment. |
| Liver impairment | No specific guidelines; use with caution in severe hepatic impairment. |
| Pediatric use | Weight-based: 0.5-1 mcg/kg IV every 8-12 hours. |
| Geriatric use | Start at lower end of dosing range, monitor thyroid function closely. |
| 1st trimester | Triostat (liothyronine) is not recommended for use in pregnancy, especially during the first trimester, due to risks of fetal hypothyroidism or hyperthyroidism if maternal thyroid status is not carefully controlled. However, if a mother is hypothyroid and requires thyroid hormone replacement, levothyroxine is preferred; liothyronine should only be used if necessary and under close monitoring. |
| 2nd trimester | During the second trimester, use of liothyronine may be considered if clearly indicated, but levothyroxine is generally preferred. Maternal thyroid function must be monitored to avoid fetal thyroid dysfunction. |
| 3rd trimester | In the third trimester, liothyronine may be used with caution if required, but levothyroxine remains the standard of care. Fetal thyroid development is underway, and maternal thyroid status should be maintained euthyroid. |
Clinical note
Comprehensive clinical and safety monograph for TRIOSTAT (TRIOSTAT).
| Placental transfer | Liothyronine (T3) crosses the placenta to a limited extent; however, placental transfer is less than that of levothyroxine (T4). But endogenous T3 crossing is regulated; exogenous T3 may still affect fetal thyroid function. |
■ FDA Black Box Warning
WARNING: In patients with cardiac disease, particularly angina pectoris or myocardial infarction, administration of TRIOSTAT may precipitate cardiac arrhythmias, myocardial ischemia, or infarction. Use with extreme caution.
| Serious Effects |
Uncorrected adrenal insufficiencyUntreated thyrotoxicosisAcute myocardial infarctionHypersensitivity to liothyronine or any component of the formulation
| Precautions | Cardiac toxicity: Risk of arrhythmias, myocardial infarction, and cardiac arrest, especially in elderly or patients with underlying heart disease., Thyrotoxic crisis: Overdose may cause symptoms of hyperthyroidism including tachycardia, palpitations, chest pain, diaphoresis, and tremors., Exacerbation of diabetes mellitus: May increase insulin or oral hypoglycemic requirements., Adrenal insufficiency: May precipitate acute adrenal crisis in patients with borderline adrenal function; treat with corticosteroids before initiating thyroid hormone., Osteoporosis: Long-term therapy with supraphysiologic doses may decrease bone mineral density. |
| Food/Dietary |
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| Breastfeeding | Liothyronine is excreted into breast milk in low amounts. Thyroid hormones are endogenous substances; exogenous liothyronine may increase the risk of neonatal hyperthyroidism if maternal dosage is high. Monitor infant thyroid function. Use with caution during breastfeeding only if clearly needed. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Pregnancy Category A. No evidence of fetal harm in first trimester; animal studies show no risk. Second and third trimesters: risk of maternal hypothyroidism may affect fetal neurodevelopment; monitor thyroid function. |
| Fetal Monitoring | Monitor maternal thyroid function tests (TSH, FT4) every 4-6 weeks during pregnancy. Assess fetal growth and development; consider umbilical blood sampling if signs of thyroid dysfunction. |
| Fertility Effects | No direct effects on fertility. Thyroid hormone replacement in hypothyroid women improves ovulation and pregnancy outcomes. Overtreatment or undertreatment may disrupt menstrual cycles. |
| No specific food interactions, but ensure consistent iodine intake. Avoid excessive soy, fiber, or iron supplements that may affect absorption of oral thyroid medications later. |
| Clinical Pearls | Triostat (liothyronine sodium) is intravenous T3 used for myxedema coma or severe hypothyroidism when rapid onset is needed. Monitor for cardiac ischemia, especially in elderly or those with coronary artery disease. Start with low doses (10-20 mcg IV) and titrate cautiously. Convert to oral levothyroxine once stable. |
| Patient Advice | Triostat is given intravenously in the hospital for severe hypothyroidism. · Report any chest pain, palpitations, or shortness of breath immediately. · You will be switched to an oral thyroid medication before discharge. · Do not stop other thyroid medications without your doctor's advice. · Regular blood tests will monitor your thyroid levels. |