Addition of liothyronine sodium therapy in patients with diabetes mellitus may worsen glycemic control and result in increased antidiabetic agent or insulin requirements. Carefully monitor glycemic control, especially when liothyronine sodium is started, changed, or discontinued [see Warnings and Precautions (5.5)].
Liothyronine sodium increases the response to oral anticoagulant therapy. Therefore, a decrease in the dose of anticoagulant may be warranted with correction of the hypothyroid state or when the liothyronine sodium dose is increased. Closely monitor coagulation tests to permit appropriate and timely dosage adjustments.
Liothyronine sodium may reduce the therapeutic effects of digitalis glycosides. Serum digitalis glycoside levels may be decreased when a hypothyroid patient becomes euthyroid, necessitating an increase in the dose of digitalis glycosides.
Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and liothyronine sodium may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. Toxic effects may include increased risk of cardiac arrhythmias and central nervous system stimulation. Liothyronine sodium may accelerate the onset of action of tricyclics. Administration of sertraline in patients stabilized on liothyronine sodium may result in increased liothyronine sodium requirements.
Concurrent use of ketamine and liothyronine sodium may produce marked hypertension and tachycardia. Closely monitor blood pressure and heart rate in these patients.
Concurrent use of sympathomimetics and liothyronine sodium may increase the effects of sympathomimetics or thyroid hormone. Thyroid hormones may increase the risk of coronary insufficiency when sympathomimetic agents are administered to patients with coronary artery disease.
Concurrent use of tyrosine-kinase inhibitors such as imatinib may cause hypothyroidism. Closely monitor TSH levels in such patients.
Consider changes in TBG concentration when interpreting T4 and T3 values. Measure and evaluate unbound (free) hormone in this circumstance. Pregnancy, infectious hepatitis, estrogens, estrogen-containing oral contraceptives, and acute intermittent porphyria increase TBG concentrations. Nephrosis, severe hypoproteinemia, severe liver disease, acromegaly, androgens and corticosteroids decrease TBG concentration. Familial hyper- or hypo-thyroxine binding globulinemias have been described, with the incidence of TBG deficiency approximating 1 in 9000.
Experience with liothyronine use in pregnant women, including data from post-marketing studies, have not reported increased rates of major birth defects or miscarriages (see Data). There are risks to the mother and fetus associated with untreated hypothyroidism in pregnancy. Since TSH levels may increase during pregnancy, TSH should be monitored and liothyronine sodium dosage adjusted during pregnancy (see Clinical Considerations). There are no animal studies conducted with liothyronine during pregnancy. Liothyronine sodium should not be discontinued during pregnancy and hypothyroidism diagnosed during pregnancy should be promptly treated.
The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively.
Disease-associated maternal and/or embryo/fetal risk
Maternal hypothyroidism during pregnancy is associated with a higher rate of complications, including spontaneous abortion, gestational hypertension, pre-eclampsia, stillbirth, and premature delivery. Untreated maternal hypothyroidism may have an adverse effect on fetal neurocognitive development.
Dose adjustments during pregnancy and the postpartum period
Pregnancy may increase liothyronine sodium requirements. Serum TSH levels should be monitored and the liothyronine sodium dosage adjusted during pregnancy. Since postpartum TSH levels are similar to preconception values, the liothyronine sodium dosage should return to the pre-pregnancy dose immediately after delivery [see Dosage and Administration (2.3)].
Liothyronine is approved for use as a replacement therapy for hypothyroidism. Data from post-marketing studies have not reported increased rates of fetal malformations, miscarriages, or other adverse maternal or fetal outcomes associated with liothyronine use in pregnant women.
Limited published studies report that liothyronine is present in human milk. However, there is insufficient information to determine the effects of liothyronine on the breastfed infant and no available information on the effects of liothyronine on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for liothyronine sodium and any potential adverse effects on the breastfed infant from liothyronine sodium or from the underlying maternal condition.
The initial dose of liothyronine sodium varies with age and body weight. Dosing adjustments are based on an assessment of the individual patient’s clinical and laboratory parameters [see Dosage and Administration (2.3, 2.4)].
In pediatric patients in whom a diagnosis of permanent hypothyroidism has not been established, discontinue thyroid hormone for a trial period, but only after the child is at least 3 years of age. Obtain serum TSH, T4, and T3 levels at the end of the trial period, and use laboratory test results and clinical assessments to guide diagnosis and treatment, if warranted [see Dosage and Administration (2.6)].
Rapid restoration of normal serum T4 concentrations is essential for preventing the adverse effects of congenital hypothyroidism on intellectual development as well as on overall physical growth and maturation. Therefore, initiate thyroid hormone immediately upon diagnosis. Thyroid hormone is generally continued for life in these patients.
Closely monitor infants during the first 2 weeks of thyroid hormone therapy for cardiac overload, arrhythmias, and aspiration from avid suckling.
Closely monitor patients to avoid undertreatment or overtreatment. Undertreatment may have deleterious effects on intellectual development and linear growth. Overtreatment is associated with craniosynostosis in infants, may adversely affect the tempo of brain maturation, and may accelerate the bone age and result in premature epiphyseal closure and compromised adult stature [see Dosage and Administration (2.6) and Adverse Reactions (6)].
Acquired Hypothyroidism in Pediatric Patients
Closely monitor patients to avoid undertreatment and overtreatment. Undertreatment may result in poor school performance due to impaired concentration and slowed mentation and in reduced adult height. Overtreatment may accelerate the bone age and result in premature epiphyseal closure and compromised adult stature.
Treated children may manifest a period of catch-up growth, which may be adequate in some cases to normalize adult height. In children with severe or prolonged hypothyroidism, catch-up growth may not be adequate to normalize adult height [see Adverse Reactions (6)].
Because of the increased prevalence of cardiovascular disease among the elderly, initiate liothyronine sodium at less than the full replacement dose [see Dosage and Administration (2.3) and Warnings and Precautions (5.1)]. Atrial arrhythmias can occur in elderly patients. Atrial fibrillation is the most common of the arrhythmias observed with thyroid hormone overtreatment in the elderly.
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