CYTOMEL Tablet Ref.[10799] Active ingredients: Liothyronine

Source: FDA, National Drug Code (US)  Revision Year: 2019 

1. Indications and Usage

1.1 Hypothyroidism

CYTOMEL is indicated as a replacement therapy in primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) congenital or acquired hypothyroidism.

1.2 Pituitary Thyroid-Stimulating Hormone(TSH) Suppression

CYTOMEL is indicated as an adjunct to surgery and radioiodine therapy in the management of well-differentiated thyroid cancer.

1.3 Thyroid Suppression Test

CYTOMEL is indicated as a diagnostic agent in suppression tests to differentiate suspected mild hyperthyroidism or thyroid gland autonomy.

Limitations of Use:

  • CYTOMEL is not indicated for suppression of benign thyroid nodules and nontoxic diffuse goiter in iodine-sufficient patients as there are no clinical benefits and overtreatment with CYTOMEL may induce hyperthyroidism [see Warnings and Precautions (5.4)].
  • CYTOMEL is not indicated for treatment of hypothyroidism during the recovery phase of subacute thyroiditis.

2. Dosage and Administration

2.1 General Principles of Dosing

The dose of CYTOMEL for hypothyroidism or pituitary TSH suppression depends on a variety of factors including: the patient’s age, body weight, cardiovascular status, concomitant medical conditions (including pregnancy), concomitant medications, co-administered food and the specific nature of the condition being treated [see Dosage and Administration (2.2, 2.3, 2.4), Warnings and Precautions (5), and Drug Interactions (7)]. Dosing must be individualized to account for these factors and dose adjustments made based on periodic assessment of the patient’s clinical response and laboratory parameters [see Dosage and Administration (2.4)].

Administer CYTOMEL tablets orally once daily.

2.2 Recommended Dosage for Hypothyroidism

Adults

The recommended starting dosage is 25 mcg orally once daily. Increase the dose by 25 mcg daily every 1 or 2 weeks, if needed. The usual maintenance dose is 25 mcg to 75 mcg once daily.

For elderly patients or patients with underlying cardiac disease, start with CYTOMEL 5 mcg once daily and increase by 5 mcg increments at the recommended intervals.

Serum TSH is not a reliable measure of CYTOMEL dose adequacy in patients with secondary or tertiary hypothyroidism and should not be used to monitor therapy. Use the serum T3 level to monitor adequacy of therapy in this patient population.

Pediatric Patients

The recommended starting dosage is 5 mcg once daily, with a 5 mcg increase every 3 to 4 days until the desired response is achieved. Infants a few months old may require 20 mcg once daily for maintenance. At 1 year of age, 50 mcg once daily may be required. Above 3 years of age, the full adult dosage may be necessary [see Use in Specific Populations (8.4)].

Newborns (0 to 3 months) at Risk for Cardiac Failure:

Consider a lower starting dose in infants at risk for cardiac failure. Increase the dose as needed based on clinical and laboratory response.

Pediatric Patients at Risk for Hyperactivity:

To minimize the risk of hyperactivity in pediatric patients, start at one-fourth the recommended full replacement dose, and increase on a weekly basis by one-fourth the full recommended replacement dose until the full recommended replacement dose is reached.

Pregnancy

Pre-existing Hypothyroidism: Thyroid hormone dose requirements may increase during pregnancy. Measure serum TSH and free-T4 as soon as pregnancy is confirmed and, at minimum, during each trimester of pregnancy. In patients with primary hypothyroidism, maintain serum TSH in the trimester-specific reference range. For patients with serum TSH above the normal trimester-specific range, increase the dose of thyroid hormone and measure TSH every 4 weeks until a stable dose is reached and serum TSH is within the normal trimester-specific range. Reduce thyroid hormone dosage to pre-pregnancy levels immediately after delivery and measure serum TSH levels 4 to 8 weeks postpartum to ensure thyroid hormone dose is appropriate.

2.3 Recommended Dosage for TSH Suppression in Well-Differentiated Thyroid Cancer

The dose of CYTOMEL should target TSH levels within the desired therapeutic range. This may require higher doses, depending on the target level for TSH suppression.

2.4 Recommended Dosage for Thyroid Suppression Test

The recommended dose is 75 mcg to 100 mcg daily for 7 days, with radioactive iodine uptake being determined before and after the 7 day administration of CYTOMEL. If thyroid function is normal, the radioiodine uptake will drop significantly after treatment. A 50% or greater suppression of uptake indicates a normal thyroid-pituitary axis.

2.5 Switching from Levothyroxine to CYTOMEL

CYTOMEL has a rapid onset of action and residual effects of the other thyroid preparation may persist for the first several weeks after initiating CYTOMEL therapy. When switching a patient to CYTOMEL, discontinue levothyroxine therapy and initiate CYTOMEL at a low dosage. Gradually increase the CYTOMEL dose according to the patient’s response.

2.6 Monitoring TSH and Triiodothyronine (T3) Levels

Assess the adequacy of therapy by periodic assessment of laboratory tests and clinical evaluation. Persistent clinical and laboratory evidence of hypothyroidism despite an apparent adequate replacement dose of CYTOMEL may be evidence of inadequate absorption, poor compliance, drug interactions, or a combination of these factors.

Adults

In adult patients with primary hypothyroidism, monitor serum TSH periodically after initiation of the therapy or any change in dose. To check the immediate response to therapy before the TSH has had a chance to respond or if your patient’s status needs to be assessed prior to that point, measurement of total T3 would be most appropriate. In patients on a stable and appropriate replacement dose, evaluate clinical and biochemical response every 6 to 12 months and whenever there is a change in the patient’s clinical status.

Pediatrics

In pediatric patients with hypothyroidism, assess the adequacy of replacement therapy by measuring serum TSH and T3 levels. For pediatric patients three years of age and older, the recommended monitoring is every 3 to 12 months thereafter, following dose stabilization until growth and puberty are completed. Poor compliance or abnormal values may necessitate more frequent monitoring. Perform routine clinical examination, including assessment of development, mental and physical growth, and bone maturation, at regular intervals.

While the general aim of therapy is to normalize the serum TSH level, TSH may not normalize in some patients due to in utero hypothyroidism causing a resetting of pituitary-thyroid feedback. Failure of the serum TSH to decrease below 20 IU per liter after initiation of CYTOMEL therapy may indicate the child is not receiving adequate therapy. Assess compliance, dose of medication administered, and method of administration prior to increasing the dose of CYTOMEL [see Warnings and Precautions (5.1) and Use in Specific Populations (8.4)].

Secondary and Tertiary Hypothyroidism

Monitor serum T3 levels and maintain in the normal range.

10. Overdosage

The signs and symptoms of overdosage are those of hyperthyroidism [see Warnings and Precautions (5.4) and Adverse Reactions (6)]. In addition, confusion and disorientation may occur. Cerebral embolism, seizure, shock, coma, and death have been reported. Symptoms may not necessarily be evident or may not appear until several days after ingestion.

Reduce the CYTOMEL dose or temporarily discontinued if signs or symptoms of overdosage occur. Initiate appropriate supportive treatment as dictated by the patient’s medical status.

For current information on the management of poisoning or overdosage, contact the National Poison Control Center at 1-800-222-1222 or www.poison.org.

16.2. Storage and Handling

Store between 15°C and 30°C (59°F and 86°F).

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