Thyroid Hormone Replacement Therapy

Some patients with hypothyroidism can be challenging to treat and require special consideration. Use this section to review the cases of Steve, Jennifer, and Diana to see how to effectively manage their hypothyroidism with SYNTHROID (levothyroxine sodium). The “optimal dose” was determined for each patient as that dosage of thyroxine being taken when the thyrotropin-releasing hormone (TRH) response was normal (ie, an increase in TSH of between 4.7 and 25 mIU/L). Do not administer in foods that decrease absorption of SYNTHROID, such as soybean-based infant formula see DRUG INTERACTIONS. Synthroid is prescribed in tablets that range from 25 to 300 mcg in strength and is usually taken once a day with a full glass of water (about 8 ounces) 30 to 60 minutes before breakfast for best adsorption into the body.

Drugs That May Alter Hepatic Metabolism of T4 (Hypothyroidism)

Treat patients with adrenal insufficiency with replacement glucocorticoids prior to initiating treatment with SYNTHROID see CONTRAINDICATIONS. Titrate the dose of SYNTHROID carefully and monitor response to titration to avoid these effects see DOSAGE AND ADMINISTRATION. Consider the potential for food or drug interactions and adjust the administration or dosage of SYNTHROID as needed see DOSAGE AND ADMINISTRATION, DRUG INTERACTIONS and CLINICAL PHARMACOLOGY. Concurrent use of sympathomimetics and SYNTHROID 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.

• Oral levothyroxine sodium is a synthetic T4 hormone that exerts the same physiologic effect as endogenous T4, thereby maintaining normal T4 levels when a deficiency is present.
• The peak therapeutic effect of a given dose of SYNTHROID may not be attained for 4 to 6 weeks.
• SYNTHROID increases the response to oral anticoagulant therapy.
• Eltroxin is used for hashimoto’s disease, hypothyroidism, after thyroid removal, myxedema coma …
• Concurrent use of tyrosine-kinase inhibitors such as imatinib may cause hypothyroidism.

WARNING: NOT FOR TREATMENT OF OBESITY OR FOR WEIGHT LOSS

• Consider the potential for food or drug interactions and adjust the administration or dosage of SYNTHROID as needed see DOSAGE AND ADMINISTRATION, DRUG INTERACTIONS and CLINICAL PHARMACOLOGY.
• Synthroid is a thyroid medicine that replaces a hormone normally produced by your thyroid gland to regulate the body’s energy and metabolism.
• The relative bioavailability of SYNTHROID tablets, compared to an equal nominal dose of oral levothyroxine sodium solution, is approximately 93%.
• In patients on a stable and appropriate replacement dosage, evaluate clinical and biochemical response every 6 to 12 months and whenever there is a change in the patient’s clinical status.
• SYNTHROID may reduce the therapeutic effects of digitalis glycosides.

Children can take the medicine if the tablet is crushed and put into about 1 to 2 teaspoons of water; do not store or delay giving this crushed pill suspension. Doctors often may have to slowly increase the dose; patients should not increase or decrease this medication themselves. Because some preparations of the drug may contain iodine or lactose, patients should tell their doctors about such allergies or reactions to these components.

More Info on this Drug

Assess compliance, dose of medication administered, and method of administration prior to increasing the dose of SYNTHROID see WARNINGS AND PRECAUTIONS and Use In Specific Populations. In adult patients with primary hypothyroidism, monitor serum TSH levels after an interval of 6 to 8 weeks after any change in dosage. In patients on a stable and appropriate replacement dosage, evaluate clinical and biochemical response every 6 to 12 months and whenever there is a change in the patient’s clinical status. The recommended starting daily dosage of SYNTHROID in adults with primary, secondary, or tertiary hypothyroidism is based on age and comorbid cardiac conditions, as described in Table 1. For patients at risk of atrial fibrillation or patients with underlying cardiac disease, start with a lower dosage and titrate the dosage more slowly to avoid exacerbation of cardiac symptoms.

Monitor patients receiving concomitant SYNTHROID and sympathomimetic agents for signs and symptoms of coronary insufficiency. Consider changes in TBG concentration when interpreting T4 and T3 values. Measure and evaluate unbound (free) hormone and/or determine the free-T4 index (FT4I) in this circumstance. Pregnancy, infectious hepatitis, estrogens, estrogen-containing oral contraceptives, and acute intermittent porphyria increase TBG concentration. Nephrosis, severe hypoproteinemia, severe liver disease, acromegaly, androgens, and corticosteroids decrease TBG concentration.

The major pathway of thyroid hormone metabolism is through sequential deiodination. Approximately 80% of circulating T3 is derived from peripheral T4 by monodeiodination. The liver is the major site of degradation for both T4 and T3, with T4 deiodination also occurring at a number of additional sites, including the kidney and other tissues. Approximately 80% of the daily dose of T4 is deiodinated to yield equal amounts of T3 and reverse T3 (rT3).

Seizures occurred in a 3-yearold child ingesting 3.6 mg of levothyroxine. Symptoms may not necessarily be evident or may not appear until several days after ingestion of levothyroxine sodium. Serum TSH levels should be monitored and the SYNTHROID dosage adjusted during pregnancy. Since postpartum TSH levels are similar to preconception values, the SYNTHROID dosage should return to the pre-pregnancy dose immediately after delivery see DOSAGE AND ADMINISTRATION. Consumption of certain foods may affect SYNTHROID absorption thereby necessitating adjustments in dosing see DOSAGE AND ADMINISTRATION. Soybean flour, cottonseed meal, walnuts, and dietary fiber may bind and decrease the absorption of SYNTHROID from the gastrointestinal tract.

SYNTHROID 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 SYNTHROID may induce hyperthyroidism. The Before Breakfast Club is a program designed to help support your patients on SYNTHROID therapy. After joining, patients will receive exclusive benefits including savings, tips, and tools to help your patients make the most of their SYNTHROID treatment.

Adequate levothyroxine treatment during lactation may normalize milk production in hypothyroid lactating mothers with low milk supply. Addition of levothyroxine therapy in patients with diabetes mellitus may worsen glycemic control and result in increased antidiabetic agent or insulin requirements. Carefully monitor glycemic control after starting, changing, or discontinuing SYNTHROID see DRUG INTERACTIONS.

Thyroid hormones, including SYNTHROID, 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 synthroid 33 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. 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.