Weight-Based Levothyroxine Dosage Adjustment for Hypothyroidism
Weight-Based Levothyroxine Dosage Adjustment for Hypothyroidism
Levothyroxine is used in adults and children to treat hypothyroidism (underactive thyroid – a condition where the thyroid gland does not produce enough thyroid hormone). Synthroid should not be used to treat obesity or weight problems. Dangerous side effects or death can occur from the misuse of levothyroxine, especially if you are taking any other weight-loss medications or appetite suppressants. Synthroid is also used in patients who need surgery and radioiodine therapy to manage a type of thyroid cancer called well-differentiated thyroid cancer. 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).
1 Important Administration Instructions
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 (2.3). Addition of SYNTHROID therapy in patients with diabetes mellitus may worsen glycemic control and result in increased antidiabetic agent or insulin requirements.
Levothyroxine (T4) and liothyronine (T3) may be administered via a nasogastric tube but the preferred route of administration of both hormones is intravenous. Levothyroxine sodium (T4) is given at a starting dose of 400 mcg (100 mcg/mL) given rapidly, and is usually well tolerated, even in the elderly. This initial dose is followed by daily supplements of 100 to 200 mcg given IV. Normal T4 levels are achieved in 24 hours followed in 3 days by threefold elevation of T3.
The relative bioavailability of SYNTHROID tablets, compared to an equal nominal dose of oral levothyroxine sodium solution, is approximately 93%. T4 absorption is increased by fasting, and decreased in malabsorption syndromes and by certain foods such as soybeans. In addition, many drugs and foods affect T4 absorption see Drug Interactions (7).
- Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use levothyroxine only for the indication prescribed.
- As noted in the article, it is important to regularly monitor the TSH level until it is in the normal range, then make future adjustments based on symptoms or periodic testing.
- Generally, thyroid replacement treatment is to be taken for life.
- Absorption of orally administered T4 from the gastrointestinal tract ranges from 40% to 80%.
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Having low thyroid synthroid forms hormone levels during pregnancy could harm both mother and baby. Since thyroid hormone occurs naturally in the body, almost anyone can take levothyroxine. However, you may not be able to take this medicine if you have certain medical conditions. Biotin supplementation may interfere with immunoassays for TSH, T4, and T3, resulting in erroneous thyroid hormone test results.
- This initial dose is followed by daily supplements of 100 to 200 mcg given IV.
- Serum TSH levels should be monitored and the SYNTHROID dosage adjusted during pregnancy.
- Carefully monitor glycemic control, especially when thyroid therapy is started, changed, or discontinued see Warnings and Precautions (5.5).
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- Those starting on Zepbound will take Zepbound 2.5 mg for four weeks before increasing their dosage to 5 mg.
- Enter medications to view a detailed interaction report using our Drug Interaction Checker.
- Initiate SYNTHROID therapy in this population at lower doses than those recommended in younger individuals or in patients without cardiac disease see Dosage and Administration (2.3) and Use in Specific Populations (8.5).
- This is not a complete list of side effects and others may occur.
These include urticaria, pruritus, skin rash, flushing, angioedema, various gastrointestinal symptoms (abdominal pain, nausea, vomiting and diarrhea), fever, arthralgia, serum sickness, and wheezing. Hypersensitivity to levothyroxine itself is not known to occur. For adult patients with primary hypothyroidism, titrate until the patient is clinically euthyroid and the serum TSH returns to normal see Dosage and Administration (2.3). SYNTHROID is indicated in adult and pediatric patients, including neonates, as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer. For pregnant patients with pre-existing hypothyroidism, measure serum TSH and free-T4 as soon as pregnancy is confirmed and, at minimum, during each trimester of pregnancy.
Acute adrenal crisis in patients with concomitant adrenal insufficiency
The SYNTHROID dosage is based on the target level of TSH suppression for the stage and clinical status of thyroid cancer. The recommended daily dosage of SYNTHROID in pregnant patients is described in Table 3. Pediatric dosage should follow the recommendations summarized in Table 1. In infants with congenital hypothyroidism, therapy with full doses should be instituted as soon as the diagnosis has been made. Thyroid hormones should be administered cautiously to patients in whom there is strong suspicion of thyroid gland autonomy, in view of the fact that the exogenous hormone effects will be additive to the endogenous source. With an FDA-approved medicine like Wegovy®, healthcare professionals and patients can have clarity and confidence in knowing the medicine they are using has undergone rigorous review for safety, effectiveness, and quality.
Soybean flour, cottonseed meal, walnuts, and dietary fiber may bind and decrease the absorption of SYNTHROID from the gastrointestinal tract. Grapefruit juice may delay the absorption of levothyroxine and reduce its bioavailability. Evaluate the need for dosage adjustments when regularly administering within one hour of certain foods that may affect SYNTHROID absorption see Dosage and Administration (2.2 and 2.3), Drug Interactions (7.9), and Clinical Pharmacology (12.3).
SYNTHROID 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 SYNTHROID dose is increased. Closely monitor coagulation tests to permit appropriate and timely dosage adjustments. Hypersensitivity reactions to inactive ingredients have occurred in patients treated with thyroid hormone products.