Q and A: Thyroxine Preparations American Thyroid Association

The majority of the SYNTHROID dose is absorbed from the jejunum and upper ileum. 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. Some studies suggest that generic levothyroxine, the synthetic form of the thyroid hormone thyroxine (T4), is non-inferior to Synthroid in treating mild hypothyroidism.

This list is not complete and many other drugs may interact with levothyroxine. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Generic drugs help reduce treatment costs while generally delivering equal (non-inferior) results. However, there is debate as to whether generic levothyroxine is equally effective as the brand name version, Synthroid, in treating hypothyroidism. The higher affinity of both TBG and TBPA for T4 partially explains the higher serum levels, slower metabolic clearance, and longer half-life of T4 compared to T3. Protein-bound thyroid hormones exist in reverse equilibrium with small amounts of free hormone.

Is levothyroxine sodium safe to take if I’m pregnant or breastfeeding?

Others have found that switching from Synthroid to a generic may make it harder to maintain tight control of your thyroid hormone levels. This means that ingestion of 1 mg of generic levothyroxine may not have the same effect on the body as 1 mg of another generic or branded levothyroxine. Practically speaking, this means that thuoc synthroid when changing between levothyroxine manufactured by different pharmaceutical companies, a change in dose may be necessary to maintain the desired effect or to prevent toxicity. When switching between brands or generics, it is important to ensure that both preparations are equivalent or to check blood thyroid levels weekly. In adult patients with primary hypothyroidism, monitor serum TSH levels after an interval of 6 to 8 weeks after any change in dosage.

Side Effects for Synthroid

• The study’s authors looked at hypothyroidism patients between January 2008 and March 2016 who were started on either Synthroid or generic levothyroxine within a year of being diagnosed.
• The higher affinity of both TBG and TBPA for T4 partially explains the higher serum levels, slower metabolic clearance, and longer half-life of T4 compared to T3.
• 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.
• All problems (adverse events) related to a medicine or medical device used for treatment or in a procedure should be reported to the Medicines and Healthcare products Regulatory Agency using the Yellow Card Scheme.
• Because some preparations of the drug may contain iodine or lactose, patients should tell their doctors about such allergies or reactions to these components.

In children, having enough thyroid hormone is important for normal mental and physical development. Myxedema coma is a life-threatening emergency characterized by poor circulation and hypometabolism and may result in unpredictable absorption of levothyroxine sodium from the gastrointestinal tract. Use of oral thyroid hormone drug products is not recommended to treat myxedema coma. Administer thyroid hormone products formulated for intravenous administration to treat myxedema coma. Hypersensitivity reactions to inactive ingredients have occurred in patients treated with thyroid hormone products.

What are the side effects of levothyroxine sodium?

• Levothroid is used for hashimoto’s disease, hypothyroidism, after thyroid removal, myxedema coma …
• Long-term therapy decreases bone mineral density; use lowest dose in postmenopausal women and women using suppressive doses.
• A portion of the conjugated hormone reaches the colon unchanged and is eliminated in the feces.
• The peak therapeutic effect of a given dose of SYNTHROID may not be attained for 4 to 6 weeks.
• You would then want to make sure that you check your thyroid lab tests after about 6 weeks to ensure that you did well with the transition.
• And you have to be your own best advocate, working alongside a healthcare provider who will listen to you and guide you to the right solution.

Notify your doctor if you experience serious side effects of Synthroid including rapid heartbeat, fluttering in your chest, or chest pain. Get medical help right away, if you have any of the symptoms listed above. In this case, you may find relief in simply switching from the name brand to generic or vice versa. There is a potential difference between Levothyroxine and Synthroid but the difference is probably not noticeable for most people.

In addition, because T3 is more potent than T4, patients who use T3 tend to have more side effects. Liothyronine, on the other hand, contains the most potent thyroid hormone which is known as T3 or triiodothyronine. In some situations, you may find that switching from Synthroid to Levothyroxine (or vice versa) still doesn’t help remove all of your symptoms. Even though Tirosint is more expensive than other medications there are some coupon options that you can use to help reduce the cost.

• Even though Synthroid and Levothyroxine contain the same active ingredient, they may not be tolerated equally among all patients.
• Levothyroxine (Synthroid, Levoxyl, Levothroid, Unithroid, Tirosint, Levo-T) is a synthetic version of the principle thyroid hormone, thyroxine (T4), which is made and released by the thyroid gland.
• It’s important to remember that the cost of medications often depends on which pharmacy you go to.
• This list is not complete and many other drugs may interact with levothyroxine.

You should not use levothyroxine if you are allergic to glycerin or edetate disodium, or if you have an untreated or uncontrolled adrenal gland disorder. While the drug has been around since 1955, it was only formally approved by the FDA as a « new drug » in 2002. Thereafter, the first generic was awarded FDA approval only two years later, in 2004. Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Synthroid only for the indication prescribed.

Most medications are availablein brand-name and generic preparations. Brand-name preparations are usually the first ones available on the market. After a period of time, other manufacturers are allowed to make generic versions of the same drug. This article explains how the potency can vary between brand-name and generic versions of levothyroxine. It also explains the possible consequences of switching, as well as when a brand-name product is the best choice.

Adult Thyroid Information

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. Familial hyper- or hypo-thyroxine binding globulinemias have been described, with the incidence of TBG deficiency approximating 1 in 9000.

All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. 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. 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.