What is Synthroid®?
Synthroid® is a synthetic form of the thyroid hormone, thyroxine. The primary function of this hormone is to regulate the metabolic rate of the cells found in virtually every tissue in the human body. This hormone is also responsible for regulating body temperature and plays a role in cognitive functioning and in the digestion of food. For people with low thyroid hormone levels, these processes become impaired, leading to a condition known as hypothyroidism, or low thyroid. Synthroid® has been a standard hypothyroidism treatment since the mid-1950s.
The generic name for Synthroid® is levothyroxine sodium, but it is also sold under the brand names Levoxyl®, Levothroid®, and Unithroid®. Most forms of levothyroxine are available in tablet form. However, this medication is sometimes prescribed in powdered form to be mixed with liquid and delivered by intravenous injection. Since there may be differences in concentration of levothyroxine sodium between generic and brands, the dosage may need to be adjusted to achieve effectiveness or to avoid toxicity. In addition, Synthroid® is manufactured in a dozen different strengths.
In addition to treating hypothyroidism, Synthroid® is sometimes used to control an overactive thyroid, or hyperthyroidism. This condition may lead to thyrotoxicosis, or elevated levels of thyroxine being circulated. Since Synthroid® can suppress thyroid hormone release in the right therapeutic dose, it is useful to inhibit the growth of thyroid nodules and goiters. Synthroid® therapy is also sometimes combined with anti-thyroid medications, such as methimazole.
Once treatment with Synthroid® begins, it may take several weeks to see the desired results. However, if symptoms do not improve within that time, patients are advised to consult with their health care professional to determine if the dosage needs to be adjusted. In addition, patients taking Synthroid® should have their thyroxine levels checked periodically through a Thyroid-Stimulating Hormone (TSH) test. Unless conditions indicate otherwise, this test is usually administered twice a year.
Most people who begin Synthroid® therapy can expect to stay on this medication for the rest of their lives. However, adjustments to the medication may be needed periodically since life changes can affect its efficacy. For instance, pregnancy and menopause are two factors that can impact thyroid metabolism. In addition, complications may arise as thyroid levels are normalized if other conditions are present. For instance, those with heart conditions taking beta-blocking drugs or insulin for diabetes may need to have the dosages of these medications adjusted while taking Synthroid®.
While Synthroid® is generally well tolerated in most people, there are side effects associated with this medication. Common symptoms include profuse sweating, rapid heart rate or pulse, headache, fever, insomnia, nausea, and unexpected weight loss. In addition, some women may experience irregular menstrual cycles.
Synthroid® may also interact with other medications. For instance, it is known that this drug can increase the action of warfarin (Coumadin) and other blood-thinners. In addition, patients taking Synthroid® that are also being treated with epinephrine for coronary artery disease may have an increased risk of suffering a heart attack.
Written by Karyn Maier
