Levothroid Generic

Levothyroxine is a synthetic man-made version of the principle thyroid hormone thyroxine T4 that is made and released by the thyroid gland. Thyroid hormone increases the metabolic rate of cells of all tissues in the body. In the fetus and newborn thyroid hormone is important for the growth and development of all tissues including bones and the brain. In adults thyroid hormone helps to maintain brain function food metabolism and body temperature among other effects.

Levothyroxine is usually started at 0.05 mg/day. Starting doses and dose changes may differ with individual patients based upon the presence of cardiovascular disease the development of tolerance reduced effectiveness with continued use side effects to the medication and blood levels of thyroid hormone. It may take one to three weeks after initiating therapy with levothyroxine or changing the dose before effects are seen.

Levothyroxine therapy is usually well-tolerated. If symptoms occur often they are due to toxic levels of thyroid hormone and the symptoms are those of hyperthyroidism. Symptoms may include all or some of the following: chest pain increased heart rate or pulse rate excessive sweating heat intolerance nervousness headache insomnia diarrhea vomiting weight loss or fever. Women may experience irregular menstrual cycles.

Initiation or discontinuation of therapy with levothyroxine in diabetic patients may create a need for an increase or decrease in the required dose of insulin and/or antidiabetic drug e.g. glyburide Micronase.

Levothyroxine may increase the effect of blood thinners such as warfarin Coumadin. Therefore monitoring of blood clotting is necessary and a decrease in the dose of warfarin may be necessary.

Intravenous administration of epinephrine to patients with coronary artery disease may lead to complications ranging from difficulty in breathing to a heart attack. These complications may occur more frequently among patients also taking levothyroxine. Therefore careful observation is needed when intravenous epinephrine is given to patients receiving levothyroxine who also have coronary artery disease.

Converting a state of hypothyroidism underactivity to a normal state euthyroid state with levothyroxine may decrease the actions of certain beta-blocking drugs e.g. metoprolol Lopressor or propranolol Inderal. It may be necessary therefore to change the dose of beta-blocker. For the same reason the dose of digoxin Lanoxin a drug used to manage heart failure or an irregular heart rhythm e.g. atrial-fibrillation also may need to be changed.

Converting hypothyroidism to the euthyroid state with levothyroxine may increase the blood level of theophylline Slo-Bid and it may be necessary to change the dose of theophylline.

Taking levothyroxine at the same time as cholestyramine Questran or colestipol Colestid two cholesterol-lowering drugs may decrease the effect of levothyroxine and lead to hypothyroidism. This occurs because the levothyroxine binds to the cholesterol-lowering drugs and is not absorbed. Taking the levothyroxine one hour before or four hours after cholestyramine or colestipol is necessary to prevent the binding.

Levothyroxine is approved to treat hypothyroidism and to suppress thyroid hormone release in the management of cancerous thyroid nodules and growth of goiters. In addition Synthroid Levoxyl and Levothroid also are prescribed with anti-thyroid drugs for example methimazole Tapazole to manage thyrotoxicosis high thyroid hormone levels due to over-activity of the thyroid gland. Thyrotoxicosis may result in the growth of goiters and/or hypothyroidism.

Levothyroxine tablets usually are kept at room temperature 15-30°C 59-86°F in a light-resistant tight container. However some manufacturers vary in their storage recommendations. Therefore storage conditions for each product should be clarified with a pharmacist.

Powdered levothyroxine for intravenous injection should be used immediately once mixed with a liquid.