Synthroid (Levothyroxine Sodium) Drug Information: Description, User Reviews, Drug Side Effects, Interactions

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May 26, 2012

Synthroid

Hashimoto's Thyroiditis »

Introduction to Hashimoto's thyroiditis

Hashimoto's thyroiditis is the most common cause of hypothyroidism in the United States. It is named after the first doctor who described this condition, Dr. Hakaru Hashimoto, in 1912.

What causes Hashimoto's thyroiditis?

Hashimoto's thyroiditis is a condition caused by inflammation of the thyroid gland. It is an autoimmune disease, which means that the body inappropriately attacks the thyroid gland--as if it was foreign tissue. The underlying cause of the autoimmune process still is unknown. Hashimoto's thyroiditis tends to occur in families, and is associated with a clustering of other autoimmune conditions such as Type 1 diabetes, and celiac disease. Hashimoto's thyroiditis is 5-10 times more common in women than in men and most often starts in adulthood. Blood drawn from patients with Hashimoto's throiditis reveals an increased number of antibodies to the enzyme, thyroid pero...

Read the Hashimoto's Thyroiditis article »

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Synthroid

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Synthroid®
(levothyroxine sodium) Tablets, USP

DRUG DESCRIPTION

SYNTHROID® (levothyroxine sodium tablets, USP) contain synthetic crystalline L-3,3',5,5'-tetraiodothyronine sodium salt [levothyroxine (T₄) sodium]. Synthetic T₄ is identical to that produced in the human thyroid gland. Levothyroxine (T₄) sodium has an empirical formula of C₁₅H₁₀I₄N NaO₄ • H₂O, molecular weight of 798.86 g/mol (anhydrous), and structural formula as shown:

SYNTHROID® (levothyroxine sodium) Structural Formula Illustration

Inactive Ingredients: acacia, confectioner's sugar (contains corn starch), lactose monohydrate, magnesium stearate, povidone, and talc. The following are the color additives by tablet strength:

Strength (mcg)	Color additive(s)
25	FD&C Yellow No. 6 Aluminum Lake
50	None
75	FD&C Red No. 40 Aluminum Lake, FD&C Blue No. 2 Aluminum Lake
88	FD&C Blue No. 1 Aluminum Lake, FD&C Yellow No. 6 Aluminum Lake, D&C Yellow No. 10 Aluminum Lake
100	D&C Yellow No. 10 Aluminum Lake, FD&C Yellow No. 6 Aluminum Lake
112	D&C Red No. 27 & 30 Aluminum Lake
125	FD&C Yellow No. 6 Aluminum Lake, FD&C Red No. 40 Aluminum Lake,
	FD&C Blue No. 1 Aluminum Lake
137	FD&C Blue No. 1 Aluminum Lake
150	FD&C Blue No. 2 Aluminum Lake
175	FD&C Blue No. 1 Aluminum Lake, D&C Red No. 27 & 30 Aluminum Lake
200	FD&C Red No. 40 Aluminum Lake
300	D&C Yellow No. 10 Aluminum Lake, FD&C Yellow No. 6 Aluminum Lake, FD&C Blue No. 1 Aluminum Lake

Meets USP Dissolution Test 3

What are the possible side effects of levothyroxine (Levothroid, Levoxyl, Synthroid, Unithroid)?

Stop using levothyroxine and get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have any of these serious side effects:

headache;
sleep problems (insomnia);
nervous or irritable feeling;
fever, hot flashes, sweating;
changes in your menstrual periods;
appetite changes, weight...

Read All Potential Side Effects and See Pictures of Synthroid »

What are the precautions when taking levothyroxine sodium (Synthroid)?

Before taking levothyroxine, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: increased thyroid hormones (thyrotoxicosis), decreased adrenal gland function, heart disease (such as coronary artery disease, irregular heartbeat), high blood pressure, diabetes.

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Current information shows that this drug may be used during pregnancy....

Read All Potential Precautions of Synthroid »

Last reviewed on RxList: 11/1/2010
This monograph has been modified to include the generic and brand name in many instances.