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Synthroid (Levothyroxine Sodium) - Summary



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.

SYNTHROID (LEVOTHYROXINE) is indicated for the following:

WARNINGS and PRECAUTIONS), including thyroid nodules (see WARNINGS and PRECAUTIONS), subacute or chronic lymphocytic thyroiditis (Hashimoto's thyroiditis), multinodular goiter (see WARNINGS and PRECAUTIONS) and, as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer.


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Published Studies Related to Synthroid (Levothyroxine)

The effect of levothyroxine and selenomethionine on lymphocyte and monocyte cytokine release in women with Hashimoto's thyroiditis. [2011.07]
CONTEXT: No previous study determined monocyte- and lymphocyte-suppressing effects of levothyroxine and selenomethionine and assessed whether their coadministration is superior to treatment with only one of these drugs. OBJECTIVE: Our objective was to compare the effect of levothyroxine and selenomethionine on monocyte and lymphocyte cytokine release and systemic inflammation in patients with Hashimoto's thyroiditis... CONCLUSIONS: Despite affecting different types of inflammatory cells, levothyroxine and selenomethionine exhibit a similar systemic antiinflammatory effect in euthyroid females with Hashimoto's thyroiditis. This action, which correlates with a reduction in thyroid peroxidase antibody titers, may be associated with clinical benefits in the prevention and management of Hashimoto's thyroiditis, particularly in subjects receiving both agents.

Pharmacokinetic equivalence of a levothyroxine sodium soft capsule manufactured using the new food and drug administration potency guidelines in healthy volunteers under fasting conditions. [2011.06]
CONCLUSIONS: The levothyroxine soft capsule formulated with the stricter new potency guideline set forward by the Food and Drug Administration met equivalence criteria in terms of rate and extent of exposure under fasting conditions to the reference tablet formulation. Clinical doses of the capsule formulation can be given using any combination of the commercialized strengths.

Effect of levothyroxine treatment on in vitro fertilization and pregnancy outcome in infertile women with subclinical hypothyroidism undergoing in vitro fertilization/intracytoplasmic sperm injection. [2011.04]
OBJECTIVE: To investigate whether levothyroxine (LT4) treatment has beneficial effects on IVF results and pregnancy outcome in infertile patients with subclinical hypothyroidism undergoing IVF/intracytoplasmic sperm injection (ICSI)...

Metabolic effects of liothyronine therapy in hypothyroidism: a randomized, double-blind, crossover trial of liothyronine versus levothyroxine. [2011]
CONCLUSIONS: The substitution of L-T(3) for L-T(4) at equivalent doses (relative

Effects of evening vs morning levothyroxine intake: a randomized double-blind crossover trial. [2010.12.13]
BACKGROUND: Levothyroxine sodium is widely prescribed to treat primary hypothyroidism. There is consensus that levothyroxine should be taken in the morning on an empty stomach. A pilot study showed that levothyroxine intake at bedtime significantly decreased thyrotropin levels and increased free thyroxine and total triiodothyronine levels. To date, no large randomized trial investigating the best time of levothyroxine intake, including quality-of-life evaluation, has been performed... CONCLUSIONS: Levothyroxine taken at bedtime significantly improved thyroid hormone levels. Quality-of-life variables and plasma lipid levels showed no significant changes with bedtime vs morning intake. Clinicians should consider prescribing levothyroxine intake at bedtime. TRIAL REGISTRATION: isrctn.org Identifier: ISRCTN17436693 (NTR959).

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Clinical Trials Related to Synthroid (Levothyroxine)

Combined Levothyroxine/Liothyronine Supplementation in Hypothyroid Patients With Brain Tumors [Terminated]
Primary Objectives: 1. Assess whether combined treatment with Levothyroxine and Liothyronine improves learning and memory. 2. Explore the relationship between T3 treatment and other domains of cognitive function, quality of life, and mood.

Thyroid Hormone Dose Adjustment in Pregnancy [Recruiting]
Our aim is to compare the safety and efficacy of 2 different empiric levothyroxine dose adjustment recommendations to be made at the first confirmation of pregnancy in women with a history of hypothyroidism. Subjects will be women with a prior diagnosis of hypothyroidism who are taking thyroid hormone replacement and who are less than 8 weeks pregnant. Upon confirmation of pregnancy, subjects will be randomized to increase their weekly thyroid hormone dose by either 2 or 3 tablets (28 or 42%). Thyroid function will be evaluated every two weeks in the first 20 weeks and then again at week 30 and post-partum. Primary endpoints will be the proportion of women in each group who remain euthyroid throughout the first trimester and throughout pregnancy.

Evaluation of the Efficacy and Safety of Levothyroxine in Brain Death Organ Donors: a Randomized Controled Trial [Recruiting]

Desiccated Thyroid Extract and Levothyroxine for Hypothyroidism Treatment [Recruiting]
Our hypothesis is that hypothyroid patients on DTE may have a decrease in symptoms, an improvement of cognitive function, and an increase in sense of well-being/ quality of life equivalently compared with L-T4.

Fasting Study of Levothyroxine Sodium Tablets 300 Mcg to Synthroid® Tablets 300 Mcg [Completed]
The objective of this study was to investigate the bioequivalence of Mylan's levothyroxine sodium 300 mcg tablets to Abbott's Synthroid® 300 mcg tablets following a single, oral 600 mcg dose (2 × 300 mcg) administered under fasting conditions.

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Reports of Suspected Synthroid (Levothyroxine) Side Effects

Alopecia (86)Fatigue (83)Headache (57)Drug Ineffective (51)Blood Thyroid Stimulating Hormone Increased (49)Weight Increased (49)Feeling Abnormal (49)Dizziness (47)Palpitations (46)Anxiety (46)more >>


Based on a total of 53 ratings/reviews, Synthroid has an overall score of 7.87. The effectiveness score is 7.81 and the side effect score is 9.09. The scores are on ten point scale: 10 - best, 1 - worst. Below are selected reviews: the highest, the median and the lowest rated.

Synthroid review by 46 year old female patient

Overall rating:  
Effectiveness:   Considerably Effective
Side effects:   No Side Effects
Treatment Info
Condition / reason:   hypothyroid
Dosage & duration:   25 mcg (dosage frequency: 1/day) for the period of for the last 9 mos
Other conditions:   mild hypertension
Other drugs taken:   lexapro, welbutrin, nexium, Benicar
Reported Results
Benefits:   Increased energy; I happened to be without the drug for one week, and felt absolutely terrible - like I was completely knocked down.
Side effects:   no side effects that i can remember.
Comments:   The doctor ran a series of blood/chemical tests - thyroid, testosterone and DHEA levels. All were somewhat low, the synthroid in particular. We've started out with fairly low levels of each.


Synthroid review by 42 year old female patient

Overall rating:  
Effectiveness:   Considerably Effective
Side effects:   Mild Side Effects
Treatment Info
Condition / reason:   hypothyroidism
Dosage & duration:   100mcg (dosage frequency: once daily) for the period of still taking since 10 years on
Other conditions:   none
Other drugs taken:   none
Reported Results
Benefits:   Clearer thinking; improved outlook and energy level.
Side effects:   I have had a persistent cough since taking this drug.
Comments:   Taken first thing with glass of water and no food for 30 minutes. Doctor did not see the connection between cough and Synthroid,(chest Xray came back fine) however as it did bother my stomach briefly at time of dosing, I decided it might be affecting the stomach lining. Recently towards late afternoon or before retiring will take Tagamet or some generic stomach med. I DO NOT experience heartburn, however, this routine seems to reduce the embarrassing cough significantly. This was my own resolution after trying many allergy medicines once or twice which did not stop the cough at all. Was also given sample of Advair which I did not use due to negative side effects I read about on internet before using. I am seeking a more natural and effective solution to replace the Synthroid with something that will treat source of low thyroid as well as the symptoms.


Synthroid review by 63 year old female patient

Overall rating:  
Effectiveness:   Moderately Effective
Side effects:   Severe Side Effects
Treatment Info
Condition / reason:   low thyroid
Dosage & duration:   200 mcg (dosage frequency: 1 time per day) for the period of 10 years
Other conditions:   none
Other drugs taken:   none
Reported Results
Benefits:   The synthroid medication did, for most of the ten years while I took it, keep my thyroid levels where they were supposed to be.
Side effects:   After taking this synthroid medication for a period of about 10 years, here is what happened. We were on vacation in another state and all of a sudden I began to feel extremely horrible-- very weak, with a rapid heart beat. We were getting ready to get on an airplane and come home. So I thought if I can just get to my home town and get to a hospital, they can surely figure out what is wrong with me. We arrived at our home airport and then we went straight to the emergency room, where they ran several tests and I was there for several hours, but they could find nothing wrong with me. So they told me to go to my regular doctor the next day, which I did of course and he ran a blood test and found that it was the thyroid medication that was causing my problems.
Comments:   I was able to find an osteopathic doctor who put me on a natural thyroid, not a synthetic, he calld it a dessicated thyroid which came from an animal source, so I was able to get off the synthetic. Then after being on that for a while, he was able to get me off of that and I took a natural supplement, L- tyrosine It was wonderful to get off of a prescription medication. I hope this information may be helpful to someone out there.

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Page last updated: 2013-02-10

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