Synthroid (Levothyroxine Sodium) - Summary

SYNTHROID 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.

Levothyroxine sodium is used for the following indications:

Hypothyroidism --As replacement or supplemental therapy in congenital or acquired hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis. Specific indications include: primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) hypothyroidism and subclinical hypothyroidism. Primary hypothyroidism may result from functional deficiency, primary atrophy, partial or total congenital absence of the thyroid gland, or from the effects of surgery, radiation, or drugs, with or without the presence of goiter.

Pituitary TSH Suppression --In the treatment or prevention of various types of euthyroid goiters (see 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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NEWS HIGHLIGHTS

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)

Fasting Study of Levothyroxine Sodium Tablets 200 mg to Synthroid Tablets 200 mg [Completed]
The objective of this study was to investigate the bioequivalence of Mylan's levothyroxine sodium 200 μg tablets to Abbott's Synthroid® 200 μg tablets following a single 600 μg (3 x 200 μg) dose administration in healthy volunteers under fasting conditions. Twenty-nine healthy, non-smoking, subjects between the ages of 18 and 47 completed this open-label, randomized, two-period, two-treatment, single-dose crossover study conducted by Dr. James D. Carlson at PRACS Institute, Ltd., Fargo, ND. Statistical analysis of the data revealed that 90% confidence intervals were within the acceptable bioequivalent range of 80% and 125% for the natural log transformed parameters LNAUC0-48hr and LNCPEAK for baseline corrected total L-thyroxine. This study demonstrated that Mylan's 200 μg levothyroxine sodium tablets are bioequivalent to Abbott's Synthroid® 200 μg tablets following a single, oral 600 μg (3 x 200 μg) dose under fasting conditions

Fasting Study of Levothyroxine Sodium Tablets 300 μg to Synthroid® Tablets 300 μg [Completed]
The objective of this study was to investigate the bioequivalence of Mylan's levothyroxine sodium 300 μg tablets to Abbott's Synthroid® 300 μg tablets following a single 600 μg (2 x 300 μg) dose administered in healthy volunteers under fasting conditions. Single-dose pharmacokinetic parameters for baseline corrected total L-thyroxine and non-baseline corrected total L-triiodothyronine were calculated using noncompartmental techniques.

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.

Generic vs. Name-Brand Levothyroxine [Recruiting]
This study compares two different brands of thyroxine (thyroid hormone). Currently, pharmacists may be substituting generic formulations of thyroid hormone without your doctor knowing about this. Although a small difference in thyroid function is not significant in most healthy children, adolescents and adults, in infants and toddlers even a small difference in thyroid function can have important harmful consequences on brain development. The purpose of the present study is to learn whether the difference between brands of thyroid hormone that are currently being substituted is sufficient to cause a difference in thyroid function.

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.

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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 >>

PATIENT REVIEWS / RATINGS / COMMENTS

Synthroid review by 46 year old female patient
		Rating
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
		Rating
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
		Rating
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.