SYNTHROID (levothyroxine sodium)
Synthroid is a thyroid hormone replacement indicated for adult and pediatric patients, including neonates, for the treatment of primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) congenital or acquired hypothyroidism. It is also indicated as an adjunct to surgery and radioiodine therapy for the suppression of pituitary thyrotropin (TSH) in the management of thyrotropin-dependent well-differentiated thyroid cancer. Limitations of use: Synthroid is not indicated for the suppression of benign thyroid nodules or nontoxic diffuse goiter in iodine-sufficient patients, nor for the treatment of hypothyroidism during the recovery phase of subacute thyroiditis.
How SYNTHROID Works
Levothyroxine (T4) exerts its physiological actions by diffusing into cell nuclei and binding to thyroid receptor proteins attached to DNA. This hormone-nuclear receptor complex activates gene transcription and the synthesis of messenger RNA and cytoplasmic proteins. Although Synthroid provides exogenous T4, the drug's physiological effects are predominantly mediated by T3, approximately 80% of which is derived from T4 via deiodination in peripheral tissues.
Details
- Status
- Prescription
- First Approved
- 2002-07-24
- Routes
- ORAL
- Dosage Forms
- TABLET
SYNTHROID Approval History
What SYNTHROID Treats
2 indicationsSYNTHROID is approved for 2 conditions since its original approval in 2002. These indications span multiple therapeutic areas including oncology, immunology, and more.
- Hypothyroidism
- Thyroid Cancer
SYNTHROID Boxed Warning
NOT FOR TREATMENT OF OBESITY OR FOR WEIGHT LOSS Thyroid hormones, including SYNTHROID, either alone or with other therapeutic agents, should not be used for the treatment of obesity or for weight loss. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life - threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their...
WARNING: NOT FOR TREATMENT OF OBESITY OR FOR WEIGHT LOSS Thyroid hormones, including SYNTHROID, either alone or with other therapeutic agents, should not be used for the treatment of obesity or for weight loss. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life - threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects [see Adverse Reactions ( 6 ), Drug Interactions ( 7.7 ), and Overdosage ( 10 )] . WARNING: NOT FOR TREATMENT OF OBESITY OR FOR WEIGHT LOSS See full prescribing information for complete boxed warning . Thyroid hormones, including SYNTHROID , should not be used for the treatment of obesity or for weight loss. Doses beyond the range of daily hormonal requirements may produce serious or even life - threatening manifestations of toxicity ( 6 , 10 ).
SYNTHROID Competitive Set
ProThree rings of competition based on shared molecular targets and treated indications.
Direct competitors
Same target(s) AND same indication — head-to-head.
Indication competitors
Same indication, different mechanism — what else might this patient receive?
Filters applied: drops same-active-ingredient (505(b)(2) reformulations), route-mismatch (topical vs systemic), and cross-therapeutic-area matches in same-indication rings.
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Clinical Trial Registry
7 trials| Trial | Sponsor ID | Phase | Status | Title |
|---|---|---|---|---|
| NCT06073665 DOT4 | 1R01AG081698-01, #853300 R01AG081698 | Ph 4 | recruiting | Dosing of LT4 in Older Individuals |
| NCT05526144 | ENDA-010-21F I01CX002436 | Ph 2 | recruiting | Thyroid Hormone for Treatment of Nonalcoholic Steatohepatitis in Veterans |
| NCT05228184 | 20US-T414 | Ph 4 | terminated | Use of Tirosint®-SOL or Tablet Formulations of Levothyroxine in Pediatric Patients With Congenital Hypothyroidism (CH) |
| NCT05823012 results posted | XP-8121-120 | Ph 2 | completed | Study of XP-8121 For the Treatment of Adult Subjects With Hypothyroidism |
| NCT04878614 | IRB#20-002097 | Ph 4 | terminated | Comparison of Levothyroxine Formulation in Hypothyroid Patients With Enteral Feeding |
| NCT03281083 | MRN-01-NAFLD-01 | Ph 2 | terminated | Levothyroxine for Non-Alcoholic Fatty Liver Disease (NAFLD) |
| NCT00921050 | EN_LC_P136 | Ph 2, Ph 3 | completed | Subclinical Hypothyroidism and Mind in the Elderly |
Active Pipeline
Ongoing clinical trials by development phase
Key Completed Trials
Completed studies with published results, ranked by significance
Trial Timeline
Full development history with FDA approval milestones
Understanding FDA Approval Types
| Count | Type | What it means |
|---|---|---|
| - | ORIG | Original approval - drug first enters market |
| - | SUPPL - Efficacy | New indication (new disease/condition approved) |
| - | SUPPL - Labeling | Label text changes (warnings, dosing updates) |
| - | SUPPL - Manufacturing | Production changes (new facility) |
| - | SUPPL - Chemistry | Formulation changes (new dosage strength) |
Green lines in the timeline show ORIG and Efficacy approvals - the clinically meaningful milestones.
SYNTHROID FDA Label Details
Indications & Usage
FDA Label (PDF)SYNTHROID is indicated for the treatment of Hypothyroidism; Thyroid Cancer.
WARNING: NOT FOR TREATMENT OF OBESITY OR FOR WEIGHT LOSS Thyroid hormones, including SYNTHROID, either alone or with other therapeutic agents, should not be used for the treatment of obesity or for weight loss. In euthyroid patients, doses within the range of daily hormonal requirements are ineffect...
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Data Sources
Data sourced from official FDA and NIH databases. Click links to verify on original sources.