CYTOMEL (liothyronine sodium)
CYTOMEL is indicated for the treatment of Hypothyroidism; Thyroid Cancer; Hyperthyroidism.
How CYTOMEL Works
Liothyronine (T3) exerts its physiologic effects by diffusing into the cell nucleus and binding to thyroid receptor proteins attached to DNA. This hormone-nuclear receptor complex activates gene transcription and the subsequent synthesis of messenger RNA and cytoplasmic proteins. As the active form of thyroid hormone, T3 is the primary mediator of thyroid hormone activity; approximately 80% of circulating T3 is normally derived from the peripheral deiodination of T4.
Development Insights
Details
- Status
- Prescription
- First Approved
- 1956-05-08
- Routes
- ORAL
- Dosage Forms
- TABLET
CYTOMEL Approval History
What CYTOMEL Treats
3 indicationsCYTOMEL is approved for 3 conditions since its original approval in 1956. These indications span multiple therapeutic areas including oncology, immunology, and more.
- Hypothyroidism
- Thyroid Cancer
- Hyperthyroidism
CYTOMEL Boxed Warning
NOT FOR TREATMENT OF OBESITY OR FOR WEIGHT LOSS • Thyroid hormones, including CYTOMEL, 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 the...
WARNING: NOT FOR TREATMENT OF OBESITY OR FOR WEIGHT LOSS • Thyroid hormones, including CYTOMEL, 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 CYTOMEL, 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 , 7.7 , 10 ).
CYTOMEL 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.
Drugs Similar to CYTOMEL
3 of 16FDA-approved drugs for similar conditions. Compare mechanisms and indications to understand treatment alternatives.
Clinical Trial Registry
3 trials| Trial | Sponsor ID | Phase | Status | Title |
|---|---|---|---|---|
| NCT00788307 | MC0252 P30CA015083, MC0252 | Ph 1 | terminated | Gene Therapy and Radioactive Iodine in Treating Patients With Locally Recurrent Prostate Cancer That Did Not Respond to External-Beam Radiation Therapy |
| NCT02760056 MST3K results posted | IRB 15101 | Ph 1 | completed | Thyroid Hormone for Remyelination in Multiple Sclerosis (MS): A Safety and Dose Finding Study |
| NCT01182285 results posted | 100041 10-C-0041 | Ph 2 | completed | A Phase II Trial of Valproic Acid in Patients With Advanced Thyroid Cancers of Follicular Cell Origin |
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.
CYTOMEL FDA Label Details
Indications & Usage
FDA Label (PDF)CYTOMEL is indicated for the treatment of Hypothyroidism; Thyroid Cancer; Hyperthyroidism.
WARNING: NOT FOR TREATMENT OF OBESITY OR FOR WEIGHT LOSS • Thyroid hormones, including CYTOMEL, 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 ineffe...
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Data Sources
Data sourced from official FDA and NIH databases. Click links to verify on original sources.
How We Calculate These Metrics
Trial Activity Stage
Measures the current development activity pattern based on trial phases, status, and trends. Important: This measures R&D activity, not commercial lifecycle.
Trial statuses: "Active" means recruiting or ongoing. "Completed" means reached planned endpoint. "Terminated" means stopped early—often due to safety, efficacy, or business reasons.
- Growth: High proportion of early-phase trials (Phase 1/2), active development
- Expansion: Significant Phase 3 activity, approaching or pursuing approvals
- Mature: Substantial Phase 4 post-marketing studies
- Stable: Mixed phase distribution, steady development
- Declining: Low active trial ratio, reduced R&D investment