Comparisons
Retatrutide vs Phentermine
Direct Answer
Retatrutide and phentermine work through entirely different mechanisms. Phentermine is FDA-approved for short-term use and produces modest weight loss (~3–5% at 12 weeks). Retatrutide is investigational with Phase 3 evidence showing 28.3% mean weight loss at 80 weeks. They are not directly comparable — different mechanisms, durations, and evidence bases.
Comparison
| Category | Retatrutide | Phentermine |
|---|---|---|
| Drug class | Triple GLP-1/GIP/glucagon agonist (incretin-based) | Sympathomimetic amine; norepinephrine-releasing agent |
| FDA status | Investigational — not approved | FDA-approved for short-term obesity treatment (typically ≤12 weeks); Schedule IV controlled substance |
| Mechanism | Reduces appetite via GLP-1/GIP/glucagon receptors; increases energy expenditure | Stimulates norepinephrine release; suppresses appetite via CNS stimulation |
| Efficacy | 28.3% mean weight loss at 80 weeks (Phase 3 TRIUMPH-1 topline, 12 mg) | ~3–5% weight loss at 12 weeks in short-term trials; limited long-term data |
| Duration of use | Studied up to 80+ weeks in Phase 3 | Approved for short-term use only (typically ≤12 weeks); long-term use is off-label |
| Cardiovascular effects | Heart rate increase documented; TRIUMPH-Outcomes trial ongoing | Increases heart rate and blood pressure; not recommended in cardiovascular disease |
| Availability | Not commercially available; Phase 3 trials only | Widely available by prescription; generic available |
Note: Retatrutide is not FDA approved. TRIUMPH-1 topline results are company-reported; peer-reviewed publication is pending. Cross-comparison only — not a head-to-head trial.
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