Randomised controlled trials
In the trials below, people were assigned at random to take Phentermine / Topiramate ER or a dummy pill (placebo). All the weight loss figures are averages: how much body weight fell from the start.
| Trial | Key result | Source |
|---|---|---|
| [1]CONQUER | 9.8% weight loss at 15/92 mg (full dose) vs. 1.2% placebo. 70% achieved ≥5% loss. Significant blood pressure, triglyceride, and glucose improvements. | The Lancet 2011 ↗ |
| [2]SEQUEL (2-year extension of CONQUER) | Sustained weight loss with continued metabolic improvements at 2 years, confirming durability of effect. | American Journal of Clinical Nutrition 2012 ↗ |
Reported side effects
The rates below come from the CONQUER trial. View source
| Side effect | Frequency in trial |
|---|---|
| Paraesthesia (tingling in hands/feet) | 20% |
| Dry mouth | 21% |
| Constipation | 17% |
| Insomnia | 10% |
| Dizziness | 9% |
| Cognitive effects ('brain fog') | 8% |
Body composition data
No large published body composition substudy is available for phentermine/topiramate specifically. It works mainly by curbing appetite, without the metabolic effects of the GLP-1 drugs. So how much lean mass you keep depends heavily on protein intake and resistance training while you are eating less.
Heart and metabolic data
In CONQUER, there were significant reductions in blood pressure, waist circumference, triglycerides and blood glucose. But phentermine raises heart rate. Careful monitoring is required in people with cardiovascular disease.