From the Guidelines
No, there are no studies directly showing that phentermine is more effective than Ozempic (semaglutide) for weight loss. In fact, current evidence suggests the opposite, with Ozempic and similar GLP-1 receptor agonists like Wegovy (higher-dose semaglutide) typically producing greater weight loss than phentermine 1. Some key points to consider when comparing these medications include:
- Mechanism of action: Phentermine works as an appetite suppressant by affecting neurotransmitters in the brain, while semaglutide works through multiple mechanisms including slowing gastric emptying, increasing satiety signals, and reducing hunger hormones.
- Efficacy: Clinical trials show that semaglutide can help patients lose approximately 15-20% of their body weight over 68 weeks, while phentermine typically produces more modest results of about 3-7% weight loss, with 46% of subjects in the phentermine group achieving 5% weight loss and 20.8% achieving 10% weight loss in a 28-week trial 1.
- Approval and usage: Phentermine is approved only for short-term use (up to 12 weeks) due to concerns about tolerance and side effects, whereas semaglutide can be used long-term.
- Side effects and considerations: The most common side effects of phentermine include dry mouth, difficulty sleeping, dizziness, and irritability, and it should not be used with monoamine oxidase inhibitors or other sympathomimetic amines 1. The choice between medications should be based on individual factors including health status, weight loss goals, cost considerations, and potential side effects, with guidance from a healthcare provider.
From the Research
Comparison of Phentermine and Ozempic for Weight Loss
- There are no direct studies comparing the effectiveness of Phentermine and Ozempic (semaglutide) for weight loss in the provided evidence.
- However, study 2 compares the effectiveness of various weight loss medications, including phentermine-topiramate and semaglutide.
- According to study 2, semaglutide was associated with 11.4% greater weight loss compared to placebo, while phentermine-topiramate was associated with 8.0% greater weight loss.
- Study 3 reports that phentermine/topiramate ER can produce and sustain approximately 10% loss of body weight.
- Study 4 found that phentermine/topiramate therapy resulted in an average weight loss of 7.73 kg compared to placebo.
Efficacy and Safety of Phentermine
- Study 5 found that longer-term users of phentermine experienced more weight loss, with patients using continuously for > 12 months losing 7.4% more than the referent group at 24 months.
- Study 6 suggests that phentermine use is associated with clinically significant weight loss in adults and that the medication is generally well tolerated.
- Study 4 reports that phentermine/topiramate has considerable benefit in reducing body weight, but increases the risk of nervous system-related adverse events.
Ozempic (Semaglutide) Efficacy
- Study 2 reports that semaglutide was associated with 11.4% greater weight loss compared to placebo, making it a potentially more effective option for weight loss compared to phentermine-topiramate.
- However, there is no direct comparison between Phentermine and Ozempic in the provided evidence, making it difficult to determine which medication is more effective for weight loss.