What is the efficacy of weight loss with Phentermine (Adipex) and Topiramate (Topamax)?

From the Guidelines

Combining Adipex (phentermine) and Topamax (topiramate) can be effective for weight loss, though this combination should only be used under close medical supervision. Phentermine is a short-term appetite suppressant that stimulates the central nervous system, while topiramate, an anticonvulsant, may reduce appetite and increase feelings of fullness, as noted in the white paper by the American Gastroenterological Association 1. Typically, phentermine is prescribed at 15-37.5 mg once daily in the morning, while topiramate often starts at 25 mg daily and may increase gradually to 100 mg daily, divided into two doses. This combination works by affecting different pathways in the brain that control hunger and satiety.

Key Considerations

• The recommended dosage of phentermine is 15–37.5 mg orally once daily, but dosage should be individualized to achieve adequate response with the lowest effective dose, as stated in the study 1.
• A fixed-dose combination of phentermine and topiramate ER, known as Qsymia, is available and has been approved by the FDA for chronic weight management, with a recommended gradual dose escalation to minimize risks and adverse events 1.
• Side effects can include dry mouth, insomnia, dizziness, constipation, and mood changes.
• The combination is not FDA-approved specifically for weight loss, though Qsymia is, and these medications should be used alongside lifestyle modifications including diet and exercise.
• These medications are generally recommended for individuals with BMI ≥30 or BMI ≥27 with weight-related conditions, and regular monitoring by a healthcare provider is essential to assess effectiveness and manage potential side effects.

Monitoring and Lifestyle Modifications

• Patients should be advised to follow a diet with approximately 30% of calories from fat and take a multivitamin to ensure adequate nutrition, as certain medications like orlistat can decrease the absorption of fat-soluble vitamins 1.
• Regular monitoring of weight loss, as well as potential side effects, is crucial to determine the effectiveness of the treatment and make any necessary adjustments to the dosage or medication regimen.

From the Research

Weight Loss with Adipex and Topamax

• The combination of phentermine (Adipex) and topiramate (Topamax) has been shown to be effective for weight loss in obese individuals 2, 3.
• Studies have demonstrated that this combination can lead to an average weight loss of 10% of initial weight, which is approximately 8% more than placebo 2.
• The use of phentermine and topiramate extended release (ER) has been approved by the FDA for chronic weight management, as an adjunct to lifestyle modification 2, 3.
• Lifestyle modifications, such as a reduced-calorie diet, increased physical activity, and behavior therapy, are also essential for weight loss and should be used in conjunction with pharmacotherapy 4, 5, 6.
• The combination of phentermine and topiramate ER has been shown to have beneficial effects on cardiometabolic risk, although longer-term cardiovascular safety data are required 3.

Key Findings

• Weight loss of ≥ 5% of initial weight can improve quality of life and risk factors for cardiovascular disease (CVD) in obese individuals 2.
• Phentermine-topiramate ER has been associated with increased heart rate, and its use must be cautious in women of child-bearing age due to an increased risk to infants of oral cleft 2.
• Intensive lifestyle interventions, consisting of a reduced-calorie diet, increased physical activity, and behavior therapy, can lead to significant weight loss and improvements in health and quality of life 6.