From the Guidelines
Phentermine (Adipex) should be prescribed to patients with a BMI of 30 kg/m2 or a BMI of 27 kg/m2 with weight-related comorbidities.
Key Points
- The decision to prescribe phentermine should be based on the patient's individual clinical characteristics and the presence of weight-related comorbidities such as hypertension, type 2 diabetes, dyslipidemia, and obstructive sleep apnea 1.
- According to the American Heart Association, pharmacotherapy, including phentermine, can be considered for patients with a BMI ≥ 30 kg/m2 or a BMI between 27 and 29.9 kg/m2 with an obesity-related medical complication 1.
- The Mexican clinical practice guidelines for adult overweight and obesity management recommend considering pharmacotherapy, including phentermine, for patients with a BMI ≥ 27 kg/m2 with related adiposity-related comorbidities or for patients with a BMI ≥ 30 kg/m2, in conjunction with nutritional counseling, psychological support, and physical activity prescription 1.
- A study published in Obesity Reviews suggests that pharmacotherapy, including phentermine, may be used as an adjunct therapy to lifestyle modification to improve or maintain weight loss and to control obesity-related complications in adults with a BMI ≥ 30 kg/m2 or BMI ≥ 27 kg/m2 with at least one obesity-related complication 1.
Dosage and Administration
- 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 1.
- For some patients, a quarter tablet (9.375 mg) or a half tablet (18.75 mg) may be adequate, and a split dose of a half tablet 2 times daily is also an option 1.
From the FDA Drug Label
Phentermine Hydrochloride, USP 15 mg and 30 mg is indicated as a short-term (a few weeks) adjunct in a regimen of weight reduction based on exercise, behavioral modification and caloric restriction in the management of exogenous obesity for patients with an initial body mass index greater than or equal to 30 kg/m 2, or greater than or equal to 27 kg/m 2 in the presence of other risk factors (e.g., controlled hypertension, diabetes, hyperlipidemia).
The Body Mass Index (BMI) to prescribe Adipex (Phentermine) is:
- greater than or equal to 30 kg/m²
- or greater than or equal to 27 kg/m² in the presence of other risk factors (e.g., controlled hypertension, diabetes, hyperlipidemia) 2
From the Research
Body Mass Index (BMI) for Prescribing Adipex (Phentermine)
- The BMI for prescribing Adipex (Phentermine) is typically ≥30 kg/m2, as stated in the study 3.
- However, it can also be prescribed for individuals with a BMI ≥27 kg/m2 with at least one obesity-related comorbidity, as mentioned in the studies 4 and 5.
- The studies 6 and 7 also support the use of phentermine for individuals with a BMI ≥30 kg/m2 or ≥27 kg/m2 with comorbidities.
Key Findings
- Phentermine can be used to achieve significant weight loss when combined with a very-low-calorie diet (VLCD) 3.
- The combination of phentermine and topiramate can cause appetite suppression and enhanced satiety, leading to greater weight loss 5.
- The use of phentermine-topiramate extended release in combination with sleeve gastrectomy may increase the odds of achieving a BMI <40 at 2 years postoperatively in patients with a BMI ≥50 kg/m2 7.