How to prescribe phentermine (Adipex) for weight loss?

From the Guidelines

Phentermine should be prescribed at a dose of 15-37.5 mg orally once daily in the morning for a maximum duration of 12 weeks, with careful consideration of the patient's medical history and regular monitoring of blood pressure, heart rate, and weight, as recommended by the most recent guideline 1. When prescribing generic phentermine for weight loss, it is essential to consider the patient's overall health and medical history. According to the guideline, phentermine monotherapy is approved by the FDA for short-term use (12 weeks), but many practitioners use it longer than 12 weeks in an off-label fashion 1.

Key Considerations

• The recommended dosage of phentermine is 15 to 37.5 mg orally once daily in the morning, as stated in the study 1.
• Phentermine should be avoided in patients with a history of cardiovascular disease, and blood pressure and heart rate should be monitored periodically while taking phentermine 1.
• Patients who have anxiety or insomnia might feel their condition is exacerbated by phentermine, and would not be ideal candidates 1.
• Regular monitoring of blood pressure, heart rate, and weight is necessary, with discontinuation if 2kg weight loss isn't achieved in the first month or if side effects become problematic.

Potential Side Effects

• Common side effects of phentermine include dry mouth, difficulty sleeping, dizziness, and irritability, as reported in the study 1.
• Phentermine is contraindicated in patients with cardiovascular disease, hyperthyroidism, glaucoma, history of drug abuse, pregnancy, and in those taking MAOIs.

Lifestyle Modifications

• Patients should combine medication with calorie reduction and increased physical activity for optimal results, as recommended by the guideline 1.
• A lifestyle strategy, including dietary changes and increased physical activity, is essential for achieving and maintaining weight loss, as discussed in the study 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). Dosage should be individualized to obtain an adequate response with the lowest effective dose. The usual adult dose is 15 mg to 30 mg at approximately 2 hours after breakfast for appetite control.

To prescribe generic phentermine for weight loss:

• Indications: Use as a short-term adjunct in a regimen of weight reduction based on exercise, behavioral modification, and caloric restriction for patients with an initial body mass index (BMI) ≥ 30 kg/m² or ≥ 27 kg/m² with other risk factors.
• Dosage: Individualize the dose to obtain an adequate response with the lowest effective dose. The usual adult dose is 15 mg to 30 mg at approximately 2 hours after breakfast for appetite control.
• Administration: Administer one capsule (30 mg) daily, as needed, to control appetite for 12 to 14 hours. Avoid late evening medication due to the possibility of resulting insomnia.
• Contraindications: Do not use in patients with a history of cardiovascular disease, during or within 14 days following the administration of monoamine oxidase inhibitors, hyperthyroidism, glaucoma, agitated states, history of drug abuse, pregnancy, or nursing.
• Warnings and Precautions: Monitor for primary pulmonary hypertension, valvular heart disease, development of tolerance, and risk of abuse and dependence 2.

From the Research

Prescribing Generic Phentermine for Weight Loss

To prescribe generic phentermine for weight loss, consider the following:

• The patient should have a body mass index (BMI) of 30 kg/m2 or greater, or a BMI of 27 kg/m2 or greater with at least one coexisting condition, such as type 2 diabetes, hypertension, hyperlipidemia, or sleep apnea 3.
• Lifestyle modifications should be continued and emphasized throughout treatment, as adjunctive pharmacotherapy produces greater weight loss and weight loss maintenance than lifestyle interventions alone 3.
• Phentermine is one of the five drugs approved for weight management in adults, and drug therapy should be customized to the individual patient, depending on needs, contraindications, and cost 3.
• The benefits of phentermine should be assessed regularly, and a different drug should be considered if at least 5% of body weight is not lost by 3 months of therapy 3.

Considerations for Patients with Cardiovascular Disease

• In patients with obesity and cardiovascular disease (CVD), sympathomimetic medications like phentermine should be avoided due to potential safety concerns 4.
• Instead, medications like orlistat, lorcaserin, and liraglutide may be more appropriate options for patients with CVD, as they have been shown to be safer in this population 4.
• However, more studies are needed to assess the safety and efficacy of weight loss medications in patients with CVD 5, 4.

Efficacy and Safety of Phentermine

• Phentermine has been shown to be effective for weight loss, particularly when combined with extended-release topiramate 6.
• However, the use of phentermine/topiramate has been associated with adverse effects, such as dry mouth, constipation, and headache 7.
• The long-term effects of phentermine on mortality and morbidity are not well established, and more studies are needed to assess its safety and efficacy in different populations 7.