When is phentermine (Adipex-P) used?

From the Guidelines

Phentermine (Adipex-P) is used in adults with obesity or overweight with weight-related complications, in conjunction with lifestyle modifications, to aid in weight loss.

Key Points

• Phentermine is suggested for use in adults with obesity or overweight with weight-related complications, along with lifestyle interventions, compared to lifestyle interventions alone 1.
• The medication is approved by the FDA for short-term use (12 weeks), but many practitioners use it for longer durations in an off-label fashion 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 the medication 1.
• The recommended dosage of phentermine is 15 to 37.5 mg orally once daily in the morning, with potential side effects including dry mouth, difficulty sleeping, dizziness, and irritability 1.
• Appropriate candidates for phentermine include patients with obesity who need assistance with appetite suppression, but it should not be used in patients with anxiety or insomnia, or those taking monoamine oxidase inhibitors or other sympathomimetic amines 1.
• Phentermine is a Schedule IV controlled substance, but it is associated with a low risk of dependency or abuse 1.
• Recent reviews have found that phentermine is not associated with an increased risk of major adverse cardiac events compared to usual care 1.

From the FDA Drug Label

The usual adult dose is 15 mg to 30 mg at approximately 2 hours after breakfast for appetite control. Phentermine is not recommended for use in patients 16 years of age and under.

Phentermine (Adipex-P) is used for:

• Exogenous Obesity: Phentermine is used as an appetite suppressant for weight loss in adults.
• Appetite Control: The medication is typically taken at approximately 2 hours after breakfast to control appetite. Key Points:
• The medication is not recommended for patients under 16 years of age.
• The usual adult dose is 15 mg to 30 mg daily 2.

From the Research

Phentermine Usage

Phentermine, also known as Adipex-P, is used for the short-term management of obesity, as indicated by 3. The medication is an amphetamine derivative with significant appetite-suppressing properties.

Indications and Usage

• Phentermine is indicated for the short-term management of obesity, typically for periods not exceeding 12 consecutive weeks 3.
• The medication is often prescribed for off-label indications, increasing the risk of adverse drug events and drug-drug interactions 3.
• Phentermine may be considered for long-term use in selected patients, if consistent with local regulatory statutes, although there is limited research to support its efficacy and safety in long-term treatment 4.

Combination Therapies

• Phentermine is also used in combination with topiramate, an antiepileptic drug, for the management of obesity, with evidence suggesting that this combination offers synergistic potential for effective and sustained weight loss 5.
• The fixed-dose combination of phentermine and extended-release topiramate has been approved by the FDA for the chronic treatment of overweight/obese adults as an adjunct to lifestyle intervention 5, 6.

Safety Considerations

• Long-term use of phentermine may be associated with severe cardiovascular side effects, abuse, and dependence, although some studies suggest that the medication is generally well-tolerated and not addictive 3, 4, 7.
• Phentermine may interact with other medications, increasing the risk of adverse drug reactions, particularly when used in combination with other pharmaceutical constituents 3.