From the Guidelines
Phentermine should be used in conjunction with lifestyle modifications for short-term weight loss in adults with obesity or overweight with weight-related complications, as suggested by the AGA with a conditional recommendation and low-quality evidence 1. The use of phentermine, an appetite suppressant, is recommended for adults with obesity or overweight with weight-related complications, as it has been shown to promote weight loss by activating the sympathetic nervous system and decreasing food intake 1.
Key Considerations
- Phentermine is typically prescribed at doses of 15-37.5 mg once daily, taken before breakfast or 1-2 hours after breakfast 1.
- It should only be used for 12 weeks or less due to the potential for dependence and diminishing effectiveness over time 1.
- Common side effects include dry mouth, insomnia, constipation, increased heart rate, and elevated blood pressure 1.
- Phentermine is contraindicated in patients with cardiovascular disease, hyperthyroidism, glaucoma, history of drug abuse, or during pregnancy 1.
Implementation
- Patients should be monitored regularly for blood pressure changes and other potential side effects while using this medication 1.
- Phentermine should be used alongside diet and exercise modifications, not as a standalone treatment 1.
- Patients should avoid taking it late in the day to prevent sleep disturbances 1.
Evidence Summary
The AGA suggests using phentermine with lifestyle modifications, compared with lifestyle modifications alone, with a conditional recommendation and low-quality evidence 1. A systematic review and meta-analysis of 31 RCTs assessing lifestyle vs control interventions showed a pooled estimate of 3.6-kg weight loss at 1 year and 2.5 kg at 3 years 1.
Patient Selection
Appropriate candidates for phentermine include patients with obesity who need assistance with appetite suppression, but it should be used with caution in patients with anxiety or insomnia, and avoided in patients with active or unstable coronary disease, or uncontrolled hypertension 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). Phentermine Hydrochloride is a sympathomimetic amine anorectic indicated as a short-term adjunct (a few weeks) 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 use of Phentermine (Adipex) is as an appetite suppressant for the management of exogenous obesity in patients with a body mass index (BMI) 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. The recommended use is as a short-term adjunct in a regimen of weight reduction based on exercise, behavioral modification, and caloric restriction 2, 2.
Key points:
- Indication: Short-term management of exogenous obesity
- Patient selection: BMI greater than or equal to 30 kg/m^2 or greater than or equal to 27 kg/m^2 with other risk factors
- Use: As an adjunct to a weight reduction regimen based on exercise, behavioral modification, and caloric restriction
From the Research
Use of Phentermine
The use of Phentermine, an appetite suppressant, is indicated for the short-term management of obesity 3. It is an internationally recognised amphetamine derivative with significant appetite-suppressing properties.
Mechanism of Action
Phentermine acts as a potent substrate at the norepinephrine transporter, simultaneously promoting its release, and has a weaker activity at the dopamine transporter, whereas its activity towards the serotonin transporter is negligible 4.
Clinical Use
Phentermine is approved for short-term obesity treatment in conjunction with lifestyle modifications to decrease cardiovascular risk 5. It is classified as a centrally acting drug, which regulates appetite in the brain 6.
Efficacy and Safety
Recent research suggests that phentermine use is associated with clinically significant weight loss in adults and that the medication is generally well tolerated 7. Large-scale observational studies evaluating phentermine's safety have not identified an increased risk of cardiovascular events or elevations in blood pressure 7.
Key Points
- Phentermine is used for the short-term management of obesity
- It has significant appetite-suppressing properties
- It acts as a potent substrate at the norepinephrine transporter
- It is approved for short-term obesity treatment in conjunction with lifestyle modifications
- It is generally well tolerated, with no increased risk of cardiovascular events or elevations in blood pressure
- There is no data to support the notion that phentermine is addictive 7
Potential Risks
- Long-term use may be associated with severe cardiovascular side-effects, abuse, and dependence 3
- Potential drug-drug interactions (PDDIs) may result in adverse drug reactions (ADRs) 3
- Case reports propose that phentermine usage might be associated with severe health risks due to hypertension, vasoconstriction, and vasculopathy 4