From the Guidelines
Phentermine should be used in conjunction with lifestyle modifications for adults with obesity or overweight with weight-related complications, as it has been suggested to be effective in achieving weight loss, with a low strength of recommendation and low quality of evidence 1. The use of phentermine, an appetite suppressant, is recommended for short-term weight loss in adults who are obese or overweight with weight-related health conditions.
Key Points to Consider
- Phentermine is typically prescribed at doses of 15-37.5 mg once daily, taken before breakfast or 1-2 hours after breakfast.
- It works by suppressing appetite through stimulating the central nervous system and increasing levels of norepinephrine in the brain.
- Treatment duration is usually limited to 12 weeks or less due to potential for tolerance and dependence.
- Common side effects include dry mouth, insomnia, constipation, increased heart rate, and elevated blood pressure.
- Phentermine should not be used by people with heart disease, hyperthyroidism, glaucoma, or those taking MAO inhibitors.
- It's classified as a controlled substance (Schedule IV) due to its chemical similarity to amphetamines and potential for abuse.
- For effective weight loss, phentermine should be used alongside a reduced-calorie diet and increased physical activity, not as a standalone treatment. Some important considerations for the use of phentermine include:
- Monitoring of blood pressure and heart rate while taking phentermine, as it can cause increases in these parameters 1.
- Avoidance of use in patients with a history of cardiovascular disease, due to the potential for adverse effects on the heart 1.
- Use of phentermine in conjunction with lifestyle modifications, such as a reduced-calorie diet and increased physical activity, for effective weight loss 1. According to a study published in 2022, the American Gastroenterological Association (AGA) suggests using phentermine with lifestyle modifications, compared with lifestyle modifications alone, for adults with obesity or overweight with weight-related complications, with a conditional strength of recommendation and low quality of evidence 1. In contrast, a study published in 2017 discussed the practical use of pharmacotherapy for obesity, including phentermine, and highlighted its effectiveness in achieving weight loss, but also noted the potential for side effects and the need for careful patient selection 1. However, the most recent and highest quality study, published in 2022, provides the strongest evidence for the use of phentermine in conjunction with lifestyle modifications for adults with obesity or overweight with weight-related complications 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, such as:
- Controlled hypertension
- Diabetes
- Hyperlipidemia It is indicated for short-term use (a few weeks) as an adjunct to a regimen of weight reduction based on exercise, behavioral modification, and caloric restriction 2, 2, 2.
From the Research
Use of Phentermine (Adipex) as an Appetite Suppressant
Phentermine is an internationally recognised amphetamine derivative with significant appetite-suppressing properties 3. The primary use of phentermine is for the short-term management of obesity, as indicated by various studies 3, 4, 5.
Mechanism of Action and Effects
The drug 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 6. Phentermine is often prescribed for short-term use due to its declining effect with time and its addiction potential 6, 4.
Clinical Applications and Efficacy
Clinical studies have shown that phentermine, alone or in combination with other medications like topiramate, can lead to significant weight loss in overweight and obese adults 4, 7. For example, the combination of phentermine and topiramate has been associated with a mean weight loss of 8-10% of the initial body weight 7.
Safety and Side Effects
However, the use of phentermine is also associated with potential side effects, including dry mouth, paraesthesia, constipation, insomnia, dizziness, and dysgeusia 7. Additionally, long-term use of phentermine may be associated with severe cardiovascular side effects, abuse, and dependence 3.
Key Points
- Phentermine is used for the short-term management of obesity due to its appetite-suppressing properties 3, 4.
- The drug has a potential for addiction and declining effect with time 6.
- Phentermine can be used in combination with other medications, such as topiramate, to enhance its efficacy 7.
- The use of phentermine is associated with various side effects, including dry mouth, paraesthesia, and constipation 7.