Drug used for obesity –
**Core Concept**
Phentermine is a centrally acting sympathomimetic amine, which works by stimulating the release of norepinephrine, thereby increasing satiety and decreasing appetite. This is a key concept in the pharmacological treatment of obesity.
**Why the Correct Answer is Right**
Phentermine is used as an adjunct in the treatment of obesity, particularly in patients with BMI ≥ 30 kg/m² or those with a BMI ≥ 27 kg/m² with at least one weight-related condition. It is most effective when combined with a reduced-calorie diet and increased physical activity. By stimulating the release of norepinephrine, phentermine increases the activity of the hypothalamus, which in turn decreases appetite and increases feelings of fullness.
**Why Each Wrong Option is Incorrect**
**Option A:** Orlistat, a lipase inhibitor, works by preventing the absorption of dietary fats, but it does not decrease appetite or increase satiety like phentermine does.
**Option B:** Phentermine is not a serotonin-norepinephrine reuptake inhibitor (SNRI) like venlafaxine, which is used to treat depression and anxiety disorders.
**Option C:** Phentermine is not a glucagon-like peptide-1 (GLP-1) receptor agonist like exenatide, which is used to treat type 2 diabetes.
**Clinical Pearl / High-Yield Fact**
When prescribing phentermine for obesity, it's essential to monitor patients for potential side effects such as insomnia, anxiety, and hypertension. Additionally, phentermine should not be used in patients with a history of cardiovascular disease or those taking certain medications like MAOIs or sympathomimetics.
**Correct Answer: C. Phentermine**