Phentermine is a sympathomimetic amine anorectic that acts as a norepinephrine-releasing agent in the hypothalamus to suppress appetite. It is FDA-approved for short-term use (≤12 weeks) as an adjunct to lifestyle modification in patients with BMI ≥30 kg/m² or ≥27 kg/m² with comorbidities. Common side effects include increased heart rate, elevated blood pressure, insomnia, and dry mouth. It is a Schedule IV controlled substance due to potential for abuse.