Clenbuterol is a beta-2 adrenergic agonist that stimulates beta-2 receptors in the lungs, leading to airway relaxation and improved airflow. Besides its bronchodilatory effects, it has thermogenic properties, meaning it can increase metabolic rate and promote fat burning. Clenbuterol is not approved by the FDA for human use in the United States and should only be used under medical guidance where permitted. Misuse can lead to serious health risks.