The document discusses respiratory drugs used to treat bronchial asthma. It describes the pathogenesis of asthma and mechanisms of different drug classes including bronchodilators, anti-inflammatory agents, and other drugs. Bronchodilators like beta-2 agonists, methylxanthines, and antimuscarinics work to relax airway smooth muscle. Corticosteroids and other anti-inflammatory drugs reduce airway inflammation. Newer targeted therapies also show promise in treating asthma.