Abstract
<jats:p>The respiratory and gastrointestinal systems are vital for sustaining life by facilitating gas exchange, nutrient assimilation, and waste elimination. Pharmacological agents targeting these systems are essential in the management of a wide spectrum of diseases, including asthma, chronic obstructive pulmonary disease (COPD), peptic ulcer disease, gastroesophageal reflux disease (GERD), inflammatory bowel disease, and disorders of gastrointestinal motility. These drugs exert their therapeutic effects through complex mechanisms involving smooth muscle modulation, receptor-mediated signaling, enzyme inhibition, and regulation of inflammatory pathways. This chapter provides an extensive and advanced exploration of respiratory and gastrointestinal pharmacology, integrating structural and functional physiology with molecular mechanisms of drug action. It discusses bronchodilators, anti-inflammatory agents, mucolytics, antitussives, and emerging biologics in respiratory therapy, along with acid-suppressing agents, motility modifiers, antiemetics, and cytoprotective drugs in gastrointestinal pharmacology. Special emphasis is placed on signal transduction pathways, receptor selectivity, pharmacokinetic considerations, and clinical applications. The chapter also highlights adverse effects, drug interactions, and recent advances in therapy. Tables summarizing major drug classes and mechanisms are included to facilitate understanding.</jats:p>