Chapter 26: Autacoid Drugs That Mimic Endogenous Substances

The discussion primarily focuses on three major classes: biogenic amines like histamine and serotonin, fatty acid derivatives known as eicosanoids, and peptide signaling molecules such as endothelin-1. Histamine is detailed as a critical mediator of allergic reactions and gastric acid production, with a distinction made between first-generation H1 antagonists, which cross the blood-brain barrier to cause sedation, and second-generation agents that offer relief from allergies without affecting the central nervous system. The text also introduces newer agents like pitolisant, an H3 receptor antagonist used to manage narcolepsy. Turning to serotonin, the chapter outlines its diverse roles in the gut and brain, highlighting therapeutic interventions such as triptans for migraines and "setron" drugs for preventing nausea. A significant portion of the material is dedicated to the complex world of eicosanoids—including prostaglandins, thromboxanes, and leukotrienes—derived from fatty acids like arachidonic acid. Clinical applications for these substances are vast, ranging from alprostadil for neonatal heart defects and misoprostol for ulcer prevention to latanoprost for glaucoma management and epoprostenol for pulmonary arterial hypertension. Finally, the chapter addresses the role of endothelin-1 as a potent vasoconstrictor and the use of dual receptor antagonists like bosentan to treat vascular disorders. By examining the biosynthetic pathways and specific receptor interactions of these local hormones, this summary provides an essential framework for understanding how drugs can mimic or inhibit naturally occurring substances to treat conditions such as asthma, carcinoid syndrome, and inflammatory diseases.