This book has been written with the aim of giving an overview of the scientific developments which have occurred in mediators pharmacology. Pharmacology can be defined as a discipline of paramedical sciences that teaches how the use of drugs can bring about changes from pathological to physiological states. Mediators pharmacology is a subdivision of pharmacology which teaches the functions of molecules released in the body and produce profound pharmacological effects. The sustained release or deficiency of these mediators may result in pathological conditions. Agonists or antagonists of these mediators are novel therapeutic agents with potential clinical benefits. This book has not been intended to be a textbook of pharmacology or therapeutics and does not therefore describe the use of drugs in the treatment of diseases. Furthermore, this book is intended for postgraduates, higher level students in medicine, pharmacy, veterinary medicine, physiology, pharmacology, and research institutions.