Deals with principles of Ayurvedic pharmacognosy and pharmacology with a special focus on identification of controversial drugs, adulterants and substitutes used in Ayurvedic practice. Ayurveda has developed a unique approach to understanding pharmacology of natural substances through meticulous analysis of taste, physico-chemical properties, potency and bio-transformation of the drug. Ayurveda traces the pathway of drug action right from the point of its ingestion through various stages of its digestion and metabolism to the point of its excretion from the body. Ayurveda understands drug action as the net result what happens when the drug acts on the body and the body acts on the drug. Dravyaguna deals knowledge of nomenclature (namajnana), pharmacognosy (rupajnana), pharmacology (gunajnana) and pharmacotherapeutics (yuktijnana). The hallmark of Ayurvedic pharmacology is its theoretical framework that attempts to understand complex interactions between various ingredients in a formulation that work in synergestic manner to produce a pharmacotherapeutic action that initiates the process of healing.