Pharmacology is a rapidly advancing science. The essence of rational pharmacotherapeutics is to maximize the efficacy of a pharmaceutical interventional product for a specific indication, with a simultaneous minimization of its adverse effects. With this primary objective in mind, research and development activities of pharmaceutical companies and other healthcare research organizations focus on the development and screening of new chemical entities (NCE). Once a definite pharmacological action of the NCE has been discovered, which is expected to be of satisfactory therapeutic value, the molecule is taken for a thorough pre-clinical animal testing in order to determine its feasibility for human clinical trials. Positive outcomes of the animal studies facilitate the submission of an Investigational New Drug (IND) application with the requisite drug regulatory authority of that particular country. The molecule then undergoes Phase I-III Clinical Trials before it can get a marketing approval. Alternatively, an existing molecule can be modified as per the structure activity relationships to enhance its efficacy or safety. There are numerous examples of structural modifications yielding much better pharmacokinetic and or pharmacodynamic profiles. Introduction of new and better drugs ensure a continuous improvement in the management of patients with all types of ailments. A post marketing surveillance facilitates evidence based medicine, so also in the detection, assessment and analysis of adverse events which constitutes the discipline of Pharmacovigilance.