Pharmacoepidemiology is a discipline of medicine that studies the use and effects of medications in large groups of people. It allows us to estimate the probability o f good effects of a drug in a population as well as the probability of contradicting effects. It can be thought of as a science that connects clinical pharmacology and epidemiology. Pharmacoepidemiology focuses on clinical patient outcomes from therapeutics by employing a variety of clinical epidemiology techniques to better understand the origins of beneficial and harmful drug effects, impacts of genetic alterations on drug effect , , duration-response relationships, clinical effects of drug-drug interactions, and the effects of medication non-adherence. Pharmacovigilance is a branch of pharmacoepidemiology that entails ongoing population surveillance for adverse effects and drug interactions and various safety issues that have arisen with medications that are already on the market. Pharmacoepidemiology also encompasses the planning and evaluation of population-based campaigns to improve pharmaceutical use.