Pharmacoepidemiology is the study of the use and effects of drugs in large numbers of people. It is a growing discipline that applies epidemiological techniques to study drug use in a large population. Just as the term implies, pharmacoepidemiology combines clinical pharmacology with epidemiology. Pharmacology is the study of the effects of medications in humans. It pertains to using pharmacokinetics and pharmacodynamics of a patient to predict the drug effect on a patient. Epidemiology is the study of the factors that determine the occurrence and distribution of diseases in populations. Epidemiologists study how much disease is in a given area, who gets it, and what specific factors put individuals at risk. Epidemiology can often be divided into infectious and chronic disease epidemiology. Chronic disease epidemiology is more dependent on complex sampling and statistical methods; which are often used in pharmacoepidemiology studies to evaluate drug exposure over time. By combining the interest of pharmacology and epidemiology, a pharmacoepidemiologist applies epidemiology principles to study the effects of medications in human populations.