Background The rapid and major advances being made in epigenetics are impacting pharmacology, giving rise to new sub-disciplines in pharmacology, pharmacoepigenetics, the study of the epigenetic basis of variation in response to drugs; and pharmacoepigenomics, the application of pharmacoepigenetics on a genome-wide scale. Methods This article highlights the following aspects of pharmacoepigenetics and pharmacoepigenomics: epigenetic therapy, the role of epigenetics in pharmacokinetics, the relevance of epigenetics to adverse drug reactions, personalized medicine, drug addiction, and drug resistance, and the use of epigenetic biomarkers in drug therapy. Results Epigenetics is having an increasing impact on several areas of pharmacology. Conclusion Pharmacoepigenetics and pharmacoepigenomics are new sub-disciplines in pharmacology and are likely to have an increasing impact on the use of drugs in clinical practice.