The medicinal sciences have always aimed at an increased effort to increase the patient safety and reduce medical errors. These errors are mainly caused due to therapeutic failure and adverse drug reactions which arise as a result of incorrect dosing of the routinely prescribed drugs. The drugs are metabolized by drug metabolizing enzymes of which the Cytochrome P450 enzyme forms a major class. It is now being observed that with the descriptions of genetic polymorphism in the drug metabolizing enzymes, the field of pharmacogenetics may improve medical care through a reduction in adverse drug reactions oriented errors. The status of these drug metabolizing enzymes can be characterized using phenotyping studies which categorizes the population into poor, extensive or ultra-extensive metabolizers. Such a division of population based on their metabolic status will be of immense help to the medical authorities in deciding the drug dose. This paper reviews the field of Cytochrome P450 (CYP) genetics and explores factors that impact the utility of this information in clinical practice to avoid incidences occurring due to incorrect metabolism of the routinely prescribed drugs.