Editorial [ Use of Mass Spectrometry for Drug Metabolism StudiesGuest Editor: Walter A. Korfmacher ]

The impetus for this special edition stems from the realization that mass spectrometry is now an indispensable toolthat is needed for all the phases of new drug discovery and development. Mass spectrometry is first used for thestructural characterization of all new compounds and then for their pharmaceutical profiling. The new compoundsthat show activity in a high throughput screening assay are then brought to a discovery drug metabolism group forfurther evaluation. It can be stated that at least one mass spectrometry group is an essential requirement for asuccessful drug metabolism department. Mass spectrometry has become the premier analytical tool for the multiplein vitro and in vivo absorption, distribution, metabolism and excretion (ADME) assays. These assays use massspectrometry for both quantitative and qualitative applications. One of the most common uses of HPLC-MS/MSsystems is for bioanalytical assays of both preclinical and clinical pharmacokinetic (PK) samples. Anotherimportant application area is the identification of drug metabolites; new software tools and new MS instrumentationhas been developed to improve our ability to both detect and identify these metabolites. In addition, the newapplication area of biomarker discovery and measurement is becoming a very important part of the new drugdevelopment process. Furthermore, mass spectrometry is continuing to evolve as evidenced by new ionizationsources (nano-ESI) and new types of hybrid mass spectrometers (e.g., the Q-Trap MS and the LTQ-FTMS systems)that have become available in the last few years. I have selected experts in various fields of mass spectrometry towrite the reviews and mini-reviews that you will find in this special edition. I want to thank Chandra Prakash forsuggesting this special edition and thank the authors of these reviews and mini-reviews for their excellentmanuscripts. Together these papers and their references provide a good overview of the use of mass spectrometry incurrent drug metabolism applications.