Alternative sampling strategies for therapeutic drug monitoring

During recent years, increasing attention has been given to personalized medicine to effect optimal patient treatment. This concept will remain of utmost importance and is likely to become an essential part of modern patient health care. An extremely valuable aspect of personalized medicine is undoubtedly therapeutic drug monitoring (TDM). Unfortunately, the assessment of therapy adherence and adequacy via the measurement of therapeutic drug levels can be difficult or even impossible to perform in certain patient populations and settings when using traditional sampling approaches. Therefore, the collection of alternative matrices is extensively evaluated for TDM purposes. Examples of these matrices include dried blood spots, dried blood microsamples, dried plasma spots, other dried matrix spots, oral fluid, tears, hair, interstitial fluid, exhaled breath, sweat, and nasal mucus. This chapter highlights the advantages, challenges, and limitations of each of these alternative matrices and discusses select applications, with particular attention to applications in special patient populations such as neonates, children, elderly, and pregnant women. In addition, the hurdles that impede routine implementation of alternative matrix analysis for TDM purposes are outlined, as well as current and potential future developments that may contribute to the more widespread acceptance of alternative matrix analysis for TDM in the (near) future.