Pharmacokinetics of Understudied Drugs Administered to Children Per Standard of Care

The purpose of this study is to characterize the PK ( Pharmacokinetics) of understudied drugs administered to children per standard of care as prescribed by their treating caregiver. This will be accomplished by the collection of biological samples during the time of drug administration per standard of care as prescribed by the caregiver. The prescribing of drugs to children will not be part of this protocol. Aim #1: Evaluate the PK of understudied drugs currently being administered to children. Hypothesis #1: The PK of understudied drugs in children will differ from adults and within children according to pediatric age groups or special population. Aim #2: Explore the pharmacodynamics (PD) of understudied drugs currently being administered to children. Hypothesis #2: The PD of targeted drugs in children will differ from adults. Aim #3: Evaluate the influence of genetic factors, metabolic and protein profiles on therapeutic exposure. Hypothesis #3: Genetic polymorphisms in drug metabolizing enzymes and metabolic and proteomic profiles will impact drug exposure in children.