This project was conceived in 1994 to help increase the number and percentage of drugs which are labeled for pediatric use (currently approximately 75 percent are not labeled for pediatric use) and to increase the knowledge of clinical pharmacology that is so important to intelligent, safe drug use in infants and children. The scope of the PPRU grant is to provide an organizational and operational infrastructure at UCSD and Children's Hospital of San Diego to implement the following specific aims: 1. To provide a locus for the conduct of studies in bioavailability, formulations, drug metabolism, pharmacokinetics, pharmacodynamics, safety and effectiveness of new drugs and drugs already in the market. These studies may be investigator initiated or they may originate with pharmaceutical companies or Contract Research Organizations (CRO's). 2. To gather or promote the accrual of the necessary clinical data for pediatric age-specific labeling of drugs. 3. To conduct research on new pediatric therapeutic modalities, including: A. Molecular approaches to the treatment of diseases, B. Application of new technology to pharmacodynamic studies and drug delivery systems, and C. Development of pediatric formulations, and d) validation of new endpoints or surrogate markers. 4. To conduct studies on the developmental characteristics and genetic polymorphism of drug metabolizing enzymes, pharmacokinetic modeling, and simulation technology. 5. To provide a teaching environment in which pediatricians, pharmacists, nurses and others can gain supervised experience in pediatric clinical trials and training in evidence-based pediatric pharmacology.