This research project represents a coordinated attack involving a multidisciplinary approach upon the problem of drug dosage in infants and children. Pharmacokinetic data for a number frequently prescribed drugs will be obtained in common disease states seen in the pediatric age group, such as iron deficiency anemia, cystic fibrosis, nephrotic syndrome, asthma, renal insufficiency and intrauterine growth retardation. The age spectrum presented by these diseases and the disordered pathophysiology encountered in them will permit determination of the effects of age and disease as well as inheritance, acidosis, anemia, azotemia, hypoxia, hypoproteinemia, edema and malnutrition upon the pharmacokinetic parameters of absorption, distribution, metabolism and excretion. Drugs have been selected for study because they are representative of a spectrum of pharmacokinetic processes which are likely to be altered during disease states. They also constitute a large proportion of the drug classes used in pediatric practice. The techniques and approaches to this study have been developed in the laboratories of the professionals associated with the project. These personnel bring to the project not only complementary areas of expertise but also a proven record of having worked together fruitfully in the solution of several important problems concerning pediatric pharmacology. The data obtained in this research should not only enhance our knowledge of absorption, distribution, metabolism and excretion of drugs in the disease states which are being studied but also in the developing infant and child. From these data rationale approach to therapeutic dosage estimation will be made available.