Cefadroxil and Cephalexin Drug Levels and Dosing in Pediatric Musculoskeletal Infections

The goal of this study is to figure out the best doses for two antibiotics (called cefadroxil and cephalexin) when they are used to treat bone, joint, or muscle infections in children. In order to do this, the study will collect data about children admitted to Children's Hospital Colorado who have these types of infections. During the study, these patients will receive doses by mouth of each of these antibiotics, in addition to an IV antibiotic (given through a vein) used to treat their infection. After the dose of the first antibiotic, blood samples will be drawn every few hours to measure how much of the drug is still in their body, until it is all gone. After the first antibiotic is out of the patient's body, the same will be done for the second antibiotic. Measurements, in the lab, of how much of these antibiotics are needed to kill the most common bacteria causing these infections, which is a type of "Staph" bacteria called "MSSA", will be taken. Finally, the blood levels of the antibiotics and the information from the lab tests about the Staph bacteria will be used to calculate how much and how often of the antibiotic should be given to children with bone, joint, or muscle infections. Currently, these types of infections are treated with an antibiotic that children have to take four times every day. The goal of this study is to find an antibiotic that children can take only two or three times per day.