Antimicrobial therapy and the neonate.

The newborn is particularly susceptible to bacterial infection because of its underdeveloped immune system. The newborn's inability to localize infection can also delay diagnosis by altering the manifestations of infection. Anti-microbial therapy is complicated, however, by the immaturity and rapid changes in metabolic and physiologic functions during the first weeks of life. Diminished renal function and activity of some hepatic enzymes alter the half-lives of various drugs, making extrapolation from adult dosage impossible. For some drugs there is also a difference in the rate of intramuscular absorption in the newborn as compared with adults and older children. Disease itself may also alter physiologic processes involved in metabolism, bioavailability, and absorption of a drug. This study presents pharmacokinetic data and dose information for penicillins, cephalosporins, aminoglycosides, and chloramphenicol in neonates and infants at different gestational and chronologic ages.