Antibiotic Dosage in Newborn and Premature Infants

The intelligent use of a drug in any patient demands adequate knowledge of the mechanisms of absorption, metabolism, and excretion of the given agent, as well as its therapeutic actions and possible untoward effects. When antibiotic therapy is undertaken, another variable, the microorganism, is introduced. Determination of the therapeutic dosage of an antibiotic on a rational basis, which is mandatory in any case, requires recognition of the potential interplay among these entities. After absorption, the concentration of an antibiotic agent is determined mainly by metabolism (detoxication) and excretion, which are fairly constant in the healthy adult, child, and older infant. In practice, therefore, antibiotic dosages for those beyond the neonatal period are usually achieved by adjusting adult dosage on the basis of age (Young's rule), body weight (or correction for body weight according to Clark's rule), or surface area. However, because the neonatal period is one of changing body and