PEDIATRIC DRUG DOSAGE
Because of differences in pharmacokinetics in infants and chil-dren, simple proportionate reduction in the adult dose may not be adequate to determine a safe and effective pediatric dose. The most reliable pediatric dose information is usually that provided by the manufacturer in the package insert. However, such infor-mation is not available for the majority of products, even when studies have been published in the medical literature, reflecting the reluctance of manufacturers to label their products for chil-dren. Recently, the FDA has moved toward more explicit expecta-tions that manufacturers test their new products in infants and children. Still, most drugs in the common formularies, eg, Physicians’ Desk Reference, are not specifically approved for chil-dren, in part because manufacturers often lack the economic incentive to evaluate drugs for use in the pediatric market.
Most drugs approved for use in children have recommended pediatric doses, generally stated as milligrams per kilogram or per pound. In the absence of explicit pediatric dose recommendations, an approximation can be made by any of several methods based on age, weight, or surface area. These rules are not precise and should not be used if the manufacturer provides a pediatric dose. When pediatric doses are calculated (either from one of the meth-ods set forth below or from a manufacturer’s dose), the pediatric dose should never exceed the adult dose.
With the current epidemic of child obesity, a fresh and careful look at pediatric drug dosing will be needed. Studies in adults indicate that dosing based on per kilogram of body weight may constitute overdosing, because most drugs are distributed based on lean body weight, rather than total (obese) weight.
Surface Area, Age, & Weight
Calculations of dosage based on age or weight are con-servative and tend to underestimate the required dose. Doses based on surface area (Table 59–6) are more likely to be adequate.
Age (Young’s rule):
In spite of these approximations, only by conducting studies in children can safe and effective doses for a given age group and condition be determined.