Pharmacology and toxicology of infant skin

Cutaneous metabolism and pharmacology have been the focus of increased scientific inquiry in the past 2 decades. However, in the past few years, attention has been focused specifically on the effects of topically applied drugs in infants as different qualitatively or quantitatively from their effects in adults. Prior to 1972, it was known that brain damage occurred in animals with prolonged blood levels of 1μg/ml hexachlorophene, and that washing newborn babies with a standard 3% hexachlorophene liquid soap for 3-5 days resulted in significant blood levels of the compound. However, this knowledge was not disseminated widely enough to prevent the tragic deaths of infants after the use of baby powder contaminated with 6.6% hexachlorophene. This incident highlighted the need for increased understanding of drug effects not only from the viewpoint of the skin as a target organ, but also of percutaneous penetration and resultant blood levels; the affinity of other body tissues for drugs and their metabolites; metabolites which may result from the effect of the skin itself acting on the drug; and in infant's much greater ratio of surface area to body weight, allowing the infant to percutaneously absorb proportionately greater quantities of topical medication than an adult. Athough tissue distribution of most drugs has not been studied in infants, it is known that such distribution often depends on age. For example, in infants and children with a given plasma level, of drugs such as barbiturates, morphine and tetracycline, the brain tissue level may exceed that of the adult. Thus, drugs and chemicals that penetrate infant skin produce effects different than those penetrating adult skin.