[Special pharmacokinetic aspects in newborns and young infants]

The safety of drug therapy in the newborn period and early infancy is endangered for two main reasons: 1. The relative distribution volume of drugs during maturation and in pathological states varies greatly and thus makes conventional dosage in short-term therapy ineffective. 2. During early childhood, the rate of elimination of many drugs is slow hence there is a risk of overdosage in long-term therapy with doses considered safe in older children. The example of two drugs demonstrates, that the course of blood levels is not only dependent on the elimination half life and on the relative distribution volume, but may also be modified to a large extent by the process of invasion. This increases the risk of iron-dextrane but contributes to the safety of Cephalexine. If drug therapy is to be safe and effective in childhood at least the basic elements of a most simple pharmacokinetical model consisting of Invasion, Volume of Distribution and Elimination must be known as can be shown by the mathematical extrapolation of blood level curves gained from single applications for long-therm therapy.