The role of therapeutic drug monitoring in childhood.

Therapeutic drug monitoring (TDM) can greatly improve the precision of drug therapy, provided 1) the analytical technique is sensitive, selective, and reproducable enough, 2) the pharmacokinetics of the drug is reasonably well known, and 3) the quantitative relation between kinetics and clinical effect is not too complicated. The TDM service must be supervised and further developed by a responsible group of experts, for example, a section or department of clinical pharmacology that should also provide service to help the physicians to take full advantage of the system. The appearance of active drug metabolites (for some drugs) and the considerable fluctuations in blood levels (in some patients) may complicate the interpretation. A cost-benefit analysis should continuously be made of the system; small, peripheral units for TDM may be too expensive to run.