[Rational posology and drug dosage].

Serum level monitoring of drugs allows an optimal drug therapy, because it can take into account individual pharmacokinetic (and metabolic) variations. Some special conditions in drugs and in patients are highly suggestive of drug monitoring. These include mainly physiological but also pharmacological situations and apply to drugs with low therapeutic indices. However, for some drugs, highly bound to proteins or to blood cells, another more specific measurements will take in the future the place of serum level monitoring.