[Assays of serum concentrations in drug intoxications]

Drug assays in serum and urine of patients with drug poisoning are most often performed to identify the ingested substances. Semiquantitative screening tests are usually sufficient for this purpose, while serum drug level determinations for therapeutic monitoring require rapid, specific and precise laboratory techniques. Results should be interpreted in the light of various pharmacokinetic factors and especially the presence of active metabolites, which may influence the concentration-effect relationships. Critical concentration ranges are known for several drugs but, except in cases with paracetamol overdose, drug levels alone are rarely decisive for the therapeutic procedure. Further studies are necessary to define the potential benefit of routine serum level measurements in drug poisoning.