The treatment of poisoned patients is still largely defined by history, cli
nical assessment and interpretation of ancillary investigations. Measuremen
t of drug concentrations is clinically important for relatively few compoun
ds. Most measurements form an adjunct to and should not be considered a sub
stitute for clinical assessment. Drug concentrations are particularly impor
tant for those compounds where the concentration is predictive of serious t
oxicity in an otherwise asymptomatic patient.