Quality control and therapeutic drug monitoring

Dramatic improvements have been achieved in a relatively short time in the performance of therapeutic drug testing. The primary reasons for these advances have been the introduction of drug-specific immunoassays and, concomitantly, the availability of standards prepared in a biological matrix. For some drugs which are tested by other methods, such as the tricyclic antidepressants, interlaboratory variability is still excessively high. It is possible that this variability could be reduced through the proper preparation of serum-based standards. Manufacturers who provide quality control products could greatly assist the analyst by providing weighed-in target values for the drugs which have been added.