Relevance of Clinical Pharmacological Comments in TDM

Comments given by clinical pharmacologists to determinations of drug concentrations in TDM are accepted very controversially by clinicians. In particular in psychiatry clinicians often feel supervised or patronised by such comments. Pure laboratory data are often misinterpreted, because the „normal range“ given does not meet individual needs. We analyse approximately 200 specimens/month of clozapine and olanzapine. Our dosage related reference range is 0.5–1.0×10^–3l^–1 and 1.0–2.0×10^–3l^–1, respectively. Some 40% of our determinations reveal deviations from these reference values, even if the concentration itself is within the „normal range“ used in the laboratory, which holds true for about 80 of these 40%. Most often the values are „relatively low“ which may be attributed to the patients' smoking. Some 5% of the values are „relatively high“ which may be attributed to drug interactions such as 2D6-inhibition by metoprolol and timolol or that remain unexplained being suspect of poor metabolising. In particular young physicians estimate clinical pharmacological commenting whereas experienced clinical specialists feel they know their patients better than the clinical pharmacologist.