The Practice of TDM in an Austrian University Hospital Setting: What the Clinician Still has to be Reminded of ...

A recent prospective study performed in three mid-size psychiatric departments in Germany (Mueller et al. 2003, Pharmacopsychiatry 36: 98–104) has shown that TDM of antidepressants when used under routine clinical conditions improves the mental health of the patient and reduces the occurrence of adverse drug effects – but only if the psychiatrists ordering TDM does react appropriately to the reports from the TDM laboratory (Vuille et al. 1991, Pharmacopsychiatry 24: 190–195; Hiemke et al. 2003, Psychopharmakotherapie 10: 11–14). We compared these findings to our university hospital setting, analysing the 262 orders for a plasma level determination that our staff psychiatrists had issued in the year 2001. The total turnover for that year was 3,531 inpatients and 11,524 outpatients. Thus, our staff psychiatrists deemed it necessary to perform TDM in only 2% of the patients entrusted to them, suggesting that our clinicians greatly believe in their patients' compliance and pharmacokinetic conformity. For 227 of these 262 patients, a plasma level analysis was ordered only once, with 84% of these plasma levels being in the recommended range. In contrast, plasma levels for the remaining 35 patients, for whom more than one TDM during the course of treatment was judged necessary by our clinicians, only 46% of these 35 patients had plasma levels in the recommended range upon their first TDM (p=0.0002, Fisher's exact test, two-sided). Of the 27 inpatients of the 35 patients for whom TDM was ordered a second time, the median waiting time was 3 days. Actually, in as much as 38% of the cases TDM was ordered on same day the dose was changed by the clinician. In the 8 patients of the outpatient clinic for whom TDM was ordered more than once, TDM was never ordered 0–3 days after changing the dose, in 25% TDM was ordered 4–7 days after the dosing change, and in 75% it was ordered 8+ days after (p<0.0001 with respect to inpatient setting, chi square test). In 7 of the 35 patients who presented with plasma levels above the recommended range at the first TDM, the dose was not changed in 4 patients or even increased in 2 patients. Thus, with respect to the whole patient sample of 35, the proportion of such inappropriate dose adjustment to TDM was 17% (i.e., 6 of 35 adjustments), comparable to the German and the Swiss hospital staff psychiatrist sample.

Reference: Zernig et al. 2004, Therapeutic Drug Monitoring, in press