20 The relevance of TDM in opiate withdrawal

Introduction Levomethadone has a high interpatient variability in regards to the dose related serum concentration. It is unknown if the serum level correlates with withdrawal symptoms during opiate withdrawal.

Methods 31 patients (24 male, 7 female) were included in the study. The duration of opiate addiction was 15.2 ± 11.3 years. 17 patients were included in a levomethadone substitution program on admission. Levomethadone serum levels were measured during the off-tapering of levomethadone (after dose finding, days 2, 6 and 11 during the tapering off). The Subjective Opiate Withdrawal Scale (SOWS), the Objective Opiate Withdrawal Scale (OOWS) and Clinical Global Impression (CGI) were also measured at the same time points. ECG monitoring and monitoring for adverse drug reactions (UKU side effect rating scale) were also conducted.

Results A significant correlation was found for the dose of levomethadone to its serum level (r = 0.531; p = 0.001) and also for SOWS and OOWS to levomethadone serum levels (correlation coefficient −0.290; p = 0.011 and −0.280; p = 0.014 respectively). QtcB was elevated in two patients. For male patients QtcB 425.4 ± 19.2 ms, for female patients 437.5 ± 14.7 ms. The most common side effects were gastrointestinal side effects (n = 13), restlessness (n = 11), increased perspiration (n = 10) which could also be withdrawal effects. All serum levels of levomethadone were with 0–241 ng/ml below the therapeutic range of the AGNP guideline (250–400 ng/ml).

Conclusion The correlation of withdrawal symptoms with plasma levels of levomethadone makes TDM useful to optimize opiate withdrawal by avoiding severe withdrawal symptoms and discontinuation of the withdrawal.

Publication History

Article published online:
30 April 2020