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Utility of clozapine trough level reporting in clinical practice: A four-year retrospective evaluation from India
Amol N Patil1, Pankaj Khatri2, Sunil Sharma1
1Department of Pharmacology, PGIMER, Chandigarh, India.
Background:
Clozapine therapeutic drug monitoring (TDM) supports individualized dosing in treatment-resistant schizophrenia.
Aim:
This study evaluated the time trend of TDM reporting in routine practice.
Methods:
A retrospective audit of 100 consecutive clozapine TDM reports over 4 years was performed. Service utilization was assessed. Associations between daily dose, trough concentration, concentration-dose (C/D) ratio, therapeutic impressions (low, matching the dose, high, very high clozapine concentrations), and clinical advice accordingly were analyzed statistically.
Results:
The mean turnaround time was 20.9 ± 12 days, with a stable quarterly demand (~6 requests/quarter) for clozapine TDM. Dose correlated significantly with trough concentration (ρ = 0.453, P < 0.001). Forty-seven percent of concentrations were subtherapeutic. C/D ratio differed significantly between therapeutic impressions (β = 13.12, P < 0.001). Therapeutic impressions significantly influenced clinical advice (χ² = 54.03, P < 0.001). Nonadherence was identified in 8% of cases.
Conclusions:
Pharmacology TDM service utilization for clozapine was steady and continuing in treatment-resistant schizophrenia patient care.
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