Development and Validation of a Free Carbamazepine Assay on an Automated Chemistry Analyzer

Abstract

Background Carbamazepine is an effective drug for treating seizures and trigeminal neuralgia. Therapeutic drug monitoring of free carbamazepine in serum can be useful in situations that drug--protein binding is altered to guide regimen adjustment and to aid in the diagnosis of clinical toxicity. Methods Separation of the nonprotein bound carbamazepine was achieved via ultrafiltration through a molecular weight cut-off filter. A method for free carbamazepine measurement was developed on the automated cobas chemistry analyzers (Roche Diagnostics) by modifying the Carbamazepine Gen 4 assay (Roche Diagnostics). Assay performance characteristics were established including precision, accuracy, reportable range, analytical specificity, and stability. Results The intra- and inter-assay imprecision was 0%-1.4% and 2.4%-5.1%, respectively. The lower limit of quantitation was 0.3 µg/mL, and the assay was linear up to 10.0 µg/mL. A spike recovery study, using reference standard material, showed recovery was 93.5%--101.3% across the analytical measurement range. Method comparison with a reference laboratory method demonstrated equivalent performance with a slope of 1.01, intercept of 0.09, and correlation coefficient of 0.9948. Conclusion This assay provides a simple and accurate method for monitoring free carbamazepine with a fast turnaround time.

Pharmaceutical and Clinical Assessment of Multi-source Tegretol Sold in Egypt

“…The CBZ plasma test was done using CBZ ELISA Plate kit, Eurofins Abraxis, Warminster, USA in the laboratory of the Medical Research Institute, Alexandria University. 43 The sodium plasma level test was done in the laboratory of the Main Alexandria University Hospital, Alexandria University.…”