Abstract

Background: As the pharmacokinetics of methadone exhibit large inter-subject variability, providing a simple and reliable analytical method for the monitoring of methadone levels in biological samples during methadone maintenance therapy is necessary in order to determine an appropriate maintenance dosage.

Method: Determination of methadone in exhaled breath condensate (EBC) is performed using capillary electrophoresis in stacking mode. EBC is obtained using a simple cooling lab-made system.

Results: The simplicity of the EBC matrix renders the sample analyzable without any pretreatment step. The LLOQ is 0.3 µg/mL across a linear range of 0.3–5 µg/mL. The developed method was validated according to US FDA guidelines and successfully applied for the determination of methadone levels in four patients undergoing methadone maintenance therapy.

Conclusion: A simple and fast method was presented for determination of methadone in EBC with minimum required sample volume.

Keywords: Exhaled breath condensate, methadone, capillary electrophoresis, methadone maintenance therapy, field-amplified sample injection, direct injection.

Graphical Abstract