Determination of carbamazepine in fingerprints: a feasibility study to evaluate adherence in epilepsy patients.

Background: Fingerprint drug concentrations can be used as a noninvasive and convenient alternative to evaluate adherence to pharmacotherapy. Methods: Fingerprints were applied over glass slides, extracted and analyzed by ultra-high performance LC-MS/MS. The assay and drug adherence questionnaires were applied to 30 epilepsy patients. Results: The assay had linearity in the range 0.05-10 ng fingerprint -1 , with precision of 2.16-7.9% and accuracy of 95.0-102.8%. Carbamazepine (CBZ) levels in fingerprints were stable at 45°C for 15 days. Concentrations in patient samples were 0.06-9.28 ng fingerprint -1 . A significant difference (p = 0.003) was found between CBZ concentrations in fingerprints between patient groups divided as low and medium/high adherence. Conclusion: This method can potentially be applied to the identification of epilepsy patients with low adherence to CBZ pharmacotherapy.