Validation of direct method to quantify dexamethasone in human aqueous humor by LC–MS/MS

Aim: Dexamethasone (Dex) has been used for the treatment of ocular diseases, presenting concentrations up to 150 ng/ml in the biological matrix. Drug sampling has been performed from aqueous humor (AH), which the volume varies from 50 to 200 μl, becoming a challenge for analytical analyses. Results: We developed and validated a direct and sensitive method by LC–MS/MS for Dex measurement in human AH, using water as surrogate matrix to reduce the sample volume applied in some validation assays. With accuracies of 99.6% and precision within 15% in the range of 0.1–150 ng/ml, Dex had an 87-day stability. Conclusion: Our method is robust and sensitive enough to be applied in bioequivalence studies with human AH using only 20 μl of biological sample.