Qualitative determination of pregabalin in urine by spectrophotometric method

Abstract

Pregabalin is a gamma-amino-butyric acid analogue approved for the treatment of neuropathic pain, partial seizures, and generalized anxiety disorder. Pregabalin misuse and dependence has been increasing worldwide. Pregabalin assay on urine requires chromatography methods, which are not always available in developing countries’ laboratories. To address this, a UV/Visible spectrophotometry method to determine pregabalin in urine was optimized and validated for application in laboratories with limited resources. Analytical optimizations were conducted based on the reaction of Ninhydrin to amine functions of the pregabalin molecule. After urine deproteinization, ninhydrin was added to the deproteinized supernatant to form a coloured complex alongside the amine function. The European Medical Agency guidelines served as the main reference for analytical validation. The proposed method used UV/Visible spectrophotometry and chemical reagents, which are widely available in laboratories. This method showed good linearity in the range 100–500 μg.mL−1 (R2 = 0.9995), with no significant endogenous interference. The exogenous interference study was performed on 37 drugs and medicines; an interference with gabapentin was noted. The limit of detection was 50 μg.mL−1. The analysed samples could be stored for 3–7 days at +4 ̊C. Freezing (−20 ̊C) does not affect the results. The proposed method for determining pregabalin in urine samples is low-cost, simple, and fast, and it can therefore be used routinely as an alternative method when conventional methods are not available.