Saliva-based linezolid monitoring on a mobile UV spectrophotometer

Abstract Background In TB, therapeutic drug monitoring (TDM) is recommended for linezolid; however, implementation challenging in endemic settings. Non-invasive saliva sampling using a mobile assay would increase the feasibility of TDM. Objectives To validate linezolid UV spectrophotometer. Methods The was developed NanoPhotometer NP80® and concentrations were quantified second-order derivative spectroscopy. Sample preparation involved liquid–liquid extraction saliva, saturated sodium chloride ethyl acetate at 1:1:3 (v/v/v). validated accuracy, precision, selectivity, specificity, carry-over, matrix effect, stability filters. Acceptance criteria bias coefficient variation (CV) <15% quality control (QC) samples <20% lower limit quantification (LLOQ). Results Linezolid correlated with amplitude between 250 270 nm on spectra. calibration curve linear over range 3.0 to 25 mg/L (R2 = 0.99) LLOQ mg/L. Accuracy precision demonstrated ?7.5% 2.7% CV ?5.6%. met (tested up 3 days) use filters (0.22 ?M Millex®-GV Millex®-GP). Specificity tested potential co-medications. Interferences from pyrazinamide, levofloxacin, moxifloxacin, rifampicin, abacavir, acetaminophen trimethoprim noted; minimal clinical implications dosing. Conclusions We spectrophotometric non-invasive linezolid. next step demonstrate value facilitate programmatic