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Kim HY, Ruiter E, Jongedijk EM, Ak HK, Marais BJ, Pk B, Sawleshwarkar S, Touw DJ, Alffenaar JW. Saliva-based linezolid monitoring on a mobile UV spectrophotometer. J Antimicrob Chemother 2021; 76:1786-1792. [PMID: 33734351 DOI: 10.1093/jac/dkab075] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 02/15/2021] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND In TB, therapeutic drug monitoring (TDM) is recommended for linezolid; however, implementation is challenging in endemic settings. Non-invasive saliva sampling using a mobile assay would increase the feasibility of TDM. OBJECTIVES To validate a linezolid saliva assay using a mobile UV spectrophotometer. METHODS The saliva assay was developed using NanoPhotometer NP80® and linezolid concentrations were quantified using second-order derivative spectroscopy. Sample preparation involved liquid-liquid extraction of saliva, using saturated sodium chloride and ethyl acetate at 1:1:3 (v/v/v). The assay was validated for accuracy, precision, selectivity, specificity, carry-over, matrix effect, stability and filters. Acceptance criteria were bias and coefficient of variation (CV) <15% for quality control (QC) samples and <20% for the lower limit of quantification (LLOQ). RESULTS Linezolid concentrations correlated with the amplitude between 250 and 270 nm on the second-order derivative spectra. The linezolid calibration curve was linear over the range of 3.0 to 25 mg/L (R2 = 0.99) and the LLOQ was 3.0 mg/L. Accuracy and precision were demonstrated with bias of -7.5% to 2.7% and CV ≤5.6%. The assay met the criteria for selectivity, matrix effect, carry-over, stability (tested up to 3 days) and use of filters (0.22 μM Millex®-GV and Millex®-GP). Specificity was tested with potential co-medications. Interferences from pyrazinamide, levofloxacin, moxifloxacin, rifampicin, abacavir, acetaminophen and trimethoprim were noted; however, with minimal clinical implications on linezolid dosing. CONCLUSIONS We validated a UV spectrophotometric assay using non-invasive saliva sampling for linezolid. The next step is to demonstrate clinical feasibility and value to facilitate programmatic implementation of TDM.
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Affiliation(s)
- Hannah Yejin Kim
- Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, Camperdown, NSW, Australia.,Westmead Hospital, Westmead, NSW, Australia.,Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney, Camperdown, NSW, Australia
| | - Evelien Ruiter
- Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, Camperdown, NSW, Australia.,School of Pharmacy, Utrecht University, Utrecht, The Netherlands
| | - Erwin M Jongedijk
- University of Groningen, University Medical Center Groningen, Department of Clinical Pharmacy and Pharmacology, Groningen, The Netherlands
| | | | - Ben J Marais
- Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney, Camperdown, NSW, Australia.,Department of Infectious Diseases and Microbiology, The Children's Hospital at Westmead, Westmead, Australia
| | - Bhavani Pk
- National Institute for Research in Tuberculosis, Chennai, India
| | - Shailendra Sawleshwarkar
- Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney, Camperdown, NSW, Australia.,Westmead Clinical School, Faculty of Medicine and Health, The University of Sydney, Westmead, NSW, Australia
| | - Daan J Touw
- University of Groningen, University Medical Center Groningen, Department of Clinical Pharmacy and Pharmacology, Groningen, The Netherlands
| | - Jan-Willem Alffenaar
- Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, Camperdown, NSW, Australia.,Westmead Hospital, Westmead, NSW, Australia.,Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney, Camperdown, NSW, Australia
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