Exploring The Use Of A Mobile Microvolume Spectrophotometer For Saliva-Based Monitoring Of Antiretroviral Drugs

Abstract

Introduction: Therapeutic drug monitoring can be used to evaluate the efficacy of HIV treatment and identify non-adherence. This study explored the possibility of an easy-to-use and non-invasive assay for monitoring antiretroviral drugs in saliva. Theoretical salivary concentrations from previous studies were 0.4 – 25.8 ng/ml for tenofovir, 15 – 718 ng/ml for lamivudine, and 3.125 – 100 ng/ml for efavirenz.

Methods: A mobile microvolume UV/visible light spectrophotometer operating at wavelengths of 200 – 900 nm was used. Drug-free saliva samples were obtained from six healthy volunteers and were spiked with antiretroviral drug.

Results: Calibration curves were made over a range of 2,500 – 50,000 ng/ml for tenofovir in ultrapure water (R² = 0.9994) at 261 nm, 200 – 800 ng/ml for lamivudine in saliva (R² = 0.7091) at 271 nm, and 1,500 – 4,000 ng/ml for efavirenz in saliva (R² = 0.9152) at 247 nm. The lowest limit of quantification (LLOQ) was determined to be 2,500 ng/ml for tenofovir, 200 ng/ml for lamivudine, and 2,000 ng/ml for efavirenz. The total absorbance of lamivudine and efavirenz in saliva exceeded the linear range for analysis.

Conclusions: The proposed spectrophotometer assay was not able to quantify tenofovir, lamivudine, and efavirenz in saliva. Further research with improved methods, different matrices or devices could be explored.