Therapeutic drug monitoring of nevirapine in saliva in Uganda using high performance liquid chromatography and a low cost thin-layer chromatography technique.

Mohammed Lamorde,Lillian Nakatudde-Katumba,David Burger,Kim Sigaloff,Quirine Fillekes,Allan Buzibye,Joshua Kayiwa,Cissy Kityo,Tobias F Rinke De Wit,Concepta Merry

doi:10.1186/1471-2334-14-473

Abstract

BackgroundIn resource limited settings access to laboratory monitoring of HIV treatment is limited and therapeutic drug monitoring is generally unavailable. This study aimed to evaluate nevirapine concentrations in saliva using low-cost thin-layer chromatography (TLC) and nevirapine concentrations in plasma and saliva using high performance liquid chromatography (HPLC) methods; and to correlate nevirapine plasma concentrations to HIV treatment outcomes in Ugandan patients.MethodsPaired plasma and stimulated saliva samples were obtained from Ugandan, HIV-infected adults on nevirapine-based ART. Nevirapine concentrations were measured using a validated HPLC method and a novel TLC method. Plasma nevirapine concentrations <3.0 mg/L using HPLC were considered subtherapeutic. Negative/positive predictive values of different thresholds for subtherapeutic nevirapine concentrations in saliva were determined. Virologic testing and, if applicable, HIV drug resistance testing was performed.ResultsMedian (interquartile range, IQR) age of 297 patients was 39.1 (32.8-45.2) years. Three hundred saliva and 287 plasma samples were available for analysis. Attempts failed to determine nevirapine saliva concentrations by TLC. Using HPLC, median (IQR) nevirapine concentrations in saliva and plasma were 3.40 (2.59-4.47) mg/L and 6.17 (4.79-7.96) mg/L, respectively. The mean (coefficient of variation,%) nevirapine saliva/plasma ratio was 0.58 (62%). A cut-off value of 1.60 mg/L nevirapine in saliva was associated with a negative/positive predictive value of 0.99/0.72 and a sensitivity/specificity of 87%/98% for predicting subtherapeutic nevirapine plasma concentrations, respectively. Only 5% (15/287) of patients had subtherapeutic nevirapine plasma concentrations, of which 3 patients had viral load results > 400 copies/mL. Patients with nevirapine concentrations in plasma <3.0 mg/L had an Odds Ratio of 3.29 (95% CI: 1.00 – 10.74) for virological failure (viral load >400 copies/mL).ConclusionsThe low-cost TLC technique for monitoring nevirapine in saliva was unsuccessful but monitoring nevirapine saliva and plasma concentrations using HPLC was shown to be feasible in the research/specialist context in Uganda. Further optimization and validation is required for the low-cost TLC technique.

Highlights

In resource limited settings access to laboratory monitoring of HIV treatment is limited and therapeutic drug monitoring is generally unavailable
A total of 297 patients were enrolled in the study: 120 (40.4%) were co-enrolled from the Pan African Studies to Evaluate Resistance (PASER)-M cohort and the remaining 177 (59.6%) were enrolled from antiretroviral clinics in the three study sites
We found a strong positive correlation between nevirapine concentrations in plasma and saliva (Spearman’s rho, 0.886, p

Summary

Introduction

In resource limited settings access to laboratory monitoring of HIV treatment is limited and therapeutic drug monitoring is generally unavailable. Access to antiretroviral therapy (ART) is improving in developing countries which experience the greatest disease burden arising from HIV infection. Laboratory monitoring of ART efficacy is often limited to the CD4 cell count - a test that has low accuracy for identifying patients experiencing treatment failure to ART [3]. Low-cost laboratory tests are needed to optimize ART monitoring in developing countries. Nevirapine, a non-nucleoside reverse transcriptase inhibitor, is one of the most widely used components of first-line ART, because of its low cost, good long-term tolerability, and high efficacy [4,5]. For therapeutic drug monitoring (TDM) of nevirapine a trough plasma concentration >3.0 mg/L is suggested [8,9]. Nevirapine pharmacokinetics exhibit marked interpatient variability that can be explained in part by genetic differences, drug-drug interactions, pregnancy and other (ethnic) factors [10,11,12]

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