Development, validation and clinical application of a method for the simultaneous quantification of lamivudine, emtricitabine and tenofovir in dried blood and dried breast milk spots using LC-MS/MS

Objectives: To present the validation and clinical application of a LC-MS/MS method for the quantification of lamivudine (3TC), emtricitabine (FTC) and tenofovir (TFV) in dried blood spots (DBS) and dried breast milk spots (DBMS). Methods: DBS and DBMS were prepared from 50 and 30 mu L of drug-spiked whole blood and human breast milk, respectively. Following extraction with acetonitrile and water, chromatographic separation utilised a Synergi polar column with a gradient mobile phase program consisting of 0.1% formic acid in water and 0.1% formic acid in acetonitrile. Detection and quantification was performed using a TSQ Quantum Ultra triple quadrupole mass spectrometer. The analytical method was used to evaluate NRTI drug levels in HIV-positive nursing mothers-infant pairs. Results: The assay was validated over the concentration range of 16.6-5000 ng/mL for 3TC, FTC and TFV in DBS and DBMS except for TFV in DBMS where linearity was established from 4.2-1250 ng/mL. Intra and inter-day precision (%CV) ranged from 3.5-8.7 and accuracy was within 15% for all analytes in both matrices. The mean recovery in DBS was > 61% and in DBMS > 43% for all three analytes. Matrix effect was insignificant. Median AUC(0.8) values in maternal DBS and DBMS, respectively, were 4683 (4165-6057) and 6050 (5217-6417) ng h/mL for 3TC, 3312 (2259-4312) and 4853 (4124-6691) ng h/mL for FTC and 1559 (930-1915) and 56 (45-80) ng h/mL for TFV. 3TC and FTC were quantifiable (> 16.6 ng/mL) in DBS from 2/6 and 1/6 infants respectively whereas TFV was undetectable in all infants. Conclusions: DBS and DBMS sampling for bioanalysis of 3TC, FTC and TFV is straightforward, robust, accurate and precise, and ideal for use in low-resource settings.