Determination of rilpivirine (TMC‐278) plasma concentrations by the conventional LC‐MS method

Background Rilpivirine (TMC‐278) is a second‐generation NNRTI that is highly potent against both wild‐type and drug‐resistant HIV‐1 strains. The quantification of rilpivirine in human plasma is important to support clinical studies and determine pharmacokinetic parameters of rilpivirine. Until now there has been a methodological report for the determination of rilpivirine using LC‐MS/MS. However, the MS‐MS detector needs to be delicately set and it is expensive. To bypass these difficulties, we aimed to develop more conventional procedures for determining rilpivirine plasma concentration by LC‐MS method. Methods A Waters Alliance 2695 HPLC and a Micromass ZQ‐2000 MS, controlled with MassLynx version 4.0 software, were used for detection. Our method involves rapid liquid‐liquid drug extraction from plasma and use of gradient elution on a reversed‐phase C18 column. The mobile phase comprised 0.1 mM EDTA in 0.1% acetic acid (65%), acetonitrile (15%), and methanol (20%). Quantitative analysis detected rilpivirine at m/z 367, and the internal standard, at m/z 313, all in the form of ions. Results The established LC‐MS method was validated by estimating the precision and accuracy for inter‐ and intraday analysis in the concentration range of 18–715 ng/ml. The calibration curve was linear in this range. Average accuracy ranged from 100.0 to 100.6%. Relative standard deviations of both inter‐ and intraday assays were less than 3.3%. Recovery of rilpivirine was more than 82.0%. Conclusions Our newly developed LC‐MS method achieves the same level of reproducibility and accuracy as the LC‐MS/MS method. Our method provides a conventional, accurate and precise way to determine rilpivirine in human plasma. This method can be used in routine clinical application for HIV‐1 infected patients, and permits management of drug interactions and toxicity for rilpivirine.