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A novel technique for collection of capillary blood, termed volumetric absorptive microsampling (VAMS), has been recently cleared by the FDA for collection of human blood. VAMS absorbs a fixed volume of blood (10 μl) and overcomes area bias and homogeneity issues associated with dried blood spot (DBS). This study is the application of VAMS for therapeutic drug monitoring (TDM) in human capillary blood. A liquid chromatography–tandem mass spectrometry (LC–MS/MS) workflow for analysis of VAMS sample was developed and validated. Concentration of hydroxychloroquine (HCQ) and its metabolites, desethylhydroxychloroquine (DHCQ), desethylchloroquine (DCQ), and bisdesethylchloroquine (BDCQ), in capillary blood on VAMS sampler were compared to those in venous blood in rheumatoid arthritis patients. Feasibility of capillary blood collected on both VAMS and DBS card were evaluated on patients. Stability of dried capillary blood on VAMS was also examined. Our results established that VAMS is a simple and accurate sampling technique that delivers the benefits of DBS sampling while overcoming the issues associated with hematocrit and homogeneity. It requires a small blood volume, simplifies sample logistics management, and may allow sample collection in the patient's home setting.VAMS was successfully applied for the first time to the therapeutic drug monitoring of HCQ in rheumatoid arthritis patients.LC–MS/MS workflow for analysis of VAMS sample was developed and validated.Drug concentrations of HCQ and its metabolites in capillary blood on VAMS device were compared to those in venous blood.Our results established that VAMS is simple, accurate and delivers the benefits of DBS while overcoming the issues of hematocrit and homogeneity.