Microsampling for monitoring gentamicin in neonates

Gentamicin is recommended as first-line treatment of neonatal sepsis. The use of gentamicin is associated with toxicity which complicates neonatal dosing and necessitates therapeutic drug monitoring (TDM). In a proof-of-concept investigation, we sought to compare (1) gentamicin concentrations obtained using volumetric absorptive microsampling (VAMS) to standard TDM plasma samples, and (2) the time taken to report results obtained using VAMS compared to standard TDM by the local hospital chemical pathology service. The difference between gentamicin concentrations obtained from plasma collected for routine clinical care and calculated plasma concentrations, based on samples collected in whole blood using VAMS, was −18.0% and −0.4% for two patients. The research laboratory reported results within the time taken for the routine chemical pathology laboratory to report results. This proof-of-concept study demonstrates that the use of microsampling for TDM by pathology services can fulfil the requirements of providing an accurate gentamicin concentration in a timely manner.