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BackgroundMidazolam is a first-line drug for treatment of status epilepticus,1 2 both by buccal and intravenous administration. In children with obesity, the midazolam pharmacokinetics may be altered, and the current dosing guidelines may therefore be insufficient.The aim of the study was to investigate the pharmacokinetics of midazolam, after intravenous administration, in obese and non-obese children, aged 11–18 years.MethodsTrial subjects were divided into groups by Body Mass Standard Deviation Score (SDS). All children received 1 µg midazolam administered an intravenous bolus dose. Thirteen blood samples were collected per participant at prespecified timepoints over 9 hours. Plasma concentration-time data was fitted to pharmacokinetic models using non-linear mixed effects modelling (NONMEM, 7.4).ResultsSeventy-two children were enrolled in the study, of these 67 children were included in the analysis. The pharmacokinetics of midazolam was best described with a two-compartment model. The changes in pharmacokinetics in children with obesity were best described with a linear function of BMI SDS on inter-compartmental clearance and peripheral volume. Thus, the rate of distribution was faster, and the peripheral volume of distribution was larger in children with obesity as compared to non-obese children. Simulations revealed that long-term infusions based on total body weight, could lead to high plasma concentrations in children with obesity. Furthermore, simulated plasma concentrations after a fixed buccal dose showed that children with obesity may be at risk of subtherapeutic plasma concentrations.ConclusionBMI SDS was shown to have a significant influence on the peripheral volume of distribution and the inter-compartmental clearance of midazolam. The current Danish dosing guidelines for status epilepticus (http://www.paediatri.dk), where midazolam dose is adjusted to total body weight or age, may lead to both supra- and subtherapeutic doses respectively, in children with obesity. However, confirmatory studies are needed.ReferencesSmith R, Brown J. Midazolam for status epilepticus. Aust Prescr. februar 2017;40(1):23–5.Ulvi H, Yoldas T, Müngen B, Yigiter R. Continuous infusion of midazolam in the treatment of refractory generalized convulsive status epilepticus. Neurol Sci Off J Ital Neurol Soc Ital Soc Clin Neurophysiol oktober 2002;23(4):177–82.Disclosure(s)Nothing to disclose