• Agnieszka Bienert, Alicja Bartkowska-Sniatkowska, Paweł Wiczling, Jowita Rosada-Kurasińska, Małgorzata Grześkowiak, Czesław Zaba, Artur Teżyk, Anna Sokołowska, Roman Kaliszan, and Edmund Grześkowiak.
• Department of Clinical Pharmacy and Biopharmacy, Karol Marcinkowski University of Medical Sciences, Marii Magdaleny 14, PL 61-861 Poznań, Poland. agnbienert@op.pl.
• Pharmacol Rep. 2013 Jan 1;65(1):107-21.

BackgroundThis study evaluates possible circadian rhythms during prolonged midazolam infusion in 27 pediatric intensive care unit (PICU) children under mechanical ventilation.MethodsBlood samples for midazolam and 1-OH-midazolam assay were collected throughout the infusion at different times of the day. The blood pressure, heart rate and body temperature were recorded every hour for the rhythms analysis. Population nonlinear mixed-effect modeling with NONMEM was used for data analysis.ResultsA two-compartment model for midazolam pharmacokinetics and a one-compartment model for midazolam metabolite adequately described the data. The 24 h profiles of all monitored physiological parameters were greatly disturbed/abolished in comparison with the well-known 24 h rhythmic patterns in healthy subjects. There was no significant circadian rhythm detected with respect to midazolam pharmacokinetics, its active metabolite pharmacokinetics and all monitored parameters.ConclusionsWe concluded that the light-dark cycle did not influence midazolam pharmacokinetics in intensive care units children. Also, endogenous rhythms in critically ill and sedated children are severely disturbed and desynchronized. Our results confirmed that it is necessary to adjust the dose of midazolam to the patient's body weight. The low value of midazolam clearances observed in our study was probably caused by mechanical ventilation, which was shown to decrease the cardiac output.

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