Purpose Since glomerular filtration rate (GFR) is responsible for the elimination of a large number of water-soluble drugs, the aim of this study was to develop a semi-physiological function for GFR maturation from neonates to adults. Methods In the pharmacokinetic analysis (NONMEM VI) based on data of gentamicin, tobramycin and vancomycin collected in 1,760 patients (age 1 day–18 years, bodyweight 415 g–85 kg), a distinction was made between drug-specific and system-specific information. Since the maturational model for clearance is considered to contain system-specific information on the developmental changes in GFR, one GFR maturational function was derived for all three drugs. Results Simultaneous analysis of these three drugs showed that maturation of GFR mediated clearance from preterm neonates to adults was best described by a bodyweight-dependent exponent (BDE) function with an exponent varying from 1.4 in neonates to 1.0 in adults (ClGFR = Cldrug*(BW/4 kg)BDE with BDE = 2.23*BW−0.065). Population clearance values (Cldrug) for gentamicin, tobramycin and vancomycin were 0.21, 0.28 and 0.39 L/h for a full term neonate of 4 kg, respectively. Discussion Based on an integrated analysis of gentamicin, tobramycin and vancomycin, a semi-physiological function for GFR mediated clearance was derived that can potentially be used to establish evidence based dosing regimens of renally excreted drugs in children.

AimsExtracorporeal membrane oxygenation (ECMO) is a life support system used during severe respiratory or cardiorespiratory failure. The objective of this study was to characterize the population pharmacokinetics of vancomycin during ECMO. MethodsA population model was developed using WinNonMix (Version 2.0.1) from a total of 366 plasma observations in 45 patients, including term neonates, older children and adults. The study utilized both rich prospective and sparse retrospective data. Prospective samples were drawn at baseline and then 30, 60,90, 120, 180, 240, 300, 360 and 420 min postinfusion. Steady state concentrations were obtained retrospectively from an assay database, cross-referencing with the patients' medical records. ResultsData were examined using a two-compartment model with an additive and proportional residual error. Model fit improved substantially when clearance, CL (l kg -1 h -1 ) was modelled as a nonlinear function of serum creatinine (Cr) m mol l -1 . There was a linear relationship between CL and age up to 1000 days: CL (Age < 1000 days) = [2.4 + 0.0018 ¥ Age (days)]/Cr; CL (Age > 1000 days) = 4.3/Cr. Age also influenced central volume ( V 1) when included in the model as a dichotomous variable: V 1 (Age < 4000 days) = 0.45 l kg -1 ; V 1 (Age > 4000 days) = 0.36 l kg -1 . Intercompartmental clearance and tissue volume were estimated to be 0.09 l kg -1 h -1 and 0.25 l kg -1 , respectively. Model validation in a separate group of 20 patients revealed a bias of -7.7% and a precision of 26.7%. ConclusionsThe clearance of vancomycin was decreased and its volume of distribution increased in patients receiving ECMO, suggesting altered drug disposition during this treatment.

Sedative agents are routinely administered to critically ill patients, both on and off extracorporeal membrane oxygenation (ECMO), to enable patients to be comfortable and facilitate patient management. It has been observed empirically in our paediatric intensive care unit that doses of sedative drugs required to achieve desired levels of sedation in ECMO patients are far greater than those used in non-ECMO patients. These differences could not simply be accounted for by differences in patient types, clinical status or sedation levels. We therefore undertook an in vitro evaluation of drug binding in ECMO circuits. This study investigated how the polyvinyl chloride (PVC) and silicone rubber components of neonatal ECMO circuits affect drug delivery in patients through drug sorption. Phase 1 investigated drug uptake by the two polymers in static solutions of known concentrations of four commonly used sedative drugs: lorazepam, midazolam, diazepam and propofol. Phase 2 involved the setting up of a complete neonatal ECMO circuit, injecting the drug solutions pre reservoir at a flow rate of 350 ml/min and collecting samples post-oxygenator for analysis. Phase 1 results revealed significant uptake of drugs with losses in the range 40-98% and in the order propofol > diazepam > midazolam > orazepam. Phase 2 results were similar and in the first 40 min of running an ECMO circuit only 10% of propofol passed through the circuit. These results may help to explain observed clinical phenomena and raise important issues regarding drug dosing in ECMO patients.

BackgroundAntibiotic dosing in neonates varies between countries and centres, suggesting suboptimal exposures for some neonates. We aimed to describe variations and factors influencing the variability in the dosing of frequently used antibiotics in European NICUs to help define strategies for improvement.MethodsA sub-analysis of the European Study of Neonatal Exposure to Excipients point prevalence study was undertaken. Demographic data of neonates receiving any antibiotic on the study day within one of three two-week periods from January to June 2012, the dose, dosing interval and route of administration of each prescription were recorded. The British National Formulary for Children (BNFC) and Neofax were used as reference sources. Risk factors for deviations exceeding ±25% of the relevant BNFC dosage recommendation were identified by multivariate logistic regression analysis.ResultsIn 89 NICUs from 21 countries, 586 antibiotic prescriptions for 342 infants were reported. The twelve most frequently used antibiotics – gentamicin, penicillin G, ampicillin, vancomycin, amikacin, cefotaxime, ceftazidime, meropenem, amoxicillin, metronidazole, teicoplanin and flucloxacillin – covered 92% of systemic prescriptions. Glycopeptide class, GA <32 weeks, 5th minute Apgar score <5 and geographical region were associated with deviation from the BNFC dosage recommendation. While the doses of penicillins exceeded recommendations, antibiotics with safety concerns followed (gentamicin) or were dosed below (vancomycin) recommendations.ConclusionsThe current lack of compliance with existing dosing recommendations for neonates needs to be overcome through the conduct of well-designed clinical trials with a limited number of antibiotics to define pharmacokinetics/pharmacodynamics, efficacy and safety in this population and by efficient dissemination of the results.Electronic supplementary materialThe online version of this article (doi:10.1186/s12887-015-0359-y) contains supplementary material, which is available to authorized users.