Safety of Metronidazole in Late Pre-term and Term Infants with Complicated Intra-abdominal Infections

Age-Dependent Abundance of CYP450 Enzymes Involved in Metronidazole Metabolism: Application to Pediatric PBPK Modeling

The expression of cytochrome P450 (CYP) enzymes is highly variable and associated with factors, such as age, genotype, sex, and disease states. In this study, quantification of metronidazole metabolizing CYP isoforms (CYP2A6, CYP2E1, CYP3A4, CYP3A5, and CYP3A7) in human liver microsomes from 115 children and 35 adults was performed using a quantitative proteomics method. The data confirmed age-dependent increase in CYP2A6, CYP2E1, and CYP3A4 abundance, whereas, as expected, CYP3A7 abundance showed postnatal decrease with age. In particular, the fold difference (neonatal to adulthood levels) in the protein abundance of CYP2A6, CYP2E1, and CYP3A4 was 14, 11, and 20, respectively. In contrast, protein abundance of CYP3A7 was > 125-fold higher in the liver microsomes of neonates than of adults. The abundance of CYP2A6 and CYP3A5 was associated with genotypes, rs4803381 and rs776746, respectively. A proteomics-informed physiologically based pharmacokinetic (PBPK) model was developed to describe the pharmacokinetics of metronidazole and its primary metabolite, 2-hydroxymethylmetronidazole. The model revealed an increase in the metabolite-to-parent ratio with age and showed a strong correlation between CYP2A6 abundance and metabolite formation (r2 = 0.75). Notably, the estimated contribution of CYP3A7 was ~ 75% in metronidazole clearance in neonates. These data suggest that variability in CYP2A6 and CYP3A7 in younger children poses the risk of variable pharmacokinetics of metronidazole and its active metabolite with a potential impact on drug efficacy and safety. No sex-dependent difference was observed in the protein abundance of the studied CYPs. The successful integration of hepatic CYP ontogeny data derived from a large liver bank into the pediatric PBPK model of metronidazole can be extended to other drugs metabolized by the studied CYPs.

Opportunistic dried blood spot sampling validates and optimizes a pediatric population pharmacokinetic model of metronidazole

Pharmacokinetic models rarely undergo external validation in vulnerable populations such as critically ill infants, thereby limiting the accuracy, efficacy, and safety of model-informed dosing in real-world settings. Here, we describe an opportunistic approach using dried blood spots (DBS) to evaluate a population pharmacokinetic model of metronidazole in critically ill preterm infants of gestational age (GA) ≤31 weeks from the Metronidazole Pharmacokinetics in Premature Infants (PTN_METRO, NCT01222585) study. First, we used linear correlation to compare 42 paired DBS and plasma metronidazole concentrations from 21 preterm infants [mean (SD): post natal age 28.0 (21.7) days, GA 26.3 (2.4) weeks]. Using the resulting predictive equation, we estimated plasma metronidazole concentrations (ePlasma) from 399 DBS collected from 122 preterm and term infants [mean (SD): post natal age 16.7 (15.8) days, GA 31.4 (5.1) weeks] from the Antibiotic Safety in Infants with Complicated Intra-Abdominal Infections (SCAMP, NCT01994993) trial. When evaluating the PTN_METRO model using ePlasma from the SCAMP trial, we found that the model generally predicted ePlasma well in preterm infants with GA ≤31 weeks. When including ePlasma from term and preterm infants with GA >31 weeks, the model was optimized using a sigmoidal Emax maturation function of postmenstrual age on clearance and estimated the exponent of weight on volume of distribution. The optimized model supports existing dosing guidelines and adds new data to support a 6-hour dosing interval for infants with postmenstrual age >40 weeks. Using an opportunistic DBS to externally validate and optimize a metronidazole population pharmacokinetic model was feasible and useful in this vulnerable population.

A Validated UHPLC-MS/MS Method to Quantify Eight Antibiotics in Quantitative Dried Blood Spots in Support of Pharmacokinetic Studies in Neonates

OBJECTIVES

Conduction of pharmacokinetic (PK) study in pediatric patients is challenging due to blood sampling limits. The dried blood spots (DBS) method represents a potential matrix for microsampling in support of PK studies in children. Herein, we used the Capitainer^® qDBS device to develop a DBS method that can collect an exact 10 µL volume of blood on a paper card. This DBS method was developed to simultaneously quantify the concentrations of eight antibiotics, including sulbactam, tazobactam, ampicillin, meropenem, cefotaxime, cefoperazone, piperacillin, and metronidazole using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS).

METHODS

The prepared DBS samples were extracted in methanol containing acetaminophen as the internal standard at 20 °C on a block bath shaker at 500 rpm for 30 min. The extracted antibiotics were eluted on an Acquity UPLC HSS T3 column (2.1 × 50 mm, 1.8 µm) using gradient elution with a total chromatographic run time of 6.5 min. The precursor and product ions of the analytes were detected by use of the multiple reaction monitoring (MRM) mode.

RESULTS

No interfering peaks at the respective retention times of the analytes were observed in DBS samples. The lower limits of quantification (LLOQ) for the antibiotics were between 0.25 and 2.0 μg/mL, and satisfactory accuracies (intra/inter-assay bias -16.7 to +13.6%) and precisions (intra/inter-assay coefficient of variations 1.5-15.6%) were obtained for the analytes. As a proof of concept, the method was applied to DBS samples obtained from neonatal patients treated with ampicillin and piperacillin/sulbactam.

CONCLUSIONS

The DBS method is simple and robust, and it can be used in children with limited blood sampling.

Exposure-response Relationships of Metronidazole in Infants: Integration of Electronic Health Record Data With Population Pharmacokinetic Modeling-derived Exposure Simulation

BACKGROUND

Infants frequently receive metronidazole at variable doses and duration for surgical site infection prophylaxis and treatment of intra-abdominal infections. Seizures are a rare (but potentially devastating) side effect of metronidazole, yet the prevalence of seizures in infants, as well as the relationship with metronidazole dose and exposure, are unknown.

METHODS

We examined the Pediatrix Clinical Data Warehouse for infants in neonatal intensive care units from 1997 to 2018 who received at least 1 dose of metronidazole during their first 120 days of life. We used an existing population pharmacokinetic model to simulate exposure parameters, estimating multivariable associations between metronidazole dosing and exposure parameters, and the occurrence of seizure.

RESULTS

There were 19,367 intravenous doses of metronidazole given to 1546 infants, and 31 experienced a seizure. Infants with a seizure had a longer median (interquartile values) duration of metronidazole exposure than those without (11 days [6, 15] vs. 7 [4, 11], P = 0.01). Each added day of metronidazole (OR = 1.06, 95% CI: 1.02-1.10), and each standard deviation increase in cumulative area under the plasma concentration-time curve (OR = 1.27, 95% CI: 1.11-1.45) were associated with increased odds of seizure. Higher simulated maximum plasma concentration was associated with lower odds of seizure (OR = 0.88, 95% CI: 0.81-0.96).

CONCLUSIONS

Longer metronidazole exposure and higher cumulative exposure could be associated with increased odds of infant seizures. Using a large observational dataset allowed us to identify a rare adverse event, but prospective studies are needed to validate this finding and further characterize metronidazole dose- and exposure-safety relationships.

Association between neonatal intensive care unit medication safety practices, adverse events, and death

OBJECTIVE

Determine the associations between neonatal intensive care unit (NICU) medication safety practices, laboratory-based adverse events (lab-AEs), and death.

STUDY DESIGN

We combined data from a 2016 survey of Pediatrix NICUs on use of medication safety practices with 2014-2016 infant data. We grouped NICUs based on the number of safety practices used (≤5, 6-7, and 8-10) and evaluated the association between the number of safety practices used and lab-AEs and deaths using logistic regressions.

RESULTS

Of the 94 NICUs included, 17% used ≤5 medication safety practices, 51% used 6-7, and 32% used 8-10. NICUs with more safety practices did not have a difference in lab-AEs or death.

CONCLUSION

In this cohort, the use of more medication safety practices was not associated with fewer lab-AEs or decreased death.

Early Life Antibiotics Influence In Vivo and In Vitro Mouse Intestinal Epithelium Maturation and Functioning

BACKGROUND & AIMS

The use of antibiotics (ABs) is a common practice during the first months of life. ABs can perturb the intestinal microbiota, indirectly influencing the intestinal epithelial cells (IECs), but can also directly affect IECs independent of the microbiota. Previous studies have focused mostly on the impact of AB treatment during adulthood. However, the difference between the adult and neonatal intestine warrants careful investigation of AB effects in early life.

METHODS

Neonatal mice were treated with a combination of amoxicillin, vancomycin, and metronidazole from postnatal day 10 to 20. Intestinal permeability and whole-intestine gene and protein expression were analyzed. IECs were sorted by a fluorescence-activated cell sorter and their genome-wide gene expression was analyzed. Mouse fetal intestinal organoids were treated with the same AB combination and their gene and protein expression and metabolic capacity were determined.

RESULTS

We found that in vivo treatment of neonatal mice led to decreased intestinal permeability and a reduced number of specialized vacuolated cells, characteristic of the neonatal period and necessary for absorption of milk macromolecules. In addition, the expression of genes typically present in the neonatal intestinal epithelium was lower, whereas the adult gene expression signature was higher. Moreover, we found altered epithelial defense and transepithelial-sensing capacity. In vitro treatment of intestinal fetal organoids with AB showed that part of the consequences observed in vivo is a result of the direct action of the ABs on IECs. Lastly, ABs reduced the metabolic capacity of intestinal fetal organoids.

CONCLUSIONS

Our results show that early life AB treatment induces direct and indirect effects on IECs, influencing their maturation and functioning.