Comparative Analysis of Ampicillin Plasma and Dried Blood Spot Pharmacokinetics in Neonates

Ampicillin Pharmacokinetics in Peripartum and Laboring Women

OBJECTIVE

 Ampicillin is used for multiple peripartum indications including prevention of neonatal group B streptococcus (GBS) and treatment of chorioamnionitis. Despite its widespread use in obstetrics, existing pharmacokinetic data for ampicillin do not address contemporary indications or dosing paradigms for this population. We sought to characterize the pharmacokinetic profile of ampicillin administered to laboring women.

STUDY DESIGN

 Using whole blood dried blood spot sampling technique, maternal blood samples were collected at specified times from 31 women receiving intravenous (IV) ampicillin for peripartum indications. Women received either a 2-g loading dose with 1-g administered every 4 hours (GBS) or 2-g every 6 hours (chorioamnionitis). Pharmacokinetics were analyzed via a population approach with nonlinear mixed-effect modeling.

RESULTS

 The data were best described by a two-compartment model with first-order elimination, with the following whole blood parameters: central volume of distribution (V1), 75.2 L (95% confidence interval [CI]: 56.3-93.6); clearance (CL), 82.4 L/h (95% CI: 59.7-95.7); intercompartmental clearance (Q), 20.9 L/h (95% CI: 16.2-38.2); and peripheral volume of distribution (V2), 61.1 L (95% CI: 26.1-310.5). Interpatient variation in CL and V1 was large (42.0 and 56.7%, respectively). Simulations of standard dosing strategies demonstrated over 98% of women are predicted to achieve an estimated free plasma concentration above mean inhibitory concentration (MIC) of 0.5 μg/mL for more than 50% of the dosing interval.

CONCLUSION

 Although large variation in the pharmacokinetics of ampicillin in pregnant women exists, as predicted by our model, current standard dosing strategies achieve adequate exposure for GBS in nearly all patients.

KEY POINTS

· IV ampicillin is widely used in obstetrics.. · Pharmacokinetic studies are lacking.. · Ampicillin pharmacokinetics were established.. · Ampicillin clearance and volume of distribution are high.. · Current ampicillin dosing strategies are sufficient..

Dried Blood Spots-A Platform for Therapeutic Drug Monitoring (TDM) and Drug/Disease Response Monitoring (DRM)

This review provides an overview on the current applications of dried blood spots (DBS) as matrices for therapeutic drug (TDM) and drug or disease response monitoring (DRM). Compared with conventional methods using plasma/serum, DBS offers several advantages, including minimally invasiveness, a small blood volume requirement, reduced biohazardous risk, and improved sample stability. Numerous assays utilising DBS for TDM have been reported in the literature over the past decade, covering a wide range of therapeutic drugs. Several factors can affect the accuracy and reliability of the DBS sampling method, including haematocrit (HCT), blood volume, sampling paper and chromatographic effects. It is crucial to evaluate the correlation between DBS concentrations and conventional plasma/serum concentrations, as the latter has traditionally been used for clinical decision. The feasibility of using DBS sampling method as an option for home-based TDM is also discussed. Furthermore, DBS has also been used as a matrix for monitoring the drug or disease responses (DRM) through various approaches such as genotyping, viral load measurement, assessment of inflammatory factors, and more recently, metabolic profiling. Although this research is still in the development stage, advancements in technology are expected to lead to the identification of surrogate biomarkers for drug treatment in DBS and a better understanding of the correlation between DBS drug levels and drug responses. This will make DBS a valuable matrix for TDM and DRM, facilitating the achievement of pharmacokinetic and pharmacodynamic correlations and enabling personalised therapy.

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.

Use of Antibiotics in Preterm Newborns

Due to complex maturational and physiological changes that characterize neonates and affect their response to pharmacological treatments, neonatal pharmacology is different from children and adults and deserves particular attention. Although preterms are usually considered part of the neonatal population, they have physiological and pharmacological hallmarks different from full-terms and, therefore, need specific considerations. Antibiotics are widely used among preterms. In fact, during their stay in neonatal intensive care units (NICUs), invasive procedures, including central catheters for parental nutrition and ventilators for respiratory support, are often sources of microbes and require antimicrobial treatments. Unfortunately, the majority of drugs administered to neonates are off-label due to the lack of clinical studies conducted on this special population. In fact, physiological and ethical concerns represent a huge limit in performing pharmacokinetic (PK) studies on these subjects, since they limit the number and volume of blood sampling. Therapeutic drug monitoring (TDM) is a useful tool that allows dose adjustments aiming to fit plasma concentrations within the therapeutic range and to reach specific drug target attainment. In this review of the last ten years’ literature, we performed Pubmed research aiming to summarize the PK aspects for the most used antibiotics in preterms.

Infection control and other stewardship strategies in late onset sepsis, necrotizing enterocolitis, and localized infection in the neonatal intensive care unit

Suspected or proven late onset sepsis, necrotizing enterocolitis, urinary tract infections, and ventilator associated pneumonia occurring after the first postnatal days contribute significantly to the total antibiotic exposures in neonatal intensive care units. The variability in definitions and diagnostic criteria in these conditions lead to unnecessary antibiotic use. The length of treatment and choice of antimicrobial agents for presumed and proven episodes also vary among centers due to a lack of supportive evidence and guidelines. Implementation of robust antibiotic stewardship programs can encourage compliance with appropriate dosages and narrow-spectrum regimens.

Therapeutic drug monitoring of tacrolimus and mycophenolic acid in outpatient renal transplant recipients using a volumetric dried blood spot sampling device

AIMS

Tacrolimus and mycophenolic acid dosing after renal transplantation is individualized through therapeutic drug monitoring (TDM). Home-based dried blood spot (DBS) sampling has the potential to replace conventional TDM sampling at the clinic. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay was developed to quantify tacrolimus and mycophenolic acid in DBS and clinically validated for abbreviated area under the concentration-time curve (AUC) monitoring using an innovative volumetric DBS sampling device.

METHODS

Clinical validation was performed by direct comparison of paired DBS and whole blood (WB) (tacrolimus) and plasma (mycophenolic acid) concentrations and AUCs. Agreement was evaluated using Passing-Bablok regression, Bland-Altman analysis and DBS-to-WB predictive performance. TDM dosing recommendations based on both methods were compared to assess clinical impact.

RESULTS

Paired tacrolimus (n = 200) and mycophenolic acid (n = 192) DBS and WB samples were collected from 65 kidney(-pancreas) transplant recipients. Differences for tacrolimus and mycophenolic acid were within ±20% for 84.5% and 76.6% of concentrations and 90.5% and 90.7% of AUCs, respectively. Tacrolimus and mycophenolic acid dosing recommendation differences occurred on 44.4% and 4.7% of occasions. Tacrolimus DBS dosing recommendations were 0.35 ± 0.14 mg higher than for WB and 8 ± 3% of the initial dose. Mycophenolic acid DBS dosing recommendations were 23.3 ± 31.9 mg lower than for plasma and 2 ± 3.5% of the initial dose.

CONCLUSIONS

Tacrolimus and mycophenolic acid TDM for outpatient renal transplant recipients, based on abbreviated AUC collected with a DBS sampling device, is comparable to conventional TDM based on WB sampling. Patient training and guidance on good blood-spotting practices is essential to ensure method feasibility.