Sample Preparation and Extraction in Small Sample Volumes Suitable for Pediatric Clinical Studies: Challenges, Advances, and Experiences of a Bioanalytical HPLC-MS/MS Method Validation Using Enalapril and Enalaprilat

A Self-Assembly Pipette Tip Restricted Access Mesoporous Polypyrrole Solid-Phase Extraction Coupled With Capillary Electrophoresis With Diode Array Detection for the Determination of Enalapril in Urine Samples

A miniaturized self-assembly pipette tip with restricted access mesoporous polypyrrole solid-phase extraction, combined with capillary electrophoresis with diode array detection (CE-DAD), was developed to rapidly extract and determine enalapril from urine samples. The CE-DAD technique used 50 mmol L-1 phosphate (pH 7) as the background electrolyte, a voltage of 13 kV, a 30 mbar hydrodynamic injection for 4 s, a capillary temperature of 25°C, and a wavelength of 195 nm to achieve a migration time of 6.3 min with satisfactory peak asymmetry and no interfering and/or baseline noise. The factors that influenced the extraction efficiency were evaluated and optimized: 750 µL sample at pH 7.5, 40 mg adsorbent, 250 µL hexane as a washing solvent, and 750 µL acetonitrile as eluent, resulting in recoveries around 74%. Linearity was acceptable in the 100-3000 ng mL-1 range, and the selectivity and accuracy were also suitable. The limits of detection and quantitation were 30 and 50 ng mL-1, respectively. The adsorbent effectively removed 87% of the proteins and may be reused three times. The analytical approach was successfully verified and used to analyze enalapril in urine samples collected from volunteers. Finally, the greenness of the researched technique was assessed using five measures that showed good eco-friendliness.

Low-volume LC-MS/MS method for the pharmacokinetic investigation of carvedilol, enalapril and their metabolites in whole blood and plasma: Application to a paediatric clinical trial

Evidence-based pharmacotherapy with carvedilol and enalapril in children suffering from heart failure is insufficient owing to limited pharmacokinetic data. Although a few data sets regarding enalapril, its metabolite enalaprilat and carvedilol in children have been published, pharmacokinetic data on carvedilol metabolites are missing. However, for both drug substances, their active metabolites contribute substantially to drug efficacy. As data can hardly be derived from adults owing to the unknown impacts of enzymatic maturation and ontogeny during childhood, customised assays are important to facilitate paediatric evidence-based pharmacotherapy. Considering ethical paediatric constraints, a low-volume liquid chromatography coupled to mass spectrometry (LC-MS/MS) assay was developed using whole blood or plasma for the quantification of enalapril, enalaprilat, carvedilol, O-desmethyl carvedilol, 4- and 5-hydroxyphenyl carvedilol as well as 3- and 8-hydroxy carvedilol. To facilitate broader applications in adults, the elderly and children, a wide calibration range-between 0.024/0.049 and 50.000 ng/ml-was achieved with good linearity (r ≥ 0.995 for all analytes). In compliance with international bioanalytical guidelines, accuracy, precision, sensitivity and internal standard normalised matrix effects were further successfully validated with the exception of those for 3-hydroxy carvedilol, which was therefore assessed semi-quantitatively. Distinct haematocrits did not impact matrix effects or recoveries when analysing whole blood. Blood-to-plasma ratios were determined for all analytes to form the basis for pharmacokinetic modelling. Finally, incurred sample reanalysis of paediatric samples confirmed the reproducibility of the developed low-volume LC-MS/MS method during study sample analysis. The assay facilitates the reliable generation of important data and contributes towards a safe drug therapy in children.

LC-MS/MS method for screening of intoxication and drug adherence of angiotensin-converting enzyme inhibitors in plasma

Aim: Intentional and accidental drug intoxication as well as medication adherence require sensitive and reliable analytical screening methods. Such methods are often lacking in children and adults, therefore, a reliable analytical method has been developed by using low plasma volume. Materials & methods: Sample preparation from plasma was achieved by solid-phase extraction process. LC-MS in positive ion mode was performed using X-select CSH™ C18 column. The mobile phase consisted of water and acetonitrile acidified with 1% formic acid using a gradient method with total run time of 10 min. Results: The method showed repeatability for all analytes. The linearity range from 0.78 to 100 ng/ml per analyte was established with recoveries ≥87% and matrix effect for all analytes was within guideline limits. Conclusion: The screening method was successfully validated for monitoring of intoxication and medication adherence of ten analytes in 50 μl residual plasma samples of children and adults.

A feasibility study prior to an international multicentre paediatric study to assess pharmacokinetic/pharmacodynamic sampling and sample preparation procedures, logistics and bioanalysis

Background

Variability in pre-analytical procedures such as blood sampling, sample preparation and transport can substantially influence bioanalytical results and subsequently impair reliability of data gathered during clinical trials. Especially in vulnerable populations, all efforts should be made to facilitate high-quality data extraction excluding unnecessary or repeated intervention.

Methods

The EU-funded LENA project (Labeling of Enalapril from Neonates up to Adolescents) included a feasibility study in its preparatory procedures prior to first-in-child studies. Derived from a regular study visit, it encompassed all procedures, from sampling of two study-specific drugs and four sensitive humoral parameters to bioanalysis, to evaluate the quality of obtained samples and applicability of logistical and bioanalytical procedures. Drug administration to healthy adults was circumvented by pre-spiking the blood collection tubes with a drug solution. Five clinical sites were evaluated.

Results

Clinical teams' preparedness and applicability of required sampling procedures was investigated in 18 volunteers, on-site. 97% of collected pharmacokinetic (PK) samples and 93% of samples for humoral parameters were obtained eligibly. Results met expectations, though one team had to be re-trained and performed a re-run. Planned procedures for sampling, sample preparation, transport and analysis were found to be suitable for being applied within paediatric trials.

Conclusion

The concept of the presented feasibility study that simultaneously assesses PK/PD sampling, sample preparation, logistics and bioanalysis proved to be a promising tool for trial preparation. It revealed improperly installed processes and bottlenecks that required adjustments prior to start of recruitment. It facilitated high-quality conduct from the first moment of paediatric pivotal studies.