Precision Dosing of Doxapram in Preterm Infants Using Continuous Pharmacodynamic Data and Model-Based Pharmacokinetics: An Illustrative Case Series

INTRODUCTION

Current drug dosing in preterm infants is standardized, mostly based on bodyweight. Still, covariates such as gestational and postnatal age may importantly alter pharmacokinetics and pharmacodynamics. Evaluation of drug therapy in these patients is very difficult because objective pharmacodynamic parameters are generally lacking. By integrating continuous physiological data with model-based drug exposure and data on adverse drug reactions (ADRs), we aimed to show the potential benefit for optimized individual pharmacotherapy.

MATERIALS AND METHODS

Continuous data on oxygen saturation (SpO2), fraction of inspired oxygen (FiO2) and composite parameters, including the SpO2/FiO2 ratio and the cumulative oxygen shortage under the 89% SpO2 limit, served as indicators for doxapram effectiveness. We analyzed these continuous effect data, integrated with doxapram exposure and ADR parameters, obtained in preterm infants around the start of doxapram therapy. The exposures to doxapram and the active metabolite keto-doxapram were simulated using a population pharmacokinetic model. Infants were selected and retrospectively compared on the indication to start doxapram, the first response to doxapram, a potential dose-response relationship, and the administered dosage over time. Recommendations were made for individual improvements of therapy.

RESULTS

We provide eight cases of continuous doxapram administration that illustrate a correct and incorrect indication to start doxapram, responders and non-responders to therapy, and unnecessary over-exposure with ADRs. Recommendations for improvement of therapy include: objective evaluation of added effect of doxapram after start, prevention of overdosing by earlier down-titration or termination of therapy, and the prevention of hypoxia and agitation by measuring specific parameters at strategical time-points.

CONCLUSION

Real-time and non-invasive effect monitoring of drug therapy combined with model-based exposure provides relevant information to clinicians and can importantly improve therapy. The variability between and within patients emphasizes the importance of individual, objective evaluation of pharmacotherapy. These measurements, together with data on ADRs, allow for precision medicine in neonatology that should be brought to the bedside.

A diagnostic tool for self-poisoned patients: Analysis of gastric content and lavage fluids

Approximately 500 patients per year are admitted to the emergency department (ED) of the Erasmus University Medical Center presenting with intoxications with medication. For adequate treatment, it is sometimes important to know which drugs in which quantities were ingested. This can require laboratory analysis of blood or urine samples; however, these samples do not provide information about the possible effects that can still be expected. We performed toxicological screening on the gastric content of three patients admitted to our ED in January and February 2018. These patients underwent gastric lavage or received a gastric tube as part of routine care. The gastric fluid was analysed via UPLC-MS/MS using the Waters method for toxicological screening. In all three patients, we successfully determined drugs in the gastric content. In two patients, we identified more different drugs in the gastric content than in blood plasma. In the other patient, admitted approximately six hours after a severe autointoxication with the betablocker metoprolol, we found significant amounts of metoprolol in the gastric content acquired by gastric lavage. We therefore believe that analysis of gastric content after an intoxication can have multiple applications; for example, it may provide information about symptoms of intoxication that can be expected, it may aid patient care and may provide insight in the toxicokinetics of different drugs. In conclusion, we demonstrate that toxicological screening and quantification of drug levels in gastric content is possible and has potential as an adjunct in patient care, but limitations need to be addressed before implementation in clinical practice.