Background and aims To examine the ethical, legal, and social implications (ELSI) of microdosing in exploratory paediatric research where there is exposure to background radiation and no therapeutic benefit to participants.

Methods The ethical and regulatory issues encountered in the ERA-NET PRIOMEDCHILD project ‘Paediatric Accelerator Mass Spectrometry Evaluation Research Study (PAMPER)’ were analysed. These included the project design, scientific and ethical reviews, informed consent and recruitment processes. Infants 0–2 years were recruited in Estonia and the UK to study the pharmacokinetics (PK) of acetaminophen using accelerator mass spectrometry (AMS) bioanalysis. The study was considered in the context of the scientific, regulatory, and ethical frameworks guiding Phase 0 studies in adults and children.

Results The science and ethics were developed in the protocol design and informed consent process, which resulted in approval of the study by research ethics committees in the UK and Estonia. Fifty-two babies were recruited into the study, with an acceptance rate of 50% among the parents approached. The study results demonstrated PK comparability between microdosing and therapeutic dosing in young children.

Conclusions The PAMPER study showed the feasibility and validity of microdosing AMS PK studies in children, This methodology may provide a safer and more ethically robust approach for paediatric PK studies in certain drug models than more traditional PK study designs. The parameters and validation methods for microdosing AMS PK studies need to be reflected in regulatory guidance from the EMA, FDA and other authorities.