Incorporation of capillary microsampling into whole body plethysmography and modified Irwin safety pharmacology studies in rats.

UNLABELLED: Limited toxicokinetic data is generated during modified Irwin screen and whole body plethysmography safety pharmacology studies, due to disturbance of primary endpoints by standard blood sampling methods. We evaluated if incorporation of microsampling would impact on data quality, as providing toxicokinetic data from main test animals could reduce the need for satellite animals.

METHODS

A modified Irwin screen was performed, testing oral clonidine (0, 0.03, 0.1, or 0.3 mg/kg). One cohort of rats per dose level underwent standard blood sampling (post-4 h Irwin assessment), and another cohort underwent microsampling after the 0.5, 1, 2, 4 and 24 h Irwin assessments. The respiratory effects of oral theophylline (0 or 10 mg/kg) and oral baclofen (0 or 5 mg/kg), were tested using whole body plethysmography. Groups of animals underwent standard blood sampling (at end of recording at 4 h post-dose) or microsampling at either 0.5 h or 1 h intervals (4 or 8 microsamples, respectively).

RESULTS

Microsampling did not impact on the quality of the data generated. The expected effects of clonidine on behavioural parameters, and of theophylline and baclofen on changes in ventilatory parameters were observed at a similar magnitude and duration independent of sampling method.

DISCUSSION: The incorporation of multiple capillary microsamples into the modified Irwin or respiratory study did not adversely affect the primary endpoints. The capillary microsampling method is a refinement in blood sampling technique which can easily be adapted into safety pharmacology studies to generate pharmacokinetic profiles within the same animal as the primary data, thus enhancing scientific robustness and reducing the satellite animals required.