When Standard Enrichment Skews PK Data
It was a Thursday morning in a mid-sized contract research lab. The PK staff had been chasing a 40% variability in Cmax across three identical rat studie. Diets were the same. Lights on at 6, off at 18. Same handler. But then someone noticed: the enrichment schedule differed. One cohort had rotated cardboard tubes; another had static nesting material; the third had nothing extra. The PK crew hadn't even considered enrichment as a variable. They weren't alone. In routine, the angle break when speed wins over documentation: however tight the revision looks, the pitfall is that the next person inherits an invisible assumption, and the fix takes longer than the original task would have. Standard enrichment protocol—tunnels, foragion boards, social housed—are almost never audited for pharmacokinetic impact. Yet they can alter metabolic enzymes, gastric motility, and stress axis tone.