tokens: Seventy - one participants completed 2 separate study days and were blind to medication condition ( placebo , 10 - mg oxycodone ). Plasma oxycodone concentration peaked between 60 and 90 minutes postdose ( P <. 01 ) and pupil size , an indication of physiological effects of the medication , peaked at approximately 90 to 120 minutes postdose ( P <. 01 ). Significant declines in simple and sustained attention, working memory, and verbal memory were observed at 1 hour postdose compared to baseline for both age groups with a trend toward return to baseline by 5 hours postdose .