One hundred and thirty-nine paired plasma/saliva samples were collected from 43 cancer patients who had been taking SR oxycodone for more than 5 days at doses ranging from 10 to 600 mg/day (median 40 mg/day). Plasma concentrations of oxycodone and noroxycodone ranged from 1.0 to 256.0 and 0.9-269.4 μg/L, respectively. Salivary concentrations of oxycodone (range 0.93-3,620, mean 336 μg/L) were much higher than plasma concentrations (mean 38.2 μg/L)