Figure 11-31 The mean absorption of opioids after 10 minutes in the oral cavity of normal subjects. The pH of the dosing solution was 6.5. MS, morphine sulfate; OXY, oxycodone; LEVO, levorphanol; HM, hydromorphone; NAL, naloxone; METH, methadone; HER, heroin; FENT, fentanyl; BUP, buprenorphine. (From Weinberg DS, Inturrisi CE, Reidenberg B, et al: Sublingual absorption of selected opioid analgesics. Clin Pharmacol Ther 44:335–342, 1988.)