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This study assessed the absolute and relative bioavailabilities and transmucosal and gastrointestinal absorbency of fentanyl buccal tablet (FBT) and oral transmucosal fen-tanyl citrate (OTFC). In a randomized crossover design, 26 healthy subjects received FBT 400 μg (transmucosal), FBT 800 μg (oral), OTFC 800 μg (transmucosal), and fentanyl 400 μg (intravenous). The transmucosal FBT had the highest absolute bioavailability (0.65) compared with the oral FBT (0.31) or transmucosal OTFC (0.47). More fentanyl was absorbed transmucosally from FBT than OTFC (48% vs 22%). Median tmax values were shorter following the transmucosal FBT (47 minutes) than the oral FBT (90 minutes) or the transmucosal OTFC (91 minutes). Transmucosal administration of FBT compared with dose-normalized OTFC resulted in higher total systemic fentanyl exposure, higher early systemic exposure, and higher Cmax. The rate and extent of fentanyl absorption were greater following administration of FBT compared to OTFC. An approximately 30% smaller dose of FBT achieved systemic exposures comparable to OTFC.