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. 2022 May 9;7(9):e156973. doi: 10.1172/jci.insight.156973

Figure 5. Integrated pharmacokinetic/pharmacodynamic model.

Figure 5

αB, αF: intrinsic activity of buprenorphine and fentanyl, respectively (which also accounts for receptor reserve); B, F: effect site concentrations for buprenorphine and fentanyl, respectively; BR, FR: concentrations of receptors bound to buprenorphine and fentanyl, respectively; BUP: buprenorphine; ke0,B, ke0,F: equilibration rate constants for buprenorphine and fentanyl, respectively; kON,B, kOFF,B: buprenorphine association and disassociation rate constants; kON,F, kOFF,F: fentanyl association and disassociation rate constants; R: concentration of unbound receptors; VB: baseline ventilation; VE: minute ventilation. Because fentanyl associates and dissociates rapidly from the receptors, C50,F (=kOFF,F/kON,F) was estimated in place of kOFF,F and kON,F.