Fig. 5.
Steady-state relationship between R-dihydroetorphine plasma or effect-site concentration (conc.) and effect (effect = 1 is pre-drug baseline effect). Pain relief: blue line; ventilation: red line. The red and blue dots are the C50 values: C50,V is the R-dihydroetorphine concentration causing a 50% reduction in ventilation in between baseline ventilation and the apparent minimum ventilation (VMIN, grey line), and C50,A the R-dihydroetorphine concentration causing a 50% increase in current intensity at which a pain response is reported. The yellow line the concentration-ventilation response curve modeled by equation 1 (in the Pharmacokinetic-pharmacodynamic Analysis section) without trend term C.