Table 1. Results of Linear Mixed-Effects Modeling of Five Experimental Pain Tests: The Final Models

The baseline effect equals the maximal tolerated stimulus intensity at baseline for electrical, pressure and heat pain, and the area under the VAS-time curve for ice water and ischemic pain.

E⁰= baseline effect when no drug is present in the linear model; K^a= slope parameter alfentanil; K^p= slope parameter placebo; K^t= slope parameter time; ς²= SD of the effect in an individual subject (residual and intra-individual error); −2LL = minimum value of nonlinear mixed-effects model objective function according to the likelihood ratio test; SE = standard error of the parameter estimate; CV = coefficient of variation of the parameter estimate in the study population; NS = not significant.