If interaction between treatments is significant, the ANCOVA model with interaction will estimate the treatment effects for each of the four groups. This model is able to test all 6 contrasts between the four combinations. A hierarchical (gatekeeping) testing strategy to maintain a family-wise error rate will be adopted as the following: the first stage will compare desipramine or lidocaine individually to placebo with multiplicity-adjusted p-values. If a significant difference (one or both null hypotheses rejected) is found for either or both individual agents, then the analysis will proceed to the second-stage of hypothesis which will compare the effects of the active desipramine/active lidocaine treatment to the double placebo. If a significant difference (null hypothesis rejected) is found for combined therapy over placebo based on the multiplicity-adjusted p-value, then the final (tertiary) stage of comparison will be performed comparing combined therapy to individual therapy. In the hierarchical (gatekeeping) testing procedures, inferences in each stage depend on the acceptance or rejection of null hypotheses in all previously stages, and each stage serves as a gatekeeper for the stages later in the sequence. In our strategy for the model with significant interaction effect, if at least one hypothesis has been rejected, then the next stage of hypotheses will be tested, and the family-wise error rate is controlled at the .05 level.