This represents a series of two laboratory studies examining several components of behavioral pain control: mood alteration and distraction. A critical feature is the examination of these behavioral components in the presence of morphine, the prototypic drug for aggressive pharmacologic pain management. It is recognized that behavioral control of pain, if used at all, will often be used in conjunction with analgesics.
The specific aims of the study are (a) to examine the combined effects of morphine and mental distraction on pain tolerance and pain ratings of intensity and unpleasantness in normal subjects, and (b) to examine the combined effects of morphine and positive mood induction on pain tolerance and pain ratings of intensity and unpleasantness in normal subjects. The pain stimulus will be pressure to the index finger produced by a pressure algometer. Subjects in Study A are randomly assigned to 1 of 5 conditions: morphine with distraction, morphine alone, active placebo with distraction, active placebo alone, and inactive placebo. This study has commenced in the University Clinical Research Center (CRC) at Hermann Hospital. During the second year of the award, we initiated this study in the University Clinical Research Center (CRC) at Hermann Hospital. The hypothesis for Study A is that the combined use of distraction and morphine will have the greatest effect on pain perception, followed in order by: morphine alone, distraction with an active placebo (diphenhydramine), an active placebo, and an inactive placebo. Eight subjects (three females, five males) were enrolled in the pilot phase of the study. Some minor adjustments in the study procedures were necessary. The tonic pain stimulus is pressure stimulation from the pressure algometer. We initially used 1.0 kg of weight on the algometer but subsequently increased the weight to 2.0 kg. This increase was indicated as the subjects' baseline pain tolerance was greater than the 5-minute limit for the pressure stimulus. We also adjusted the timing of the baseline blood draw in order to avoid influencing the subjects baseline pain tolerance. In addition, minor changes were made in the instructions for the distraction task in order to make the task requirements easier to comprehend. Subjects in Study B will be assigned to 1 of 7 conditions: morphine with positive mood, morphine with neutral mood, morphine alone, active placebo with positive mood, active placebo with neutral mood, active placebo alone, and inactive placebo. The primary outcome variable will be change in pain tolerance time. Secondary outcome measures will be changes in pain intensity and unpleasantness ratings.
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