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Combined Effects of Morphine and Distraction and Morphine and Positive Mood Changes on Tonic Pain

Principal Investigator: Charles S. Cleeland, Ph.D.

The proposed studies test our working model that behavioral interventions intended to reduce pain should coincide not only with differences in pain types (phasic or tonic) but also with our preliminary knowledge of the neurophysiological substrates of sensory and reactive pain components. This protocol focuses on two components of behavioral pain control, mood alteration and distraction, that will be given in the presence or absence of morphine, the prototypic drug for aggressive pharmacological pain management.

Specific Goals

  • Study 1A: To examine the combined effects of morphine and a behavioral intervention (mental distraction) on pain tolerance and pain rating (both intensity and unpleasantness) in normal subjects (Complete)
  • Study 1B: To examine the combined effects of morphine and a behavioral intervention (positive mood induction) on pain tolerance and pain ratings (both intensity and unpleasantness) in normal subjects (Complete)


Subjects will complete a series of survey questionnaires before, during and after being randomly given an oral dose of either morphine or placebo. The pain stimulus will be pressure produced by the pressure algometer (PA). On Day 2, subjects for Study 1A will be randomly assigned to one of the four conditions (morphine and distraction, morphine alone, placebo and distraction or placebo) and subjects for Study 1B will be randomly assigned to one of seven conditions (morphine plus positive mood, morphine plus neutral mood, morphine alone, active placebo plus positive mood, active placebo plus neutral mood, active placebo alone or placebo). The study drugs will be either immediately release morphine sulfate (30 mg p.o.) or diphenhydramine (50 mg p.o.) (active placebo), which should mimic at least some of the non-analgesic effects of morphine. Study intervention will include a distraction task or none for Study 1A, or randomization to a neutral or positive mood or none for Study 1B. The addition of the control group with no treatment (unmedicated syrup base) will make it possible to assess where there is an order-related, nonspecific increase in tolerance time and/or decrease in ratings.

There will be two experimental sessions. On Day 1, subjects will be screened to determine study eligibility. In Session 1, baseline ratings of intensity and unpleasantness and pressure pain tolerance time will be recorded for all subjects. In Session 2, subjects will complete a baseline PA task, then be assigned to one of the experimental groups and will complete the PA task following an appropriate treatment. Those subjects who are assigned to morphine will have blood drawn for assay.


The outcome measures include 1) tolerance time, in seconds, for each pressure algometer session, 2) the Outcome Expectancy and Self-Efficacy (OESE), 3) the PASAT task, 4) the Profile of Mood States (POMS) and 5) the post experimental questionnaire.

For more information

Contact Karen O. Anderson, Ph.D., at

© 2014 The University of Texas MD Anderson Cancer Center