Presented at the 2013 AAPM Annual Meeting « Back

Gender and Placebo Analgesic Response in Chronic Knee Osteoarthritis Pain Model

Joseph Graciosa, BA, jgraciosa@ric.org¹, Meryem Saracoglu, MD², Amy Kirsling, MPA¹, Maxine M. Kuroda, PhD MPH¹, Bruni Hirsch, MSPH¹, R. Norman Harden, MD¹, Kelly N. Comstock, Bachelor's Degree¹, (1) Rehabilitation Institute of Chicago, Chicago, Illinois, (2) Northwestern University Feinberg School of Medicine, Chicago, Illinois

Objective: An interim analysis of the placebo effect versus gender in the single blind placebo lead in phase (SBPL) of a pharmaceutical trial on knee osteoarthritis (KOA). Methods: The first 34 participants with KOA pain (23 women) were abstracted from the SBPL phase of a trial testing the efficacy of milnacipran in treating chronic KOA pain. Data from the SBPL period were analyzed at baseline (V1) and first follow up visit (end of SBPL; V2). Gender differences were analyzed for pain metrics (VAS and McGill Pain Questionnaire-SF scores) and the demographic and psychosocial contributors to pain report. Results: Females and males did not differ in age, body mass index, duration of pain, and education. Using multivariable linear regression models depression and anxiety scores were nonsignificantly higher for males than for females at V1 and V2. Change in VAS (V2 minus V1) differed between males and females (8.5 v -14.2 [i.e. pain increased in Males]; p=.02). Similar results were observed between males and females for MPQ-SF scores (6.1 v -1.9; p<0.01). Male gender (p = .05) and education (p = .05) were independent contributors to differences in VAS and MPQ SF scores in SBPL. Depression (p = .02) was an additional contributor to difference in MPQ SF scores. Conclusion: Our results indicate gender differences in pain perception/placebo response; a robust placebo response in females and an apparent nocebo response in males. The potential trial design implications of this preliminary work will be discussed.

Funding: Forest Laboratories, Inc.