COMPARISON OF AMITRIPTYLINE, CYCLOBENZAPRINE, AND PLACEBO IN THE TREATMENT OF FIBROMYALGIA - A RANDOMIZED, DOUBLE-BLIND CLINICAL-TRIAL

Objective. To compare the relative efficacy and tolerability of amitri ptyline, cyclobenzaprine, and placebo in the treatment of fibromyalgia , and to identify predictors of response to amitriptyline and cycloben zaprine. Methods. Two hundred eight patients who fulfilled the America n College of Rheumatology criteria for the classification of fibromyal gia were entered into a 6-month prospective, double-blind, multicenter trial and were randomized to 1 of 3 treatment groups: amitriptyline, cyclobenzaprine, or placebo. Results. After 1 month, 21%, 12%, and 0% of the amitriptyline, cyclobenzaprine, and placebo patients, respectiv ely, had significant clinical improvement (amitriptyline versus placeb o P = 0.002, cyclobenzaprine versus placebo P = 0.02, amitriptyline ve rsus cyclobenzaprine P not significant). These percentages increased t o 36%, 33%, and 19%, respectively, at the 6-month assessment (P not si gnificant). The nature and frequency of side effects reported by patie nts treated with amitriptyline and those reported by patients treated with cyclobenzaprine were similar. A normal Minnesota Multiphasic Pers onality Inventory (MMPI) profile at baseline was predictive of clinica l improvement at the 1-month evaluation (odds ratio 3.3, 95% confidenc e interval 1.2-9.0). However, neither the MMPI profile nor any of the demographic, clinical, or functional parameters evaluated at baseline predicted long-term response. Conclusion. Our data confirm the short-t erm efficacy of amitriptyline and cyclobenzaprine in a small percentag e of patients with fibromyalgia. Lone-term efficacy could not be demon strated because of a higher-than-expected placebo response. Predictors of response to these drugs could not be determined.