A double-blind crossover study of two cyclobenzaprine regimens in primary fibromyalgia syndrome

In a double-blind crossover study, the efficacy and tolerability of oral cyclobenzaprine administered in two different regimens were compared in 40 patients affected by primary fibromyalgia syndrome. The patients were randomly divided into two groups. Each group of 20 patients was treated for 15 days with either a single dose of 10 mg/day cyclobenzaprine at bedtime or 30 mg/day cyclobenzaprine in three equal doses daily. Following treatment there was a 15-day washout period before the groups were crossed over to the other treatment. Both regimens resulted in a significant decline in the number of tender points; significant improvements were also reported in the quality of sleep, anxiety, fatigue, irritable bowel syndrome and stiffness. There was no significant difference in efficacy between the two therapeutic regimens at any stage during the trial. The frequency of reported side-effects was significantly greater (P < 0.001) when patients received 30 mg/day cyclobenzaprine (26 patients, 84%) than when they received 10 mg/day (10 patients, 27%). A dose of 10 mg cyclobenzaprine at bedtime significantly improved the symptomatology of patients affected by primary fibromyalgia syndrome. The higher dose did not further reduce these symptoms but did result in a higher incidence of side-effects.