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To assess the efficacy of 4% topical lidocaine in spheno-palatine blocks, a randomized controlled trial was carried out on patients with chronic muscle pain syndromes. Sixty-one patients (42 with fibromyalgia (FM) and 19 with myofascial pain syndrome (MPS)) completed the trial. Outcome measures included pain intensity, a daily pain diary, headache frequency, sensitivity to pressure using a dolorimeter, anxiety, depression, and sleep quality. Patients were randomized to receive either 4% lidocaine or sterile water (placebo) 6 times over a 3-week period. Both subjects and investigators were blind to treatment allocation. The results showed that 4% lidocaine had no superiority over placebo in any of the outcome measures. Twenty-one subjects (35%) showed a decrease in pain which was greater than 30% of their baseline value. Of these 21 subjects, 10 received lidocaine and 11 received placebo. These data suggest that, in this population, 4% lidocaine is no better than placebo in the treatment of chronic muscle pain.