Objective.—To assess the efficacy of tizanidine hydrochloride versus placebo as adjunctive prophylactic therapy for chronic daily headache (chronic migraine, migrainous headache, or tension-type headache).
Background.—Tizanidine is an α2-adrenergic agonist that inhibits the release of norepinephrine at both the spinal cord and brain, with antinociceptive effects that are independent of the endogenous opioid system. Previous open-label studies have suggested the drug may be effective for treatment of chronic daily headache.
Methods.—Two hundred patients completed a 4-week, single-blind, placebo baseline period, with 134 fulfilling selection criteria and then randomized to tizanidine or placebo. Ninety-two patients completed at least 8 weeks of treatment (tizanidine, n = 45; placebo, n = 47), and 85 patients completed 12 weeks of treatment (tizanidine, n = 44; placebo, n = 41). Most patients (77%) met the diagnostic criteria for migraine of the International Headache Society; 23% had either chronic migrainous headache or chronic tension-type headache. Tizanidine was slowly titrated over 4 weeks to 24 mg or the maximum dose tolerated (mean, 18 mg; SD, 6.4; median, 20.0; range, 2 to 24), divided equally over three dose intervals per day. Overall headache index ([headache days × average intensity × duration in hours]/28 days) was the primary end point.
Results.—Tizanidine was shown to be superior to placebo in reducing the overall headache index (P = .0025), as well as mean headache days per week (P = .0193), severe headache days per week (P = .0211), average headache intensity (P = .0108), peak headache intensity (P = .0020), and mean headache duration (P = .0127). The mean percentage improvement during the last 4 weeks of treatment with tizanidine versus placebo was 54% versus 19% for the headache index (P = .0144), 55% versus 21% for severe headache days (P = .0331), 35% versus 19% for headache duration (P = .0142), 35% versus 20% for peak headache intensity (P = .0106), 33% versus 20% for average headache intensity (P = .0281), and 30% versus 22% for total headache days (P = .0593). Patients receiving tizanidine also scored higher ratings of overall headache improvement on a visual analog scale (P = .0069). There was no statistically significant difference in outcome for patients with chronic migraine versus those with only migrainous or tension-type headache. Adverse effects reported by more than 10% of the patients included somnolence (47%), dizziness (24%), dry mouth (23%), and asthenia (19%). Dropouts due to adverse events did not differ significantly between tizanidine and placebo.
Conclusions.—The results support tizanidine as an effective prophylactic adjunct for chronic daily headache, including migraine, migrainous headache, and tension-type headache. These results also suggest the possible importance of an α2-adrenergic mechanism underlying the pathophysiology of this spectrum of headache disorders.