Sustained onabotulinumtoxinA therapeutic benefits in patients with chronic migraine over 3 years of treatment.

Background: Evidence on whether the therapeutic effect and good safety profile of onabotulinumtoxinA (Botox®) in chronic migraine (CM) patients is maintained over long term treatment is still limited. We herein aimed at assessing whether there is a sustained benefit and good safety with repeated onabotulinumtoxinA sessions in CM over more than three years of treatment.

Methods: We prospectively enrolled 65 CM patients, who were classified as responders after three sessions of onabotulinumtoxinA and were eligible to further continue treatment. Data documenting longitudinal changes from the trimester after the third onabotulinumtoxinA administration (T1) to the trimester after completing two years of treatment (T2) and eventually to the trimester after completing three years of treatment (T3) in (i) mean number of monthly headache days (ii) migraine severity as expressed by the mean number of days with peak headache intensity of > 4/10, and (iii) mean number of days with use of any acute headache medication, were prospectively collected from patients' headache diaries.

Results: A total of 56 (86.1%) of 65 patients achieved to attain onabotulinumtoxinA over three years. At T3, a significant reduction in mean monthly headache days was evident, compared to T1 (3.4 ± 1.7 vs 7.2 ± 3.8; P < 0.001) with diminished mean number of monthly days with peak headache intensity of more than 4/10 and a significant change in days using acute headache medications per month between T1 and T3 (2.8 ± 1.3 vs 4.7 ± 3.2; P < 0.001). Significant changes were also noticed in all efficacy variables from T2 to T3. Therapy was safe and well tolerated with low rates of adverse events or drop-outs.

Conclusion: The long -term treatment with onabotulinumtoxinA proved effective, safe and well tolerated over three years. Our findings support the strategy to consistently deliver sessions of use of onabotulinumtoxinΑ over long time in CM patients (Trial registration NTC03606356, registered retrospectively, 28 July 2018).