The Wearing-Off of OnabotulinumtoxinA in Patients with Chronic Migraine: Experience of a Tertiary Portuguese Centre

Introduction: The onabotulinumtoxinA (onabotA) is an injectable preventive treatment of chronic migraine (CM), administered in 12 week’s intervals. Some patients present a wearing-off (WO) effect in the last weeks before the next treatment. The aim of our study was to evaluate the WO phenomen in patients under onabotA treatment and to recognize possible predictive features of the phenomena. Methods: We designed a cross-sectional study and proceeded to demographic and clinical characterization of a group of patients, and evaluation of onabotA therapeutic response and adverse events. WO effect was defined as the loss of therapeutic effect, that consists of reduction equal or greater than 50% in the number of headache days, before the 12-week interval. Statistical testing was carried out using a level of significance of p <0.05. Results: We included 60 patients (95.1% female) with a mean age of 49.0±11.4 years. On average, before onaBotA treatment patients had around 15.0 attacks per month. In 45.3% we noticed a therapeutic response after the first treatment. The WO effect was noticed in 36 patients (66.7%) and the majority (50.9%) between the 10 th to 12 th week post treatment. Wearing-off was more reported by patients under 155 units PREEMPT protocol ( p =0.032). Conclusion: This study documents the high frequency of WO phenomen in patients with chronic migraine under onabotA. Therefore, the possibility of a different protocol in selected patients must be explore with larger observational and prospective studies as well as evaluation in clinical trials.