[Botulinum toxin A in chronic refractory migraine: premarketing experience].

Introduction: Chronic migraine is very disabling, with medication overuse commonly associated. The recent approval of botulinum toxin-A -OnabotulinumtoxinA (OnabotA)- means a hallmark.
Aim: To describe our experience in compassionate use before approval.
Patients and Methods: 35 cases with chronic migraine assessed between July 2009-December 2011 in a specialized headache consultation. 100 U of OnabotA were injected in 21 points over the facial and pericranial muscles, according to a modified PREEMPT protocol. We determined before and after treatment: number of episodes and migraine days; pain intensity and days of disability extracted from MIDAS score, and data regarding drug intake. After follow-up, new injections were given at intervals dictated by individualized response timing. Therapeutic response was considered when: intensity of pain was reduced to a half o ≥ 4 VAS points, or the number of monthly days of pain descended ≥ 7/month, or the case converted to non-drug overuser.
Results: In 27 cases (80%) it was proved clinical improvement. This effect was confirmed by: a reduction in headache severity, reflected as much in pain intensity (VAS scale < 0.001) as in the number of days with disability (3.2 vs 0.4, p < 0.001); an improvement in the number of monthly days of pain (19.8 vs 13.8, p < 0.05; a significant decrease in the number of cases of medication overuse (69% vs 13%, p < 0.01). Mean duration of effect was 15 weeks and mean follow-up 9.8 months.
Conclusions: OnabotA disclosed efficacy as prophylactic treatment of chronic migraine. It is mainly expressed as a reduction of pain intensity. Medication overuse also descended. Adverse events were sparse.