To the best of our knowledge, this is the first systematic review and meta-analysis evaluating botulinum toxin safety administration in patients with migraine.
The results show that the most frequent AEs were neck pain, followed by musculoskeletal weakness in the head and neck regions, injection site pain, and blepharoptosis or eyelid ptosis.
Hollanda et al., who assigned patients with chronic migraines to botulinum toxin or placebo groups, reported pain in injection site points as the most common AEs (
15).
In a 24-week double-blind study of Phase III REsearch Evaluating Migraine Prophylaxis Therapy (PREEMPT), Aurora et al. reported AEs in 59.7% of enrolled patients in the botulinum toxin group and 46.7% in the placebo group. Only 5.3% experienced severe AEs, and 13.2% discontinued treatment (
28). On the other hand, in the first 24 weeks of PREEMPT 2, 65.1% of patients experienced AEs, while only 4.3% had severe AEs (
43). The pooled PREEMPT 24-week analysis showed that 62.4% of onabotA-treated patients reported AEs, while only 4.8% experienced serious AEs. Most AEs were mild/moderate and self-limited, and the most common AEs were neck pain, muscle weakness, ptosis, and injection-site pain (
28,
43). In another 32-week open-label trial, Aurora et al. reported AEs in 58.3%, while 25.4% discontinued the treatment based on AEs. Like previous studies, neck pain, muscle weakness, and eyelid ptosis were the most frequent AEs (
44). Finally, in an over 56-week trial, AEs were found in 78.3% and 75.9% of cases who received 5 or 3 cycles of botulinum toxin treatment. Serious AEs were found in 7.8% and 4.9% of 5 or 3 treatment cycles. It was shown that the rate of AEs decreased after each treatment cycle (
26).
Diener et al. pooled data from 4 trials by evaluating 1997 patients with migraines and found that AEs happened in 73%, and almost all were mild/moderate (
31). It was also demonstrated that patients who received 150-200 units per cycle experienced fewer AEs than those receiving more than 200 units per cycle of botulinum toxin. Most AEs were mild, lasted for one week, and were resolved between 8 to 9 weeks.
By enrolling 254 patients with chronic migraines in the Hull Migraine Clinic, Khalil et al. found injection-site pain, neck stiffness, ptosis, headache exacerbation, and dysphagia as common AEs after onabotA injection, respectively (
41).
Dominguez et al. followed up on 725 patients with chronic migraine up to one year after administration of onabotA and showed AE incidence in 12.3% after the first dose, while 82.3% were mild/moderate and only 0.7% discontinued onabotA due to AEs (
45).
Matharu et al. followed up on 1160 patients with chronic migraines from 58 European centers, 41.2% of which reported AEs, 5.3% were serious, and 4.4% discontinued treatment (
46).
The present study had some strengths and limitations. First, we included most of all trials in this field. Second, we analyzed all related AEs.
The limitation was the difference in the dose of botulinum toxin in different studies.