BACKGROUND

Onabotulinum toxin A (OnA) is a well-tolerated and effective treatment for chronic migraine (CM). However, based on research indications that incobotulinum toxin A (InA) would be equally effective, a Veterans' Health Administration Medical Center mandated a 2-year trial of InA as more cost-effective alternative to OnA. Although InA is used for many similar indications as OnA, it is not Food and Drug Administration approved for treating CM, and complications occurred in several patients with CM following this treatment change. We conducted this retrospective analysis to evaluate differences in the efficacy of OnA and InA and identify the reasons for the adverse effects of InA in some of these patients.

METHODS

We performed a retrospective review of 42 patients who had been effectively treated with OnA and were then switched to InA. The differences between treatment responses to OnA and InA were assessed through the evaluation of pain on injection, number of headache days, and duration of action. Patients received injections at 10- to 13-week intervals. Those who reported excessive pain on injection of InA were switched back to OnA.

FINDINGS

Severe burning pain on injection was reported by 16 (38%) patients for InA only and by 1 (2%) patient for both InA and OnA. Neither migraine suppression nor the duration of effect was significantly different between OnA and InA.

CONCLUSIONS

Reformulation of InA with a pH-buffered solution may eliminate the difference in pain on injection. InA would then be a good alternative to OnA for treating CM.