Safety of botulinum toxin short interval therapy using incobotulinumtoxin A

The therapeutic efficacy of botulinum toxin (BT) can be completely blocked by formation of BT antibodies (BTAB), thus producing antibody-induced therapy failure (ABTF). One of the risk factors for this is the interval between two subsequent injection series. To prevent BTAB formation it is universally recommended not to use interinjection intervals of less than 12 weeks. However, BT's therapeutic efficacy may be considerably shorter than this interval, thus causing substantial reduction of quality of life. We wanted to study whether BT therapy with interinjection intervals of less than 12 weeks (short interval therapy, SIT) would be immunologically and otherwise safe. To minimise the risk of BTAB formation we used incobotulinumtoxin A which has a particularly low antigenicity. Altogether 30 patients (age 59.2 ± 13.5 years. 19 females, 11 males) with different dystonias were included in this study. They received SIT with incobotulinumtoxinA (Xeomin^®, Merz Pharmaceuticals, Frankfurt/M, Germany) at interinjection intervals of 69.0 ± 8.1 days (equal 9.9 weeks or 2.2 months, min 48.9 ± 2.4 days) for 14.3 ± 2.9 injection series (equal 906 ± 169 days or 2.5 ± 0.5 years) in a dose of 259 ± 159 MU (max 670 ± 144.4 MU). None of the patients showed signs of ABTF, unusual BT effects or increased adverse effects. Information provided by this study confirms safety of SIT. With a considerable percentage of patients hitherto undertreated for prolonged periods of time with BT therapy applying 12 weeks intervals, SIT may substantially improve the quality of life for those patients. Whether SIT is also safe with other BT drugs needs to be tested.