Clinical use of non-A botulinum toxins: botulinum toxin type B.

Botulinum neurotoxin type B (BT, BT-B) has been used as NeuroBloc/MyoBloc since 1999 for treatment of cervical dystonia, hyperhidrosis, spastic conditions, cerebral palsy, hemifacial spasm, bladder dysfunction, spasmodic dysphonia, sialorrhoea, anal fissures, piriformis syndrome, various pain conditions and cosmetic applications. Generally, its therapeutic effects are comparable to BT type A (BT-A). The adverse effect profiles of BT-B and BT-A, however, differ considerably. BT-B has been found to produce more regional as well as systemic anticholinergic adverse effects, such as dryness of mouth, accommodation difficulties, conjunctival irritation, reduced sweating, dysphagia, heartburn, constipation, bladder voiding difficulties and dryness of nasal mucosa. In BT-B the relationship between autonomic and motor effects known from BT-A is substantially shifted towards autonomic effects. BT-B, therefore, should be used carefully in patients with autonomic disorders and in patients with concomitant anticholinergic therapy. If NeuroBloc/MyoBloc is used to treat cervical dystonia patients with antibody-induced failure of BT-A therapy, 86% of those will develop complete secondary therapy failure after five applications. If NeuroBloc/MyoBloc used to treat cervical dystonia patients without prior exposure to BT, 44% of those will develop complete secondary therapy failure after nine applications. NeuroBloc/MyoBloc, therefore, is associated with substantial antigenicity problems originating from a particular low specific biological potency. Systemic anticholinergic adverse effects and high antigenicity limits the clinical use of NeuroBloc/MyoBloc considerably.