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.