Hypersensitivity and anaphylactic reactions may occur. Neutralizing antibody formation and loss of efficacy (with higher doses or more frequent administration). Dysphagia is common when used for cervical dystonia, and may be associated with increased risk of upper respiratory infection. Caution in neuromuscular diseases (myasthenia gravis), neuropathic disorders (amyotrophic lateral sclerosis), or patients taking aminoglycosides or other drugs that interfere with neuromuscular transmission. Formulation contains human albumin derived from blood and so theoretical but remote risk of transmission of Creutzfeldt-Jakob disease via albumin component exists (no cases identified to date). Concurrent use of botulinum toxin type A or within <4 months of type B is not recommended. Use with caution if there is inflammation, excessive weakness, or atrophy at the proposed injection site(s). Serious adverse events (including fatalities) in association with the use of botulinum types A and type B described. Incidence of autonomic effects (e.g. anticholinergic effects such as dry mouth, ptosis, accommodation difficulty) may be higher with botulinum toxin type B than with type A. Ecchymosis at the injection site reported (administer with caution to patients with thrombocytopenia or bleeding disorder or those receiving anticoagulant therapy).