NEW YORK, NY -- February 8, 2008 -- Botulinum toxin Type A (Botox and Botox Cosmetic) and botulinum toxin Type B (Myobloc) have been linked to serious adverse reactions, including respiratory failure and death. The most severe adverse effects were found in paediatric patients treated for limb spasticity associated with cerebral palsy.
The adverse reactions mimic symptoms of botulism, including difficulty swallowing, weakness, and breathing problems, and appear to be related to the spread of the toxin to areas distant from the injection site. The US Food and Drug Administration is conducting an ongoing safety review. Early findings suggest overdosing may be contributing to the adverse reactions.
The adverse effects occurred following treatment for both FDA-approved and nonapproved indications. In the United States, botulinum toxins are not approved for the treatment of limb spasticity in children or adults, though the FDA is aware of the body of literature describing this use.
Botulinum toxin Type A is approved for treatment of conditions such as blepharospasm, cervical dystonia, and severe primary axillary hyperhydrosis. Botulinum toxin Type A is also approved for temporary improvement in the appearance of moderate to severe facial frown lines. Botulinum toxin Type B is approved for the treatment of adults with cervical dystonia; the safety and effectiveness of botulinum toxin Type B for cervical dystonia in children have not been established.
The FDA is not advising healthcare professionals to discontinue prescribing these products. However, until the FDA safety review is completed, the agency recommends that healthcare professionals who use medicinal botulinum toxins take the following precautions:
-- Understand that potency determinations expressed in "Units" or "U" are different among the botulinum toxin products; clinical doses expressed in units are not comparable from one botulinum product to the next.
-- Be alert to the potential for systemic effects following administration of botulinum toxins such as: dysphagia, dysphonia, weakness, dyspnea or respiratory distress.
-- Understand that these effects have been reported as early as 1 day and as late as several weeks after treatment.
-- Provide patients and caregivers with the information they need to be able to identify the signs and symptoms of systemic effects after receiving an injection of a botulinum toxin.
-- Tell patients they should receive immediate medical attention if they have worsening or unexpected difficulty swallowing or talking, trouble breathing, or muscle weakness.
SOURCE: US Food and Drug Administration