The FDA has announced that boxed warnings are now included on labels of four botulinum toxin drug products, revising a previous safety alert on the products. The products also now include medication guides for patients, as mandated by FDA in April.

The new warning advises that botulinum toxin’s effects can spread from the injection site to other parts of the body, leading to symptoms similar to those of botulism such as extreme difficulty swallowing and breathing difficulties.

Reports of the symptoms primarily have been documented in children with cerebral palsy who receive botulinum toxin for muscle spasticity, an off-label use. There are also reports of symptoms in adults receiving treatment for approved and unapproved purposes. Although it is not FDA approved for any urologic indication, botulinum toxin is used off-label in the treatment for overactive bladder and, in research settings, for the treatment of BPH.

The different botulinum toxin products are not interchangeable, according to the revised label requirements, as the units used to measure the products vary. To reduce dosing errors, the products have changed their established (generic) drug names.

The products are: Botox (new established name: onabotulinumtoxinA), Botox Cosmetic (new established name: onabotulinumtoxinA), Myobloc (new established name: rimabotulinumtoxinB), and Dysport (abobotulinumtoxinA). Dysport, which was approved in April with a boxed warning, is not being asked to make name or label changes currently.

Brand names and formulations remain the same.