The Food & Drug Administration (FDA) has announced that Botox, Botox Cosmetic and Myobloc have been linked to serious adverse reactions when used in a variety of dosages to treat a number of different conditions.In its public statement, the FDA listed respiratory failure and death among the reported side effects, but also said those reactions “may be related to overdosing.”

Botox and Myobloc are types of botulism toxins, and Botox Cosmetic is best known for temporarily improving the appearances of wrinkles such as “frown lines.” But Botox and Myobloc have also been approved to treat certain types of muscle spasms and muscle contractions.

“FDA is aware of the body of literature describing the use of botulinum toxins to treat limb spasticity in children and adults,” the news release said. “The safety, efficacy and dosage of botulinum toxins have not been established for the treatment of limb spasticity of cerebral palsy or for use in any condition in children less than 12 years of age.”

The serious side effects seem to result, the FDA reported, when the toxins spread beyond their original injection sites: “The most serious cases had outcomes that included hospitalization and death, and occurred mostly in children treated for cerebral palsy-associated limb spasticity.” The FDA said such use is not approved in the United States. Side effects have been noted as soon as the day after an injection and up to several weeks post-injection, the FDA said.