• Decrease font size
  • Return font size to normal
  • Increase font size
U.S. Department of Health and Human Services


  • Print
  • Share
  • E-mail

Follow-up to the February 8, 2008, Early Communication about an Ongoing Safety Review of Botox and Botox Cosmetic (Botulinum toxin Type A) and Myobloc (Botulinum toxin Type B)


Please see current information: Update of Safety Review of OnabotulinumtoxinA (marketed as Botox/Botox Cosmetic), AbobotulinumtoxinA (marketed as Dysport) and RimabotulinumtoxinB (marketed as Myobloc)

[4/2009] This information reflects FDA’s current analysis of available data concerning these drugs.

As the result of an ongoing safety review, FDA has notified the manufacturers of licensed botulinum toxin products of the need to strengthen warnings in product labeling, and add a boxed warning, regarding the risk of adverse events when the effects of the toxin spread beyond the site where it was injected. 

FDA also has notified the manufacturers that development and implementation of a Risk Evaluation and Mitigation Strategy (REMS) is necessary to ensure that the benefits of the product outweigh the risks.  The REMS would include a Communication Plan to provide more information regarding the risk for distant spread of botulinum toxin effects after local injection, as well as information to explain that botulinum toxin products cannot be interchanged.  The REMS would also include a Medication Guide that explains the risks to patients, their families, and caregivers. 

In addition, FDA is requiring the manufacturers to submit safety data after multiple administrations of the product in a specified number of children and adults with spasticity to assess the signal of serious risk regarding distant spread of toxin effects. 

Botulinum toxin products have been approved by FDA for one or more of the following uses:  temporary improvement in the appearance of glabellar lines (frown lines between the eyebrows), treatment of strabismus (crossed eyes), blepharospasm (abnormal tics and twitches of the eyelids), cervical dystonia (involuntary sustained or repetitive contraction of the neck muscles), and primary axillary hyperhidrosis (severe underarm sweating).  For these uses, botulinum toxin is injected into the skin or into muscle tissue.

Postmarketing Review

The following information summarizes FDA’s review of postmarketing safety data obtained from the manufacturers of botulinum toxin products, and all existing data within the Agency regarding these adverse events:

In pediatric postmarketing adverse event case reports, botulinum toxin products were mostly used to treat muscle spasticity in cerebral palsy, a use that has not been approved by the FDA. The reported cases of spread of botulinum toxin effect beyond the site of injection were described as botulism, or involved symptoms including difficulty breathing, difficulty swallowing, muscular weakness, drooping eyelids, constipation, aspiration pneumonia, speech disorder, facial drooping, double vision, or respiratory depression.  Serious case reports described hospitalizations involving ventilatory support and reports of death. 

The majority of the adult postmarketing case reports of distant spread of toxin effects occurred following use of botulinum toxin for the treatment of spasticity (an unapproved use) or cervical dystonia.  Some cases resulted in hospitalization, including several cases that required placement of a gastric tube or mechanical ventilation.  Although there were several deaths in adults, it is not possible to attribute them to the botulinum toxin because the patients also suffered from complications of their pre-existing conditions.  In addition, there have been reports where some symptoms could be consistent with distant spread of toxin effect following dermatologic use.  However, no definitive serious adverse event reports of distant spread of toxin effect associated with dermatologic use of Botox at the labeled dose of 20 Units (for glabellar lines) or 100 Units (for severe primary axillary hyperhidrosis) have been identified. 


FDA’s evaluation of the data continues to support the recommendations made in the 2008 Early Communication; that healthcare professionals who use botulinum toxin products should:

  • Understand that dosage strength (potency) expressed in “Units” or “U” are different among the botulinum toxin products; clinical doses expressed in units are not interchangeable from one botulinum toxin product to another.
  • Be alert to and educate patients and caregivers about potential adverse events due to distant spread of botulinum toxin effects following local injections including: unexpected loss of strength or muscle weakness, hoarseness or trouble talking (dysphonia), trouble saying words clearly (dysarthria), loss of bladder control, trouble breathing, trouble swallowing, double vision, blurred vision and drooping eyelids.
  • Understand that these adverse events have been reported as early as several hours and as late as several weeks after treatment.
  • Advise patients to seek immediate medical attention if they develop any of these symptoms.

FDA Response to Citizen Petition


Adverse reactions or quality problems experienced with the use of this Product may be reported to the FDA's MedWatch Adverse Event Reporting program either online, by regular mail or by fax, using the contact information at the bottom of this sheet.


Contact FDA

1-800-FDA-0178 Fax
Report a Serious Problem

MedWatch Online

Regular Mail: Use postage-paid FDA Form 3500

Mail to: MedWatch 5600 Fishers Lane

Rockville, MD 20857