The toxin in Botox products may spread to distant parts of the body, with potentially fatal consequences, Health Canada said Tuesday in announcing new labelling information for the drugs.

Last February, the U.S. Food and Drug Administration said the toxin had spread, both in products the agency approved and those that were not. Health Canada has been reviewing the safety of Botox and Botox Cosmetic.

No medically confirmed cases of the toxin having spread have been reported in Canada.

In its advisory, Health Canada said the symptoms of "distant toxin spread" include:

  • Muscle weakness.
  • Difficulties swallowing.
  • Pneumonia.
  • Speech disorders.
  • Breathing problems.

Botox, made by Allergan Inc. of Irvine, Calif., is approved for treating muscle spasms in the neck, eye and foot, muscle pain and excessive sweating in Canada. Botox Cosmetic, which is made by the same company, is approved to treat facial wrinkling.

The drugs use botulinum toxin, which blocks nerve impulses to muscles, causing them to relax.

People with a history of neurological disorders, swallowing difficulties or breathing problems should be extremely cautious about using the products, Health Canada said.

When the U.S. issued its warning, the FDA said the deaths were all among children. Most had cerebral palsy and were being treated for limb spasms, which is not an approved use for the drugs in the U.S. or Canada.

The chances of death are remote because most applications don't require high doses, said Dr. Greg Storwick, a dermatologist in Calgary who injects clients with Botox every day.

But the growing popularity and high price of the treatment could result in it getting into the hands of people who aren't certified to inject it, he said.

"We have to remember that Botox is the most potent toxin known to man. Done improperly or abused, yes, there is potential for danger for it. Yes, it is potentially fatal.… But I think the government has to step in and start regulating who is allowed to use Botox and under what situations."

Health Canada has worked with Allergan to revise the labelling and will continue to monitor the safety of Botox products, the department said.