Health Canada has approved the anti-wrinkle treatment Botox for people who suffer with chronic migraines at least 15 days a month.

Botox, or onabotulinumtoxinA, can now be used as a preventive treatment for adults who have headaches that last fours hours a day or more for half a month, maker Allergan, Inc. announced Monday.

Botox, best known for its cosmetic uses, is also approved in Canada for preventing chronic migraines and to treat muscle stiffness and spasticity. Damian Dovarganes/Associated Press

Health Canada's approval was based on clinical trial data involving 1,384 adults collected by the drug's maker.

In the clinical trial, those treated with Botox experienced fewer headache days and less time with headaches compared with those taking placebo, the company said.

Adverse reactions reported by more than two per cent of patients treated with the drug and more frequently than in patients treated with placebo included:

• Eyelid drooping.
• Pain at the injection site.
• Sinusitis.
• Bronchitis.
• Neck pain.
• Musculoskeletal stiffness or pain.
• Muscular weakness.
• Myalgia (muscle pain).
• Headache.
• Migraine.
• Loss of facial muscle motor function or facial paresis.

Botox is made from a neurotoxic protein that in large doses can cause the paralytic illness botulism.

It is also authorized in Canada for non-cosmetic purposes to treat spasticity in muscles and muscle stiffness, and to decrease muscular responsiveness. It is best known for its cosmetic uses, such as its ability to counter the appearance of moderate to severe frown lines between the eyebrows and around the eyes.

In 2009, Health Canada announced new labelling information for the drug to indicate the toxin in Botox products may spread to distant parts of the body.