Health Canada is reviewing safety information on the wrinkle treatment Botox, just days after a call from a U.S. lobby group to increase the warnings on the drug.

Last week, Dr. Sidney Wolfe of Public Citizen Health Research Group said severe reactions including deaths have been linked to Botox.

Botox uses botulinum toxin, which blocks nerve impulses to muscles, causing them to relax. But in a few cases, the toxin has spread to other parts of the body, resulting in problems including paralysis of respiratory muscles and difficulty swallowing, potentially leading to food or liquids entering the lungs and causing aspiration pneumonia, Wolfe said.

Botox is traditionally used as a cosmetic treatment to ease facial wrinkles, but is also used for treating spasticity and tense muscles.

A Health Canada official said earlier Thursday that it was reviewing safety information for both Botox and a similar drug, Myobloc.

Myobloc also uses botulinum toxin to treat rigid neck muscles, a condition known as cervical dystonia. But the official said later Thursday that in fact Health Canada was reviewing just Botox, as Myobloc is not available in Canada.

The company that makes Botox disputed claims that complications from Botox cosmetic treatments have resulted in serious problems.

Allergan Canada said in a news release issued Wednesday that in the 18 years since the product was first approved worldwide, "reports of serious adverse events following Botox injection have been rare, and there has never been a single reported death where a causal link to Botox Cosmetic was established."

Health Canada spokesman Paul Duchesne told CBC News the review was triggered by "communications in Europe on the issues" surrounding the drug. He said the department will review international studies on Botox's safety.

Canadian officials say that if the review identifies any new safety information, it will be made public.

With files from the Associated Press