Health Canada has asked the makers of a herbal sleep aid to recall its product after finding a substance they say poses “serious health risks.”

The Canadian agency says after testing several U-Dream and U-Dream Full Night herbal sleep-aid products it found a substance similar to the prescription drug zopiclone, which is used to treat insomnia.

Health Canada said it tested the products after receiving complaints of unusual side effects, such as symptoms of withdrawl and dependence, suggesting that the product may contain a substance not listed on the label.

The side effects of zopiclone include of drowsiness, dizziness, memory loss, hallucinations and abnormal sleep behaviours while not fully awake.

“Zopiclone use may lead to dependence or abuse, and stopping the drug abruptly may cause withdrawal symptoms, including convulsions, tremor, muscle cramps, vomiting, sweating, hallucinations and difficulty sleeping,” Health Canada said in an advisory issued Dec. 23. “In addition, zopiclone should not be used by pregnant or nursing women, children, or patients with breathing difficulties.”

Health Canada has suspended the product licenses for U-Dream and U-Dreams, making it illegal for anyone to sell the product in Canada. A full list of the products included in the suspension is located below.

Biotrade Canada Ltd., says U-Dream Lite and U-Dream Full Night are the only products it has been marketing in Canada.

The Health Canada recall comes on the heels of the U.S. Food and Drug Administration advising consumers not to purchase or use U-Dream Full Night after it detected the hidden ingredient zopiclone, which has not been approved for use in the United States.