Health Canada is warning consumers not to use patches containing powerful chronic pain drug fentanyl because they pose an overdose risk.

The manufacturer has voluntarily recalled the patches because they may have a tear along one side of the patch which could result in a leak of the potent gel. Direct contact with the leaked fentanyl gel could result in a potentially fatal overdose.

The patches are generally prescribed to treat chronic pain in people accustomed to narcotics.

The recall includes 25 mcg/hr Duragesic patches sold by Janssen-Ortho Inc. and 25 mcg/hr Ran Fentanyl Transdermal System Patches sold by Ranbaxy Laboratories Ltd. All the recalled drugs have expiration dates on or before December 2009.

Damaged patches should be returned to pharmacy for safe disposal and should not be handled directly, Health Canada said.

Skin that has been exposed to the gel should be rinsed with water but not washed with soap or alcohol.

Signs of fentanyl overdose include difficult or shallow breathing, tiredness, extreme sleepiness or sedation, inability to think, talk or walk normally and feeling faint, dizzy or confused. Anyone experiencing these symptoms should seek medical attention immediately.

The patches were also recalled in the United States, where they were sold under the brand name Duragesic by PriCara and generically by Sandoz Inc.