TORONTO — Slow-release painkillers known as opioids and any amount of alcohol could be a fatal combination, Health Canada warned Wednesday.

It urged people on the pain medications to avoid alcoholic drinks and over-the-counter medicines containing alcohol until further safety data can be gathered.

The concern was raised in relation to a drug known as Palladone XL, but may pertain to other similar slow-release pain drugs, the department said in a release Wednesday.

Product labelling for these types of painkillers already warns of the dangers of combining them with alcohol. But the new information on Palladone XL underscores the importance of observing that warning, department spokesperson Jirina Vlk said.

"We're investigating whether the slow-release mechanism of other opioids might also be affected,'' Vlk said from Ottawa.

"But at this time, the warning should be heeded that no alcohol should be combined with this medication, as it may result in an immediate release of a fatal dose of the drug.''

Health Canada has asked makers of similar drugs to provide data on their products' interaction with alcohol. If the companies don't have such data, the department has instructed them to conduct studies on the possible interaction and submit the data within six months.

The advisory was prompted by information provided by Purdue Pharma, the maker of Palladone XL. Last month the U.S. Food and Drug Administration told Purdue Pharma to withdraw the drug from the U.S. market based on the information, which suggested people who consumed alcohol while taking the slow-release pain medication could suffer serious, even fatal reactions.

Health Canada has ascertained that Purdue Pharma has not shipped any Palladone XL to Canada since December and that there are no supplies of the drug on the Canadian market, the release stated.

There have been no reports in Canada of serious side-effects related to use of the drug.

"This safety issue may be limited to Palladone XL, but patients using other slow-release opioid products should be aware that there may be a possibility that these products could react in the same way when taken with alcohol,'' Health Canada warned.

Palladone XL capsules contain a slow-release form of a medication called hydromorphone. But alcohol can override the slow-release format of the drug, disbursing potentially dangerous levels of hydromorphone quickly into the blood stream rather than over a 24-hour period -- an effect known as dose dumping.

Slow-release medications may also be described as extended release, controlled release and controlled delivery. They may also carry such abbreviations as SR, XR, XL, SRC and SRT.

Other slow-release opioids sold in Canada include: Hydromorph Contin (hydromorphone); Kadian SRC (morphine sulfate); M.O.S. SR (morphine hydrochloride); M-Elson (morphine sulfate); MS Contin SRT (morphine sulfate); Oxycontin SRT (oxycodone); PMS-Morphine Sulfate SR (morphine sulfate); Ratio-Morphine SR (morphine sulfate); Roxanol SR (morphine sulfate); and Zomorph (morphine sulfate).