OTTAWA - A recall of a drug used to treat critically ill patients has prompted some Canadian health authorities to begin rationing it for only the most serious cases.

Sodium bicarbonate is used to combat buildup of acid in the blood, in open heart surgery, as an antidote to certain poisons, in cases of organ failure, and in some types of cancer chemotherapy.

Officials with Alberta Health Services say the province had about a six-to-seven-week supply of injectable sodium bicarbonate when the manufacturer, Pfizer, told them on June 8 about a shortage.

Late this week, the company announced it was recalling two lots of vials of the drug due to the potential for microbial contamination, reducing the Alberta supply to just six to seven days.

The global supply of the vials has been tight since late May due to manufacturing delays and Health Canada says the recall means that there is now a shortage in Canada and around the world.

Health Canada says it is working closely with the company, the provinces and territories as well as other partners and stakeholders to reduce the impact of the shortage on Canadian patients.