A recall of a "life-saving" drug used to treat critically ill patients has prompted some Canadian hospitals 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.

Locating alternative supply may be challenging in an international shortage. - Health Canada

Last week, the drug's maker, Pfizer, informed Health Canada it was recalling two lots of vials because because of possible microbial contamination.

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

The agency said it is working "to reduce the impact of the shortage on Canadian patients."

"We are gathering information about the supply situation and possible mitigation strategies, including alternative sources," it said in a statement Saturday. "Locating alternative supply may be challenging in an international shortage."

'A serious issue'

There are two injectable sodium bicarbonate drugs authorized in Canada, both supplied by Pfizer: vials and pre-filled syringes. The recall does not affect the pre-filled syringe format, and the company is allocating supply of these according to priority. It expects to ship more of them in late July or early August.

Until the supply issue is resolved, Pfizer has asked hospitals to restrict their use to life-saving procedures and critical emergencies only.

Alberta Health Services, which oversees health care for the entire province, said the recall has left it with only about a week's supply.

"For the patients that are more critically ill, it is really something that is life-saving and is used in critical care units," said Dr. Francois Belanger, chief medical officer for AHS. "The drug shortage is a serious issue and we are working hard to mitigate its effects."

AHS is currently managing its remaining stock by implementing an approval process to ensure the patients who need the drug most are getting it.

"Six to seven days is a best-guess estimate with respect to our stocks we have in reserve, but we anticipate in the next few days we'll have other strategies to alternate products or to other sources so we can drag that out a little bit longer," said Mauro Chies, vice-president of clinical support services.

"Six to seven days is kind of our worst-case scenario, but we think we can do better on that."

Chies said the province is looking for alternate sources in other countries.

AHS has even explored the idea of producing the drug itself, Belanger said, though he described that process as "complicated" and "not the first option."

Pfizer Canada informed Health Canada on June 14, 2017, that it was voluntarily recalling two lots of 8.4% sodium bicarbonate injection, USP, 50 mL vials, because of possible microbial contamination in the manufacturing process. (Pfizer)

Toronto's Sunnybrook hospital, which is the biggest trauma centre in the country, told CBC News it has not cancelled any procedures and is not experiencing a shortage.

And a spokesperson for the University Health Network, which is made up of four major hospitals in Toronto, said there is "no impact for now" because the hospitals have several weeks' supply, which they are conserving. A spokesperson for McGill University Health Centre in Montreal told CBC News the hospital is "concerned about the current limited supply" and is also tightly managing its stock.

Hospira, the division of Pfizer that makes the drugs, said in a statement on Thursday that the contamination in sodium bicarbonate and several other products was discovered during a "routine

simulation of the manufacturing process" which it said presented the potential for the introduction of micro-organisms into the products.

It said that no batches of distributed product have been found to actually contain micro-organisms, but that contamination remains a possibility.

Hospira said the affected lots were distributed in Canada, the U.S., including Puerto Rico, as well as the Dutch Antilles, Barbados, Philippines, Kuwait, and Singapore from January to June 2017.