TORONTO -- Repeated shortages of the life-saving EpiPen has "moved from an inconvenience to a concern," says Food Allergy Canada.

The national advocacy group was among those alarmed by yet another announcement from Pfizer that its epinephrine auto-injector is in short supply, with executive director Jennifer Gerdts saying the latest shortfall comes just when it's needed most.

"The month of August ... is a key peak demand time for our audience given that it's back-to-school," says Gerdts, noting that many schools request students have an extra EpiPen onsite as a backup.

"This is the time at which they are looking to refill prescriptions."

The drug giant said Monday that it expects its EpiPen auto-injector will be in "very limited" supply in Canadian pharmacies in August, and that new stock likely won't be available until the end of that month.

The EpiPen auto-injector delivers 0.3 mg of epinephrine and is intended for those who weigh 30 kilograms or more (approximately 66 pounds or more).

That could include patients as young as eight or nine years old, especially since most allergists graduate young patients from the EpiPen Jr -- which delivers 0.15 mg epinephrine and is intended for children 15 to 30 kg (or 33 to 66 pounds) -- once they hit 25 kilograms, says Barrie, Ont., allergist David Fischer.

Fischer says there have been supply issues in Canada for most of 2018.

It's been so bad, he's heard of doctors discussing workarounds, such as letting patients have two EpiPen Jr's if the larger-dose injector is not available.

He adds that's not ideal, because the needle length is made for a child.

"It has happened from time to time," says Fischer, also president of the Canadian Society of Allergy and Clinical Immunology.

"No one has really looked into this as a viable alternative because normally it does not happen. Normally, it should not happen."

Supply is also currently low for the EpiPen Jr, but stocks are being managed across the country and Pfizer says it "continues to be available and allocated at a national level."

Fischer says that's in large part due to Health Canada's "preventative allocation approach," in which pharmacies have been instructed to be judicious about how many they dispense at a time.

Without that management, things could be much worse.

"The fact that there's (several) weeks without it is a crisis-of-a-kind but it's not the same as knowing there's not going to be anything for six months. Because of the careful shepherding of it, it actually has worked out better than it might have," he says.

But you can't shepherd what does not exist, he adds.

Although more EpiPens are expected in September, there were no assurances the supply would remain stable: "There will be stock in September for September. As for October, (we) don't know. It's a month-by-month basis ... and this is the way it's been all year. A lot shows up, we're in preventative allocation. If nothing shows up, we're in shortage."

Gerdts says it's already causing problems, and she expects it to worsen as the shortage makes its impact in coming weeks.

"We've had a few families contact us saying: 'We've gone to three or four pharmacies, we can't find the product,"' says Gerdts, noting that includes families in Atlantic Canada and Toronto.

"We're now at the point where we say: You know what? It's time to get some answers.... We need clarity on the root cause of the issue. What are the steps that are being taken and what's the time frame to resolution?"

Christina Antoniou, a spokeswoman for Pfizer Canada Inc., says the shortage is the result of "manufacturing delays."

"Stock that was scheduled to be shipped in early August is currently being inspected, which has caused a delay," she said by phone from Montreal.

EpiPen products expire on the last day of the month indicated on the package, so those with an August expiry date are good until Aug. 31.

Health Canada says anyone who has an anaphylactic reaction but has only an expired EpiPen should use the expired product and immediately call 911.

While those already managing allergies likely have recently expired EpiPens to use in a pinch, Fischer worried about newly prescribed patients who may have nothing.

There are no alternative auto-injectors available in Canada.

Jacalyn Duffin, a hematologist and medical historian who tracks drug shortages on her own website, CanadianDrugShortage.com, says the EpiPen shortage is "really serious" but is just one of dozens of medications in short supply.

She calls it "the tip of an iceberg."

"It's very frightening for the people that are affected but it's just part of a massive problem that we can't get to the bottom of until we understand the causes of all of it," says Duffin.

"We are just sort of lurching from one problem to another trying to put out the fires caused by individual shortages."

About 2.7 million Canadians have food allergies.