A key drug to treat chronic lung infections and tuberculosis is in short supply, leaving patients, doctors and pharmacies scrambling without success to try to refill prescriptions.

Carrie Chenier, 73, of Toronto has a chronic lung infection called Mycobacterium avium complex or a Mac attack that left her coughing up copious amounts of phlegm, forced her to sleep sitting up and limit her walks to five to 10 minutes.

"I just couldn't breathe," said Chenier, who previously had a heart valve operation.

The treatment is 18 months of a combination of several drugs and the main one of which is ethambutol. When she reached the 12-month mark, Chenier received a disturbing surprise.

"I went into the drug store and he said we can't get this," Chenier said Tuesday. "I said are you kidding? He said no. We may be able to get this in September but we don't think so."

Carrie Chenier

Carrie Chenier had trouble breathing for months until she started a combination of drugs. She's down to one week's supply of the key medication, Ethambutol. (Melanie Glanz/CBC)

The Canadian Drug Shortage Database lists tablets of Valeant Canada's Etibi. The reason for shortage is "Delay caused by the manufacturing site transfer"  — a change in location of where it is made in Canada.

It's not known how many people have infections like Chenier's, which damages and destroys lung tissue. In Ontario, it's about 10 times as common as tuberculosis, an infection that is also treated with ethambutol, said Dr. Ted Marras, a respirologist at Toronto Western Hospital.  

Every year about 1,600 cases of tuberculosis are reported in Canada.

Rationed for infectious TB patients

Both infectious TB patients and those like Chenier are in a difficult position.

"One option is that we can try to substitute another drug but we have no assurance that is going to work and it may cause other side-effects," Marras said.

The World Health Organization lists ethambutol on its essential medicines list. The UN public health agency defines essential medicines as those "intended to be available within the context of functioning health systems at all times in adequate amounts, in the appropriate dosage forms, with assured quality, and at a price the individual and the community can afford."

For the approximately 10 per cent of TB cases that are resistant, ethambutol is even more critical, Marras said.

"Toronto Western is stuck just like the pharmacies everywhere else. They haven't been able to locate any for non-TB cases."

For non-TB mycobacterial patients, their illness can worsen further and faster without ethambutol, he said. 

Valeant said to prevent stockpiling, it's rationing its supply and those who need the drug should be able to get it.

Chenier's pills are down to one week's supply. She continues to call her pharmacy and fears what could happen, not only for her but others just beginning their course of therapy.

"I'm worried that I'm going to go back to where I was. That's big time and you can't live like that. It's not life."

Health Canada said Valeant Canada has indicated a production shortage of ethambutol 100 mg tablets until August 2015 and ethambutol 400 mg tablets until September.

"All provinces and territories have been informed of this situation and they have not signaled any foreseen shortages to their supply of ethambutol," Health Canada said in an email response to questions.

"To date, there is no critical national shortage of ethambutol."

With files from CBC's Melanie Glanz