Eearly in the spring of last year, I suddenly found that the easy jaunt up the three stories to my condo had turned into a frightening ordeal. After getting up the stairs, I had to sit down for several minutes to catch my breath. I couldn’t even make it through my usual Sunday stroll around the local reservoir without taking a break.

My doctor’s diagnosis: My asthma, which had been in check for years, had intensified. The rescue inhaler I had been using to provide relief for occasional wheezing was no longer sufficient.

He prescribed a maintenance inhaler to reduce the likelihood of asthma flare-ups. The inhaler works only if it is faithfully used every day. And sure enough, after three weeks, the stairs no longer seemed as daunting as Mount Everest.

But something else was now taking my breath away: the cost of that maintenance inhaler. I happened to glance at one of the “Statement of Benefit” notices my insurer sends after a claim, correspondence I typically consign to the junk mail pile. The notice listed the full cost of my asthma inhaler at $325 — about as much as a 40-inch LED television. Since a single inhaler lasts just one month, I calculated that a year’s supply would come to $4,000. Fortunately, as I’ll explain later, my copay was just a fraction of that amount.

That drug companies can command such high prices for potentially lifesaving medication is under new scrutiny following a spike in the cost of EpiPens, injection devices used to reverse severe allergic reactions to bee stings, peanuts, and other allergens.

I had first used maintenance inhalers in the early 1980s, when I got my diagnosis of asthma. I was surprised to find that three decades later, there was still no generic version. After all, the active ingredients — steroids — are hardly exotic. It’s what happens to them in the laboratory that keeps generics off the market.

“The original drug may go back decades,” said John Fahy, director of the Airway Clinical Research Center at the University of California at San Francisco. But if pharmaceutical companies “tweak the formulation, they can get a patent extension.”

“Delivery devices, formulation changes, modifying the drugs so they last longer — there’s been a lot of that activity in the last 20 years,” he continued. “But the core three ingredients in the inhalers have not changed.”

One of those changes came about within the last decade — at the behest of the federal government.

Remember the ozone layer scare back in 1980s? Huge gaps were opening in that critical atmospheric layer that protects us from skin cancer-causing ultraviolet radiation.

The culprit was chlorofluorocarbons (CFC), chemicals compound commonly found in air conditioners, refrigerators, and aerosol sprays. Under the Montreal Protocol, which entered into force in 1989, the world’s leading countries agreed to phase them out.

The compound also served as a propellant in asthma inhalers, but their use accounted for just one-tenth of one percent of CFCs emitted into the atmosphere. Still, the Food and Drug Administration announced in the late 1990s that it was considering banning CFC inhalers once the pharmaceutical industry came up with alternatives.

Erik R. Swenson, a pulmonary care specialist with the Veterans Administration and a professor at the University of Washington, sat on one of the FDA’s advisory panels on the inhaler question.

Swenson recalled that environmental experts said the ozone layer would repair itself in 50 years if CFCs were eliminated. When he asked them how much longer it would take if the CFCs in asthma inhalers were exempted, he recalled the answer as “roughly another week.”

Patient advocates focused their attention on a generic relief inhaler with the active ingredient albuterol that sold for $15 or less. They warned that if the inhalers were reformulated to replace CFCs, the generic version would be banned.

Their fears were realized after the pharmaceutical industry developed a substitute propellant, HFA (hydrofluoroalkane).

The FDA concluded that it wasn’t in a position to judge how perilous inhalers were to the ozone layer. It forced the generic inhalers off the market at the end of 2008.

In a document accompanying the ruling, the agency quoted a projection from an economic consultant who had been hired by the pharmaceutical giant GlaxoSmithKline: The reformulated rescue inhaler would increase the average cost per patient by just $16 a year.

That projection turned out to be optimistic. The average annual cost per individual using the albuterol inhalers rose to $208, a $71 increase, according to government estimates. That amount includes what was paid both out of pocket and by insurers.

Nationwide, total annual expenditures on albuterol increased to $1.6 billion, up from $984 million. That’s an increase of more than 60 percent, only a small part of which can be explained by the 10 percent rise in the number of people using inhalers.

These figures are based on a comparison between the average annual expenditures for the four years leading up to the ban (2004 to 2008) and those for the four years following the ban (2009 to 2013). To account for inflation, the numbers were adjusted to 2013 dollars. (They were compiled by the Agency for Healthcare Research and Quality, a division of the Department of Health and Human Services, using the household component of its annual Medical Expenditures Panel Survey.)

But the actual cost of the CFC ban may be billions of dollars more. Maintenance inhalers had also relied on CFCs. The switch to the HFA propellant “put a roadblock” in the way of a generic version of maintenance inhalers, Fahy said.

“This resulted in new formulations with new patents, but it did not result in major new treatment advances for patients,” he said. “Although seven new inhaled drugs have been approved for asthma over the last five years, none of these drugs target new disease pathways in the lungs.”

Medicare alone spent $4.1 billion to cover the cost of the major brands of maintenance inhalers in 2014, the latest year for which figures are available. For the same year, Medicare spent $680 million on albuterol-based relief inhalers. And the Medicare population, largely composed of people 65 and over, accounts for only 7 percent of the 25 million Americans who suffer from asthma, according to the Centers for Disease Control and Prevention.

Prominent brands of steroid inhalers include Pulmicort, Qvar, Flovent and Asmanex. They differ in delivery systems (spray or powder) and in their formulation. However, their active ingredients are steroids that have been on the market since at least the 1970s.

Following the CFC ban, the pharmaceutical industry came under fire for capitalizing on the ozone scare.

In an email, Maureen Donahue Hardwick, legal counsel for the International Pharmaceutical Aerosol Consortium, vehemently denied this charge. “IPAC’s member companies did not [her emphasis] proactively seek a phase out of CFCs,” she wrote, “and did not view this as some sort of commercial opportunity. Rather, the companies responded to the strong global concern … on the significant negative impacts to the ozone layer caused by CFCs and other ozone-depleting substances.”

While the ban on generic albuterol inhalers generated press attention at the time, and while the news media have occasionally called attention to the problem (notably in this front-page article by Elisabeth Rosenthal in The New York Times), there has been no widespread public outcry about the high cost of inhalers — even though asthma afflicts 1 in 11 children and 1 in 12 adults.

In large part, that’s because private or public insurance picks up most of the cost, and the size of copays does not necessarily correspond to the differences in the actual cost of prescriptions.

To find out what I’d pay without insurance, I checked the prices of two common inhalers on the drug-comparison website goodrx.com. The lowest price for a 120-dose Flovent HFA (220 mcg) inhaler, which is for maintenance use, was $337; for a 200-dose Ventolin HFA (90 mcg) inhaler, which is for immediate relief, the price was $58. (In Canada, the prices were $100 and $30, respectively.)

However, my out-of-pocket expense for each inhaler is the same: $16.67 (I buy them in bulk, at three for $50).

Who makes up the rest of the cost? Well, we all do, through higher premiums and taxes.

The soonest we may see a generic inhaler is next year, when several companies plan to come out with versions of the maintenance drug Advair. There’s no word on when albuterol, the rescue medicine, will be available again as a generic inhaler.

Producing generic versions of inhalers is much more complicated than making generic pills. Each inhaler is protected by multiple patents, which expire at different times and cover such components as the chemical formula and the delivery system. A patent lasts 20 years from the date it is filed.

Dr. Christopher Hardy Fanta, a Harvard professor who is director of Partners Asthma Center in Boston, reflected the frustration of asthma specialists interviewed for this story.

“The bee in my bonnet is that these inhaled steroids have been available since the mid to late 60s, and here we are 50 years later and there is no low-cost, generic steroid inhaler on the market,” he said. “And it seems like a crime.”

Steve Maas is a freelance journalist and former Boston Globe editor who lives in Brookline, Massachusetts.