Updated

Hundreds of thousands of asthma sufferers who use an over-the-counter inhaler will be compelled to seek a more costly prescription device by the end of the year, when the federal government plans to ban them over environmental concerns.

The Food and Drug Administration last week began a media push to get the word out about the looming phase-out. After Dec. 31, the epinephrine asthma inhaler known as Primatene Mist will no longer be available.

The product is currently the only FDA-approved over-the-counter inhaler and is being taken off the shelves because it uses something called chlorofluorocarbons (CFCs) as a propellant -- the substance is considered harmful to the ozone layer.

The FDA push to regulate the chemical in inhalers has been under way since 2006. And it stems from an international treaty signed under the Reagan administration.

But with the clock ticking, the phase-out has raised concerns. The FDA estimates about 2 million people use Primatene Mist. Identifying them is difficult since users would have bought the product without a prescription. And the FDA acknowledges that many patients may have bought this particular brand because they have no health insurance.

"This has been a challenge," FDA spokeswoman Karen Riley told FoxNews.com.

Users of the product unaware of the change could be scrambling to find their favorite brand. Arthur Abramson, who launched a group opposed to the phase-out several years ago, said some people will end up finding out they need a prescription "in the middle of an asthma attack."

Abramson, though, said the entire phase-out is unnecessary. He said that at their peak about 15 years ago, CFC inhaler emissions accounted for less than 1 percent of global CFC emissions.

"They contribute next to nothing," Abramson said. "This thing was simply done for symbolic reasons."

In lieu of Primatene Mist, the FDA has suggested users of the product get a prescription for sanctioned inhalers, such as those that use an "environmentally friendly" propellant known as HFA.

But Abramson said thousands of people swear by the Primatene Mist inhalers, and he described the HFA-based inhalers as inferior.

"They should have the right to have it, and now they don't," he said.

Abramson launched The National Campaign to Save CFC Asthma Inhalers, an informal group he said will soon seek nonprofit status, in 2007. An asthma sufferer himself, he said his group has gathered thousands of names on its petition against the change -- he conceded the rule change is going forward regardless of opposition, at least until the next election.

Riley said the FDA, which finalized the rule in late 2008, is doing its best to inform people about the change.

On a conference call last week, one FDA official noted that patients using the $18 Primatene Mist inhalers might have to seek prescriptions for products that cost about $45. But Riley said these costs would be covered by Medicare and Medicaid for those who fall under those programs.

Andrea Leonard-Segal, with the FDA's Center for Drug Evaluation and Research, said on the call that some companies might have patient assistance programs to make products available at a reduced price.

Badrul Chowdhury, also with the center, said most countries have already done away with CFC-based products.

"This is being done gradually, keeping a very clear eye to the patient's health," Chowdhury said.

This isn't the last product to be phased out. Chowdhury said a prescription inhaler using Pirbuterol will be phased out at the end of 2013, as will another prescription product known as Combivent.

A representative with the company that manufactures Primatene Mist, Amphastar, could not be reached for comment.

Norman Edelman, chief medical officer with the American Lung Association, said his group is supportive of the phase-out. He said that an upside of the change is it will encourage people who only use Primatene Mist to consult a physician about more comprehensive medication.

"There are lots of substitutes," he said.