Doctors like the new inhalers that the government is requiring people with asthma and allergies to begin using tomorrow, but the transition may cause problems for some patients, according to Dr. Deborah Gentile, director of research of allergy and asthma at Allegheny General Hospital.

Albuterol will remain "the medicine that opens up the airways so you can breathe," Dr. Gentile said. What is changing is the propellant: Instead of chlorofluorocarbons, or CFCs, which have been linked to depletion of ozone in the earth's atmosphere, the new propellant will be hydrofluoroalkane, or HFA, which doesn't harm the ozone.

"We actually get much better delivery with the new propellant," Dr. Gentile said. "More of it gets to your lungs."

Still, there will be some problems for some patients.

In the first place, the new inhalers, to which many insurance companies have already switched subscribers, are only available in brand-name form (ProAir, Proventil, Ventolin and Xopenex). That means patients will pay more than they did for generic versions of the old CFCs-propelled inhalers.

"For most people with insurance, I figure the price will go from a $10 co-pay to a $30 co-pay," Dr. Gentile said. "Someone without insurance could end up paying $60 to $90 out of pocket."

Even though patients should use the "rescue medicine" at the rate of no more than one to two canisters a year, "there are going to be people who can't afford the drug," Dr. Gentile said.

She noted, though, that the drug companies have made available samples and vouchers for free inhalers, "and some companies may knock down the co-pay or give the drug for free just to help with the transition."

In the second place, doctors are worried that because the "blast of air" delivered by the two propellants differ, patients may accidentally overdose on the new inhalers.

"Technically, with the old propellant, you had a cold blast that would hit the back of your throat. The newer one is gentler and not cold," Dr. Gentile said. "They may think they're not getting the medicine and take more than they need."

If they do take too much, the doctor said, "they could have increased heart rate, tremors, headaches and vomiting -- like a caffeine overload."

Finally, doctors worry that the switch will confuse some patients.

"We've been trying to be proactive and get the word out as people call in for prescriptions for refills," Dr. Gentile said. "But some just aren't savvy and get confused. The last thing that you want is for them to be using the old one at the same time as the new one. Again, it's the overdose thing."