Asthma inhaler running out? Hard to tell

NEW YORK — Because asthma inhalers do not include dose counters, asthma sufferers may unknowingly run out of their rescue medication, experts warn in a new report. They call for manufacturers of pressurized metered-dose inhalers, or pMDIs, to include dose counters as a standard feature.

These devices are the cornerstone of asthma treatment. They contain a specified number of doses of medication. But after an asthma sufferer has used up the potentially lifesaving medication, pMDI canisters may continue to deliver 20 to 80 percent more puffs containing little more than inactive propellant.

How do patients know when their pMDI is empty or when it’s time to refill their inhaler prescription? Nancy Sander, founder and president of the Allergy and Asthma Network Mothers of Asthmatics in Fairfax, Virginia and colleagues surveyed 500 US families with asthma to find out.

They report that 87 of 342 respondents (25 percent) who said they used a bronchodilator for relief of an asthma attack reported having found their pMDI empty during one of these attacks. Seven of these patients had to call 911 as a result.

Seventy-one of these 87 asthma patients (82 percent) wrongly thought that they could tell when their asthma inhaler was empty when absolutely nothing came out of it.

The survey team also found that only 36 percent of pMDI users reported ever having been told by their doctor to keep track of doses they used. This is an “alarming finding,” study co-author Dr. Bradley E. Chipps, of Capital Allergy and Respiratory Disease Center in Sacramento, California, said in a statement.

Even if more had been told, “without an integrated dose counter, there is no reliable way for patients to track medication usage,” Chipps said.

The methods people with asthma currently use to determine whether medication remains in the pMDI are all “faulty,” said Sander.

These include maintaining a diary, which is “wholly impractical” as pMDIs are used on an intermittent basis. Only 8 percent of those surveyed used this method.

Spray testing — the most common method of testing pMDIs — is totally ineffective because propellant remains in the device after the medication is used up, as mentioned.

There is no solid evidence to support the reliability of the float test — floating the canister in water and noting its position to determine if medication is left inside. Although advocated in the past, many pMDI manufacturers now advise against immersing or floating the canister.

The survey results appear in the July issue of Annals of Allergy, Asthma & Immunology. In a commentary, Dr. John Oppenheimer supports the authors’ conclusion that manufacturers of inhaled medicines should include dose counters as a standard feature on multidose inhalers. [

Without dose counters, patients are left to wonder whether their inhaler is “running on empty,” writes Oppenheimer from the University of Medicine and Dentistry of New Jersey.

Recently, the US Food and Drug Administration advised pMDI manufacturers to include dose counters in the future. The first pMDI with a dose counter was introduced this month and others are not far behind, Sander said. “We hope these advances will help reduce emergency department visits, hospitalizations, missed school and work days and death due to empty inhalers,” she added.

SOURCE: Annals of Allergy, Asthma & Immunology, July 2006.

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