Countdown to Asthma Management

Vol. 19 •Issue 17 • Page 12
Countdown to Asthma Management

Dose counters on MDIs help asthmatics track medication use

The old floating-the-inhaler-in-the-water trick to measure how much medicine remained in an inhaler canister wasn’t necessarily a credible, scientific tool.

Actually, the technique is quite similar to the “Will It Float?” segment on the Late Show with David Letterman, in which the TV talk show host randomly selects items to emerge in a large tub of water to test their buoyancy. Using that method, Letterman discovered a regulation baseball bat floats; a brick of Velveeta cheese sinks.

Similarly, inhaler users—most likely at home, not a television studio—would drop the canister in a bowl of water that is as deep as the inhaler is long to estimate the amount of medicine inside.

If the canister sank all the way to the bottom, presumably it was filled. If it submerged entirely in the water with no part poking out, it was three-quarters full. If it poked half-way out of the water horizontally, it was half-full. If it tilted to the side out of the water, it was a quarter full. If it just lay on the surface, it was empty.

Although the rules of the float test were very specific, there are a number of problems with the technique, William Nadel, director of Market Development at Respirics Inc. in Raleigh, N.C., told ADVANCE.

“It’s all just sort of a guess,” he said. “It’s not a safe way to handle the drug. Water could get into the canister and interfere with the drug coming out of the inhaler.”

In 2002, researchers at the University of North Carolina at Chapel Hill investigated the float test’s accuracy using three asthma drugs: Atrovent, Flovent and Ventolin. They found floating characteristics varied depending on the medication, the canister’s design and the canister’s weight.

Since the float test proved inconsistent and unreliable, the UNC team concluded clinicians and asthma educators should not recommend it to patients. Thankfully, more credible methods of keeping track of canister medication are now the standard on pressurized metered-dose inhalers (pMDI).

FDA Steps In

Foremost, inhaler users could, when they suspect the canister is running low, simply toss it in the garbage and open a new one; but they would be potentially wasting medicine. Or they could chance it and keep using the inhaler, running the risk of there not being any medicine; but hedging their bet that way, they would potentially place themselves in harm’s way.

Aside from diligently keeping a log book of dosage use, a legitimate way for patients to know precisely the amount of medication left in the canister is a dose counter.

In fact, the U.S. Food and Drug Administration in 2003 printed a “Guidance to the Industry” for MDI product manufacturers, urging them to integrate dose-counting mechanisms in all their future product designs.

The FDA advised that all dose counters provide either a direct numeric count or color coding device, something that will provide “a clear indication of when an MDI is approaching the end of its recommended number of actuations as well as when it has reached or exceeded that number.”

When including dose counters on an MDI or a companion piece, the FDA recommends the counters:

  • Always be an integral part of the canister and/or actuator, even during cleaning, to avoid count corruption,
  • Provide a clear indication of when the device is approaching and has reached or exceeded the final dose,
  • Count downward,
  • Be designed to specifically avoid undercounting (for example, when the MDI sprays but the counter doesn’t advance),
  • Be engineered to track actuation reliably,
  • Be tested for ergonomics, ruggedness and accuracy in clinical settings (including use by pediatric and geriatric patient populations) and
  • Not lock out (for bronchodilators).

    Background Survey

    The FDA first implemented the guideline due in part to persuasion of the advocacy group Allergy & Asthma Network Mothers of Asthmatics (AANMA). Members of the AANMA requested the inclusion of dose counters on all inhalers and inhaler companion products as the result of a survey in which the organization uncovered some alarming statistics on inhaler use.

    Just how many asthma- and COPD-related hospitalizations, emergency visits, missed work and school days or deaths can be attributed to the use of empty inhalers is uncertain. In April 2003, the AANMA conducted a telephone survey of 500 non-member patients and parents of pediatric patients with asthma to talk about bronchodilator pMDI dose-counting issues.

    When asked to name the medication used when experiencing coughing, wheezing or shortness of breath, 52 percent of respondents named generic albuterol and 16 percent mentioned brand-name bronchodilators. Patients who named medications other than bronchodilators for the treatment of acute symptoms weren’t included, leaving 342 respondents.

    Of the people who mentioned bronchodilators, 36 percent said a medical professional had never advised them how to keep track of the number of inhaler doses used. Fifty-four percent refilled bronchodilator pMDI prescriptions more frequently than recommended by national guidelines. This may be because they were unsure whether they had exceeded the maximum number of doses.

    Thirty-two percent used the bronchodilator pMDI at least once daily. Twenty-five percent of respondents tried to use an empty inhaler when needed, resulting in 911 emergency calls for 8 percent. This was more likely to occur in patients reporting bronchodilator use more than once daily (35 percent) and in those diagnosed with asthma more than five years before the survey date (33 percent).

    Respondents agreed pMDIs should contain an integrated dose counter or indicator allowing patients to recognize visually when their pMDI may no longer effectively deliver medication.

    New to the Market

    In the time since the FDA issued the advisory, manufacturers, including Respirics, have followed suit. Its new inhaler companion product hit the market in June, featuring both an electronic dose counter and a breath-actuator, Nadel said.

    “Essentially, it has a numeric display and a little dial, a little graphic display that looks like a rainbow. As you use the device, every time you take a puff, it counts; and the lines on the gauge slowly disappear,” he said.

    The counter will display the number of the original amount of doses and the current number of doses. Albuterol, for example, contains 200 doses; so, after 25 puffs, the numeric readout will display “175” and one of the bars will disappear, he added.

    Dose counters for drugs like Flovent are not as essential as rescue drugs like albuterol, Nadel added.

    “Flovent is not that big of a deal because it works like an antibiotic. On the other hand, albuterol can be kept on hand for six months to a year at a time because it’s a rescue drug. The tracking function is more valuable in that case.”

    With the help of dose counters, clinicians can better manage the patient’s asthma and adjust their medication use accordingly.

    “The benefit there is you get to track how much medicine you’re using, and this, we hope, will minimize the risk of a patient trying to use an empty inhaler,” Nadel said. “The other side of that is you can actually track the number of doses you use. The device can extrapolate how much medication the patient has used.”

    As most asthma specialists know, getting their patients, especially children, to take their medications correctly is an ongoing challenge.

    Speaking at the annual meeting of the American Academy of Asthma, Allergy & Immunology in March in Miami Beach, Fla., Bruce Bender, MD, of the National Jewish Medical and Research Center in Denver reported very few children take the proper amount of medication prescribed to them. His team observed adherence of 131 asthmatic children throughout four months, finding that one in four used less than a quarter of the medication they needed, and 58 percent used less than half.

    With medication compliance in mind, dose counters may help kids and patients of all ages follow the proper adherence.


    Nancy Sander and Marissa Magnetti, MPA, contributed to this article. The full text of their feature story on dose counters titled “Running on Empty: Dose Counters for pMDIs Effectively Monitor Canister Contents” appeared in the March issue of ADVANCE for Managers of Respiratory Care.

    Sander is the founder of the Allergy & Asthma Network Mothers of Asthmatics of Fairfax, Va. Magnetti serves as the AANMA’s research and development project manager.

    You can reach Stacey Miller at [email protected]

    Symptom-Based Asthma Plans Cut Kids’ Trips to ER

    Children with asthma generally keep tabs on their asthma symptoms one of two ways–writing their symptoms daily in a log or measuring their lung function via a peak-flow monitor. When it comes to preventing trips to the emergency room, the former is more effective than the latter, authors of a new study discovered.

    Researchers at the Children’s Hospital of Eastern Ontario in Canada found that children whose asthma symptoms were tracked daily with a written plan reduced trips to the emergency department by 27 percent compared to children whose asthma plans are based on peak flow meters.

    “It is our theory that children using the symptom-based plan will use it more often if it (is effective in getting them) to control asthma by taking preventive medicine,” said Roger Zemek, author of the study, which appeared in the July edition of the Cochran Library.

    Surprisingly, researchers did not find any difference in the number of missed days of school, missed work time for the parents or hospital admissions between the two groups, which included a total of 355 children.

    Not only did symptom-based plans prevent fewer trips to the ER, but children preferred them compared to using peak flows, Zemek said.

    “Research outside of this review has shown that children do not have difficulty using peak-flow monitors and they have been found not to measure accurately the true inflammation. Using the symptom-based plan requires less of a time constraint on children and families, in addition to providing a medical benefit,” Zemek said.

    Kids who followed the peak-flow plans, however, reported asthma symptoms fewer days a week. This finding surprised Zemek because “that was the opposite direction of the primary outcome that children using symptom-based plans had fewer acute care visits.”

    Zemek’s team concluded that cut-off values used for the peak-flow plans might be more conservative than the symptom-based plans; so, children might seek medical attention sooner when they follow peak-flow based plans.

    “The reason why their main finding is key is that a vast chunk of health care spending is actually for acute care health care use such as going to the doctor and emergency department visits,” Jerry Krishnan, MD, of Johns Hopkins School of Medicine, said of the study.

    Krishnan warned, however, that asthma action plans don’t work for every child or patient, especially those who may have difficulty reading and writing.

    “If you impose a challenging action plan that involves multiple steps and decisions, that’s going to make it difficult to use. We need to make written action plans more user-friendly and easy to understand,” he said.

    –By Stacey Miller