Clinical Citations: Dose counting when using pressurized metered-dose inhalers: Does it work?

A pressurized metered-dose inhaler (MDI), the most common asthma-medication delivery system, does not indicate the quantity of medication remaining in the canister after use. Are patients with asthma using their MDIs beyond the indicated number of doses or, alternatively, disposing of them before they are empty? That is the question researchers investigated in a random sample of 500 respondents with asthma.

In a 6.5-minute telephone interview, persons who use a bronchodilator were asked 15 questions, including whether they knew how many doses the MDI contained, kept track of the number of doses used, and ever found that the MDI was empty when they needed it.

Results indicated that 31.9% of patients who used a bronchodilator did so daily and 53.8% refilled their prescriptions more frequently than is recommended by national asthma guidelines. Of bronchodilator users, 36% were told by a medical professional to keep track of MDI doses used and 87% reported having found their MDI empty during an asthma exacerbation.

These findings suggested that perhaps one third of patients are using their MDIs incorrectly through daily use of a bronchodilator; more than half refill their prescriptions too frequently; most do not have reliable means of knowing the number of remaining doses in the MDI; and the process of dosage number tracking tends to be ineffectual. The researchers concluded that dose counters should be a standard feature of MDIs.