Improving Asthma Management: The Case for Mandatory Inclusion of Dose Counters on All Rescue Bronchodilators

Figures & data

Figure 1.— Tail-off characteristics of asthma medications delivered by MDIs with different valve placement. Panel A shows tail-off from 3 separate MDIs with fill holes located at the base of the retaining cup that allow formulation to enter the valve (valve-down orientation). Panel B shows more erratic tail-off characteristics of 3 separate MDIs with valve design in which the fill holes are located at higher levels relative to the base of the retaining cup (Adapted from Schultz (13)).

Figure 2.— Integrated dose counter on a metered-dose inhaler. Shown here is a ProAir^® metered-dose inhaler (manufactured by Teva Pharmaceutical Industries, Ltd., Horsham, PA).

Table 1.— Discrepancies in patient perceptions of the number of doses of rescue medication remaining in an MDI with no dose counter. Seventeen patients with asthma who regularly use an MDI estimated the number of salbutamol doses remaining in MDIs that had been partially emptied to different degrees (Adapted from Holt et al. (21)).

Actual number of remaining salbutamol doses in MDIs which had been partially emptied	40 doses	30 doses	20 doses	10 doses	0 doses
Range of patient estimations of the number of doses in the MDI (min–max)	0–180	0–190	0–140	0–180	0–80
Mean difference between the actual and the estimated number of doses in the MDI	76.8	81.0	63.0	54.8	23.6
Proportionate overestimations of the remaining doses in the MDI	+36.8%	+51.0%	+43.0%	+44.8%	+23.6%

Schultz RK. Drug delivery characteristics of metered-dose inhalers. J Allergy Clin Immunol 1995; 96:284–287.

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Holt S, Holt A, Weatherall M, Masoli M, Beasley R. Metered dose inhalers: A need for dose counters. Respirology 2005; 10:105–106.

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