Q: How can one tell when a metered-dose inhaler is empty? I have been told that “floating” it is not accurate, and my drug reps haven’t been able to give me an answer.
—Rhonda Bonilla, MSN, FNP, Tulare, Calif.

A: “Floating” an inhaler in water has long been suggested as a way to determine when it is almost empty. Unfortunately, the amount of propellant in an inhaler is not equal to the amount of medication, and many patients reach for their inhaler in an emergency only to wind up receiving propellant.

Manufacturers and patient organizations now recommend counting doses. When opening a new multidose inhaler, check the label to note the number of metered sprays it contains. If you use two sprays at a time an average of three times a day, you can easily estimate when the medication will start running low. Mark this date on a daily calendar or planner. Since this is a change from previous instruction, patients need to be re-educated.
—Sherril Sego, MSN, FNP(98-9)

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