A metered-dose inhaler (MDI) consists of a canister of pressurized medication that fits into a plastic actuator sleeve and connects to a mouthpiece. An MDI propels medication at over 60 miles per hour, and that medication needs to make a sharp turn to effectively get into the airways of your lungs.

Therefore, most of the medication sprayed from the MDI never even reaches your lungs. For example, the spray can coat your mouth, the end of your tongue, or the back of your throat. In the best-case scenario, your small airways receive only 10 to 20 percent of the inhaled medication.

Inhalers help millions of people with asthma breathe easier, but properly using inhalers is crucial to their success. Many people around the world experience difficulty controlling their asthma because they use their inhalers incorrectly.

1. Remove the cap and hold the inhaler upright.
2. Shake the inhaler.
3. Tilt your head back slightly and breathe out slowly.
4. Depending on your physician’s specific instructions, open your mouth with your head one to two inches away from the inhaler or position the inhaler in your mouth.
5. Press down on the inhaler to release medication as you start inhaling or within the first second of inhaling; continue inhaling as you press down on your inhaler. Breathe in slowly through your mouth, not your nose, for three to five seconds. Press your inhaler only once while you’re inhaling (one breath for each puff). Make sure you breathe evenly and deeply.
6. Hold your breath for 10 seconds to allow the medicine to reach deep into your lungs.
7. Repeat puffs as your prescription dictates. Waiting one minute between puffs may permit the second puff to reach into the airways of your lungs better.

As an MDI reaches its empty stage, dose reliability becomes increasingly unpredictable. Therefore, you should not use your inhaler beyond the labeled number of doses (check the label on the side of the canister), even if you think that some medication remains.

Reprinted from Allergies and Asthma for Dummies by William Berger, M.D. Available wherever you buy books.