Whichever technique you use, please consider the following: If you notice "smoke" coming out of your mouth, or if you feel most of the medication remains in your mouth and not your chest, you are not using your inhaler properly. You should demonstrate your technique to your asthma specialists.
When you use your inhaler, be sure to clean it at the end of the day or at least every few days. Remove the dust cap and the canister (medication container). Wash the mouthpiece with warm soapy water and rinse it well. Allow 30 minutes for drying before use. Replace the canister and cap in the housing. If your inhaler gets dirty when you keep it in your pocket or pocketbook, you should first place it in a plastic bag to keep it clean and prevent yourself from accidentally inhaling dirt or a foreign object.
In order to judge if an inhaler is empty, some people drop the metal portion of the inhaler in a sink of water, thinking that its position (floating = empty, sinking = full) in the water will tell how much medication is left. This is not accurate. Shaking the inhaler or checking if it still "puffs" are also inaccurate methods for determining the amount of medication left. The Asthma Center specialists feel that a much more accurate method is to divide the actual number of doses that a new MDI contains by the number of puffs used each day (daily dose) to calculate the number of days of treatment your inhaler holds.
For example, if your MDI contains 200 puffs and you know that you inhale 2 puffs twice a day (4 puffs a day), you can then divide 200 puffs (total number of doses) by 4 (total daily dose) to determine the total remaining days of use. In this case the MDI contains 50 days of medication use before it will empty (200 divided by 4). Based on this information, simply write the predetermined date of replacement onto the canister with a permanent marking pen and also on your personal calendar.
Using this information, you can confidently determine when the canister will be empty and replace it in a timely fashion. It should be noted that it is possible that occasionally there will be less total doses in your MDI than indicated; therefore, replace the canister well in advance of total expiration. The Asthma Center specialists have found that this is the best replacement strategy.
If you use MDIs only occasionally for symptoms, it is probably best to replace your inhalers at least every 6 months, even though they still may contain lots of medication. Of course, if the inhaler has not been used at all, you can replace it according to the manufacturer's expiration date marked on the box of the MDI and on the canister.