Priming a metered-dose inhaler (MDI) is a precise procedure necessary before first use to ensure the device delivers the intended dose of medication accurately. This process involves releasing test sprays into the air to establish a consistent mixture of drug and propellant within the delivery mechanism. Properly priming the MDI sets up the pressurized canister to provide the full therapeutic effect of the medicine with every puff. This mandatory step ensures safe and reliable respiratory treatment.
Why Priming Is Essential
A new or unused metered-dose inhaler contains liquid medicine and a propellant that can separate while the device sits in storage. This separation means the first few sprays may contain mostly propellant or a low concentration of the actual drug. Priming saturates the internal valve and stabilizes the medication mixture within the chamber.
This guarantees that the first therapeutic puff delivers a consistent dose containing the labeled amount of medicine. Skipping this step results in a weak or ineffective dose, which is especially problematic for rescue inhalers needed during sudden breathing difficulties.
Determining When Repriming Is Necessary
Priming is always required before using a brand-new metered-dose inhaler. Beyond initial use, repriming is necessary to maintain dose accuracy in specific scenarios. This includes if the inhaler has been accidentally dropped, which can disrupt the internal mechanism and the medication mixture.
Repriming is also mandatory if the inhaler has not been used for a specific period of time. This duration varies by manufacturer and product, often ranging from five days to one month. Always check the product’s patient information leaflet for the exact time frame that requires repriming.
Step-by-Step Guide to Priming Your Inhaler
Preparation
Before beginning the priming process, check the expiration date printed on the canister and ensure the dose counter, if present, is working correctly. Remove the protective cap from the mouthpiece and inspect the opening to confirm it is clean and free of any debris or powder.
Shake and Position
The next step is to shake the inhaler vigorously for several seconds, typically about five seconds, to thoroughly mix the medicine and the propellant inside the pressurized canister. Holding the inhaler upright, point the mouthpiece away from your face and other people, making sure you are in an open area.
Actuation
Actuate the inhaler by firmly pressing down on the canister once to release a spray into the air. This test spray confirms the device is functioning and begins the process of loading the valve with a consistent mixture. Repeat the process of shaking the inhaler and releasing a spray into the air for the total number of test sprays specified in the instructions.
Completion
The exact number of sprays needed for priming is product-specific, commonly ranging from two to four sprays depending on the medication. If the instructions require multiple test sprays, a brief pause is sometimes needed between each actuation and shake, so always consult the specific product instructions. Once the full number of required test sprays has been released, the inhaler is now ready to deliver an accurate dose of medicine.