Metered-dose inhaler
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Albuterol Sulfate(US)
A metered-dose inhaler (MDI) is a device that helps deliver a specific amount of medication to the lungs. It is commonly used to treat asthma, chronic obstructive pulmonary disease (COPD), and other respiratory problems. Because of normal naming conventions, MDIs are considered aerosolized.
An inhaler consists of 2 major components. The canister and a mouthpiece. The canister itself consists a metering dose valve with an actuating stem, with the inside containing the aerosol propellant and medication. The mouthpiece contains the mating discharge nozzle and generally includes a dust cap to prevent contamination.
Once assembled the patient then uses the inhaler by pressing down on the top of the canister, with their thumb supporting lower portion of the mouthpiece, thus releases a mist of medicine that is then breathed into the lungs.
The medication in a metered dose inhaler is most commonly a bronchodilator, corticosteroid or a combination of those two. Other medications less commonly used but also administered by MDI are mast cell stabilizers, such as (cromoglicate or nedocromil).
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[edit] Uses
Asthma inhalers are devices for treating asthma. They contain an asthma medication--a drug that treats the symptoms of asthma. In one variety of beclomethasone inhaler, the combination of increased absorption and better particle size has resulted in an increase of potency of 180%, however for the salbutamol inhalers the effectiveness and dose required remain unchanged. Other systems involve micronised powder packaged for example in single dose quantities in blisters or gel capsules containing the powdered medication drawn into the lungs by the user's own breath. These systems tend to be more expensive than the MDI, and at the time the user most needs them it may be difficult to generate enough airflow to get good function from them. However, they do not affect the ozone layer.
A nicotine inhaler allows cigarette smokers to get nicotine without having to use tobacco, much like nicotine gum or a nicotine patch. Nicotine inhalers can be used indoors and in places that are affected by smoking bans. They produce no second-hand smoke, only an odorless vapor. Nicotine inhalers do not contain tobacco, yet they replicate the process of smoking including the immediate "buzz" that comes from cigarettes. They can be used as an alternative to smoking. They can also be used by smokers who do not want have it more and more.
Double blind clinical trials of such inhalers have shown to have sustained a reduction in smoking for four months in 52 of 400 participants (26%) in the test group. In the placebo group only 18 of 400 (9%) reduced their smoking habits.
[edit] Spacers
Spacers are tubes attached to the inhaler that act as a reservoir or holding chamber. They serve to hold the medication that is sprayed by the inhaler. This makes it easier to use the inhaler and helps ensure that more of the medication gets into the lungs instead of just into the mouth or the air. With proper use, a spacer can make an inhaler 12 percent more effective in delivering medicine.[1]
Spacers can be especially helpful to adults and children who find a regular inhaler hard to use. People who use corticosteroid inhalers should use a spacer to prevent getting the medicine in their mouth, where oral yeast infections can occur.
[edit] When does an inhaler need to be replaced?
A metered dose inhaler contains enough medication for a certain number of puffs which is printed on the canister. Even though the inhaler may continue to work beyond that number of uses, the amount of medication delivered may not be correct. It is important to keep track of the number of times an inhaler was used, so that it can be replaced after its recommended number of uses. The manufacturer of Ventolin and Advair have addressed this issue by adding in a counter to the mouthpiece. Also, depending on the manufacturer, inhalers are sold as a complete unit or the individual canister as a refill prescription.
[edit] Discontinuation of CFC Inhalers
In the United States starting from December 2008 inhalers containing chlorofluorocarbons, as a form of propellant to deliver the medication, will be discontinued for hydro-fluoroalkane-pressurized metered dose inhalers (HFA pMDI's).[citation needed] As governed by the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer, all inhalers that contain CFCs are being discontinued with the target year 2010 under the auspices of the UN Environment Programme[2].
[edit] See also
[edit] References
- ^ Togger, D., & Brenner, P. (2001). Metered dose inhalers. American Journal of Nursing, 101 (10), 29.
- ^ The Montreal Protocol on Substances that Deplete the Ozone Layer. United Nations Environment Programme.
[edit] External links
- UpToDate Patient Information: Metered dose inhaler techniques in adults
- Ourasthma.com – a patient-oriented site with information on asthma inhalers.
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