An inhaler is a handheld device that delivers medication in a measured dose while a person inhales. Inhalers are used in respiratory conditions such as asthma and chronic obstructive pulmonary disease (COPD).

Inhaled medication may work faster than oral medications to relieve symptoms such as wheezing and spasms in the bronchial tubes, because the inhaler allows the medication to go directly to the lungs. Inhaled medication usually causes fewer side effects than oral medication.

There are two types of inhalers:

• A metered-dose inhaler (MDI) is a small canister that contains medication in an aerosol form. When the person triggers the puff of medication, he or she inhales. The device measures a specific amount of medication to be released in each puff. MDIs are often used with spacers, which serve as a holding chamber for the medication. A spacer increases the amount of medication going to the lungs and can help people who have problems getting the correct timing when using an inhaler.
• A dry powder inhaler contains medication in a dry powder form. The person breathes in sharply to inhale the medication. Unlike using an MDI, no coordination between triggering the medication and inhaling is necessary. However, how well the dry powder inhaler works may depend on how well a person inhales. A dry powder inhaler should not be used with a spacer.