A Dry powder inhaler (DPI) is a device that delivers medication to the lungs in the form of a dry powder. DPIs are commonly used to treat respiratory diseases such as asthma, bronchitis, emphysema and COPD although DPIs have also been used in the treatment of diabetes mellitus.^[1]

DPIs are an alternative to the aerosol based inhalers commonly called metered-dose inhaler (or MDI). The DPIs may require some procedure to allow a measured dose of powder to be ready for the patient to take. The medication is commonly held either in a capsule for manual loading or a proprietary form from inside the inhaler. Once loaded or actuated, the operator puts the mouthpiece of the inhaler into their mouth and takes a deep inhalation, holding their breath for 5-10 seconds. There are a variety of such devices. The dose that can be delivered is typically less than a few tens of milligrams in a single breath since larger powder doses may lead to provocation of cough.

Most DPIs rely on the force of patient inhalation to entrain powder from the device and subsequently break-up the powder into aerosol particles that are small enough to reach the lungs.^[2] For this reason, insufficient patient inhalation flow rates may lead to reduced dose delivery and incomplete deaggregation of the powder, leading to unsatisfactory device performance. Thus, most DPIs have a minimum inspiratory effort that is needed for proper use and it is for this reason that such DPIs are normally used only in older children and adults.

[edit] Lactose

Some powder inhalers use lactose as bulking agent and to aid in powder uptake from the device during inhalation. While some have suggested that such lactose may be harmful to lactose intolerant people,^[3] the lactose dose delivered by dry powder inhalers is typically less than a few milligrams and such doses do not lead to clinically relevant concerns of adverse effects in lactose intolerant patients.

[edit] Storage

DPI medication must be stored in a dry place or sealed packaging, since exposure of the powder to moisture degrades the ability of the device to disperse its medication as an aerosol upon inhalation.

[edit] See also

• Inhaler
• Metered-dose inhaler
• Nebulizer

[edit] References

1. ^ "Exubera Prescribing Information (PDF)". Pfizer. April 2008. http://www.fda.gov/cder/foi/label/2006/021868mg.pdf. Retrieved 2009-02-27. 
2. ^ Finlay, Warren H. (2001). The mechanics of inhaled pharmaceutical aerosols: an introduction. Boston: Academic Press. ISBN 0-12-256971-7. 
3. ^ Changes in Inhaler Devices for Asthma And COPD - Health - RedOrbit

[edit] Further reading

• Metered Dose Inhaler (MDI) and Dry Powder Inhaler (DPI) Drug Products Chemistry, Manufacturing, and Controls Documentation Food and Drug Administration Center for Drug Evaluation and Research (CDER)
• The Diskus(tm) Inhaler Medscape Today - Clinical Drug Investigation

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