Dry Powder Inhaler
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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 disease Respiratory diseases, or lung diseases, are pathology, pathological conditions affecting the organs and tissues that make gas exchange difficult in Breathing, air-breathing animals. They include conditions of the respiratory tract including the t ...
s such as
asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...
,
bronchitis Bronchitis is inflammation of the bronchi (large and medium-sized airways) in the lungs that causes coughing. Bronchitis usually begins as an infection in the nose, ears, throat, or sinuses. The infection then makes its way down to the bronchi. ...
,
emphysema Emphysema, or pulmonary emphysema, is a lower respiratory tract disease, characterised by air-filled spaces ( pneumatoses) in the lungs, that can vary in size and may be very large. The spaces are caused by the breakdown of the walls of the alve ...
and
COPD Chronic obstructive pulmonary disease (COPD) is a type of progressive lung disease characterized by long-term respiratory symptoms and airflow limitation. The main symptoms include shortness of breath and a cough, which may or may not produce mu ...
although DPIs (such as
Inhalable insulin Inhalable insulin is a powdered form of insulin, delivered with an inhaler into the lungs where it is absorbed. In general inhaled insulins have been more rapidly absorbed than Subcutaneous injection, subcutaneous injected insulin, with faster peak ...
) have also been used in the treatment of
diabetes mellitus Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...
. DPIs are an alternative to the aerosol-based inhalers commonly called
metered-dose inhaler A metered-dose inhaler (MDI) is a device that delivers a specific amount of medication to the lungs, in the form of a short burst of aerosolized medicine that is usually self-administered by the patient via inhalation. It is the most commonly used ...
(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 in a proprietary form inside the inhaler. Once loaded or actuated, the operator puts the mouthpiece of the inhaler into their mouth and takes a sharp, deep inhalation (ensuring that the medication reaches the lower parts of the lungs), 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 A cough is a sudden expulsion of air through the large breathing passages that can help clear them of fluids, irritants, foreign particles and microbes. As a protective reflex, coughing can be repetitive with the cough reflex following three pha ...
. Most DPIs rely on the force of patient inhalation to entrain powder from the device and subsequently break-up the powder into particles that are small enough to reach the lungs. 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.


Inhaler Technique and Use

While DPIs are commonly used in the treatment of lung-based disorders, their use requires dexterity to complete the required sequential steps to achieve application of these devices. Incorrect completion of one or more steps in the use of a DPI can substantially reduce the delivery of the administrated medication and consequently its effectiveness and safety. Numerous studies have demonstrated that between 50 and 100% of patients do not use their inhaler devices correctly, with patients often unaware that they are using their inhaled medication incorrectly. Incorrect inhaler technique has been associated with poorer outcomes.


Lactose

Some powder inhalers use
lactose Lactose is a disaccharide sugar synthesized by galactose and glucose subunits and has the molecular formula C12H22O11. Lactose makes up around 2–8% of milk (by mass). The name comes from ' (gen. '), the Latin word for milk, plus the suffix '' - ...
to: # Carry the fine particles of the active pharmaceutical ingredient (which must be fine to reach its target) # Improve the flow-ability of the powder during manufacturing and to aid handling # Act as a bulking agent # Aid in powder uptake from the device during inhalation and aerosolization It has been suggested that such
lactose Lactose is a disaccharide sugar synthesized by galactose and glucose subunits and has the molecular formula C12H22O11. Lactose makes up around 2–8% of milk (by mass). The name comes from ' (gen. '), the Latin word for milk, plus the suffix '' - ...
may be harmful to
lactose intolerant Lactose intolerance is a common condition caused by a decreased ability to digest lactose, a sugar found in dairy products. Those affected vary in the amount of lactose they can tolerate before symptoms develop. Symptoms may include abdominal ...
people, and some doctors advise patients not to use lactose containing DPIs to minimize the risk of hypersensitivity reactions.


Storage

DPI medication must be stored in a dry place in a temperature of not more than 25 °C (77 °F) and humidity between 40 and 50% in a sealed packaging, since exposure of the powder to moisture degrades the ability of the device to disperse its medication as a fine powder upon inhalation. Some medication also needs photo protection.


See also

*
Inhaler An inhaler (also known as a puffer, pump or allergy spray) is a medical device used for delivering medicines into the lungs through the work of a person's breathing. This allows medicines to be delivered to and absorbed in the lungs, which prov ...
*
Metered-dose inhaler A metered-dose inhaler (MDI) is a device that delivers a specific amount of medication to the lungs, in the form of a short burst of aerosolized medicine that is usually self-administered by the patient via inhalation. It is the most commonly used ...
*
Nebulizer In medicine, a nebulizer (American English) or nebuliser (British English) is a drug delivery device used to administer medication in the form of a mist inhaled into the lungs. Nebulizers are commonly used for the treatment of asthma, cystic fibro ...


References


Further reading


Guidance for Industry: Metered Dose Inhaler (MDI) and Dry Powder Inhaler (DPI) Drug Products
– Food and Drug Administration Center for Drug Evaluation and Research (CDER)
The Diskus(tm) Inhaler
– Medscape Today clinical drug investigation {{Dosage forms, state=expanded Dosage forms Drug delivery devices Medical treatments Powders