DPIs

Question 1

DPIs

Answer 1

• delivers drugs directly into the lungs using a dry powder formulation
• no propellant is used

A DPI device must :
- protect the powder formulation from the environment until needed
- accurately dispense a precise dose
- use airflow to liberate the drug
- offer the potential for multi-dose usage

Question 2

Single dose DPI designs

Answer 2

• capsule inserted into the centre chamber
• device pierces the capsule
• patient inhales the contents through the mouthpiece

Question 3

Multi Dose DPI Designs

Answer 3

BULK RESERVOIR
- can store many doses and is dispensed via a mechanical action for inhalation
- correct dose is measured out by rotating disc arrangement with device

Question 4

Formulation of DPIs

Answer 4

• particle size in DPI formulations plays a crucial role in determining the deposition site within the lungs
• achieving proper drug deposition requires a good airflow in the device. Insufficient airflow can cause particle aggregation to occur. Non cohesive particles are ideal because they flow easily and disaggregate easily during inhalation
• small particles tend to stick together due to cohesive forces leading to aggregation. This can cause issues during inhalation because larger lumps may deposit in the wrong part of the RT
• Since the air in the lungs is highly humid, moisture can condense on the hygroscopic particles causes them to swell and increase in size. This can result in less effective deposition. To overcome this particles are coated with hydrophobic substances that repel moisture.

Question 5

Factors promoting disaggregation

Answer 5

• carrier particle size
• surface roughness
• moisture content

Question 6

Advantages and Disadvantages of PDIs

Answer 6

ADVANTAGES
- activated by pts inhalation
- more effective lung deposition than PMDIs
- formulates as solid particle blends offering stability and reduced degradation

DISADVANTAGES
– rely on patients inhalation limiting controlled delivery
- currently used for topical drug delivery but may not be ideal for systemic therapies with narrow therapeutic windows
- development of power assisted devices is ongoing, but availability remains limited

Question 7

Environmental Impact

Answer 7

pMDIs
- can contribute to greenhouse gas emission due to HFA
- disposal can cause issues
- propellants need to be disposed of in a controlled way to prevent them from being released into the atmosphere

DPIs
- do not use propellants making them environmentally friendly