Dry powder inhalers Flashcards
DPIs are driven by what?
Flow inspiration
What creates the energy required for fluidisation and entrainment of the formulation and deaggregation of the drug for delivery?
The patient’s forced inspiratory action
No co-ordination skill is required for pMDIs or DPIs?
DPIs
Patients need to generate what to produce the energy required to deliver the dose?
a minimum inhalation flow (Qmin)
The energy is created by the pressure drop(ΔP) that results from what?
The inhalation flow (Q) and the internal resistance of the device (R)
Internal resistance of the device affects what?
Speed and acceleration of airflow through the device
Speed of inhalation affects what?
How much drug is deposited in the lung
Can generic inhaled formulations be approved if they have in-vitro similarity?
Yes
What ways are there of approving a generic inhaled formulation?
In vitro similarity
Lung deposition equivalent and systemic PK similarity
Efficacy pharmacodynamics and systemic PK similarity
Lung deposition equivalent and safety pharmacodynamics equivalence
Delivery of respirable dose is dependent on what 3 factors?
Powder formulation
Inhalation device
Patient inspiratory flow
Particle interactions are primarily dictates by what?
Van der waals forces
Eelectrostatic forces
Capillary forces
What is the dominant force at low humidity in the absence of electrostatic forces?
Van der waals
Is van der waals a short rang or long range force?
Short
What are capillary forces?
Condensation of water vapour between contiguous bodies which forms a liquid bridge
The magnitude of capillary force directly relates to what?
Relative humidity and hydrophobicity
What is the dominant force under ambient conditions?
capillary forces
What are electrostatic forces caused by?
Frictional contact (triboelectrification) between dissimilar materials
Are electrostatic forces long or short range forces?
Long
What interactions are to be controlled and modified?
Drug-drug interactions (cohesion)
Drug-excipient interactions (adhesion)
Drug-device interactions (segregation)
What formulation strategies are there for DPIs?
Carrier-based systems
Agglomerated systems
What is an example of a carrier based excipient?
a-lactose monohydrate
What are the advantages of carrier based formulations?
Allows accurate metering of small quantities of potent drug
Improves processing of formulation
Modified lactose gives a what fold increase in therapeutic dose of salbutamol sulphate?
2.5
Fine particle lactose blending gives a what fold in therapeutic dose of salbutamol sulphate?
2
What are agglomerated powder systems used for?
High dose drugs, whereby formulation as carrier-based systems is not feasible
How are free flowing macroscopic agglomerates produced?
Via cohesive bond formation
What needs to happen to agglomerated powder systems before the drug is presented to the lungs as discrete particles?
Deaggregation
