DPIs deliver the drug in a powdered form, which is inhaled into the lungs.
The powder formulation is crucial to ensure optimal flow, deaggregation, and deposition in the desired lung regions.
Components and Mechanism:
DPI Device Types: Single-dose, multi-dose, and capsule-based.
Dispersion Mechanism: Many DPIs utilize a patient's inhalation flow to disrupt agglomerates of drug particles, which aids in the dispersion of fine drug particles into the airstream.
Formulation Challenges:
Particle Size: For optimal deep lung deposition, particle sizes are typically optimized to be between 1 to 5 micrometers. Size distribution also affects inhaler performance.
Morphology: The shape and surface properties of particles can affect flow, dispersion, and deposition.
Agglomeration: Drug particles have a tendency to form clusters or agglomerates, which can be detrimental to inhaler performance.
Excipients:
Lactose: Often used as a carrier, which aids in flowability and aids in breaking down drug agglomerates during inhalation. The primary grades used are coarse lactose and fine lactose.
Magnesium Stearate: Sometimes used in minute quantities as a lubricant to improve powder flow.
Glidants and Surfactants: These may be used to modify the drug's physical properties, ensuring smooth flow and preventing static charge build-up.
Advantages and Disadvantages:
Patient Adherence: Because many DPIs are breath-actuated, they often require less coordination than MDIs. However, this requires patients to generate adequate inspiratory flow to ensure effective drug delivery.
