The role of fine particle lactose in agglomerated dry powder aerosol formulations

Performance tuning of particle engineered mannitol in dry powder inhalation formulations

Typically, smooth lactose particles are used as carrier in dry powder formulations for inhalation. Two classical approaches to improve their aerodynamic behaviour are the addition of fines (milled lactose) or magnesium stearate (MgSt). Mannitol (Parteck® M DPI) as an alternative carrier was used in this study. It has an irregular particle size distribution and a large and rough surface. This could be challenging for the detachment of micronised drug upon inhalation and it is unclear whether classic strategies for the optimisation of aerodynamic performance can be applied. In contrast, its rough surface could be an advantage in terms of drug load. To address these questions, the mannitol carrier was blended with two different drugs using various concentrations up to 50%. Self-produced mannitol fines and MgSt in different amounts and in combination were added. Blends were investigated regarding their in vitro aerodynamic performance, dosing behaviour and powder rheology. An addition of up to 30% drug load was possible while retaining good flowability and constant dosing behaviour. Despite the rough and indented carrier surface of the mannitol carrier, the addition of fines or MgSt increased the inhalable fraction, but higher concentrations of fines, as used for lactose blends, were necessary.

The role of particle properties in pharmaceutical powder inhalation formulations

Pharmaceutical aerosol delivery is undergoing dramatic changes in both inhaler device and formulation aspects. There is a rapid move from the traditional propellant-driven metered dose inhalers to the high performance liquid atomizers and dry powder inhalers (DPIs). DPIs involving the dispersion of powders into aerosols by an inhaler device are particularly attractive as dry powders generally have greater chemical stability than liquids used in atomizers. Delivery of therapeutic proteins as dry powder aerosols is of high commerical interest. However, production and formulation of dry powders for inhalation can be difficult and challenging due to the potential physical instability of the powder. Dry powders consisting of micro- or nano-sized particles are inherently adhesive and cohesive, leading to highly variable dose accuracy and poor aerosol performance. Particle engineering via the use of appropriate pharmaceutical excipients and processing parameters can produce particles of optimal morphologies and surface properties which would enhance aerosol generation. Some of the key determinants for successful dispersion of pharmaceutical powders suitable for inhalation are reviewed with an emphasis on the practical significance.