Lactose composite carriers for respiratory delivery

Purpose: Lactose dry powder inhaler (DPI) carriers, constructed of smaller sub units (composite carriers), were evaluated to assess their potential for minimising drug–carrier adhesion, variability in drug–carrier forces and influence on drug aerosol performance from carrier–drug blends.

Methods: Lactose carrier particles were prepared by fusing sub units of lactose (either 2, 6 or 10 μm) in saturated lactose slurry. The resultant composite particles, as well as supplied lactose, were sieve fractioned to obtain a 63–90 μm carriers. The carriers were evaluated in terms of size (laser diffraction) morphology (electron microscopy and atomic force microscopy), crystallinity and drug adhesion (colloid probe microscopy). In addition, blends containing drug and carrier were prepared and evaluated in terms of drug aerosol performance.

Results: The surface morphology and physico-chemical properties of the composite carriers were significantly different. Depending on the initial primary lactose size, the composite particles could be prepared with different surface roughness. Variation in composite roughness could be related to the change in drug adhesion (via modification in contact geometry) and thus drug aerosol performance from drug–lactose blends.

Conclusion: Composite based carriers are a potential route to control drug–carrier adhesion forces and variability thus allowing more precise control of formulation performance.