Table 1. Hypotheses concerning the working mechanism of added lactose fines.

Hypothesis	Explanation	Reference
Active sites hypothesis	Fines occupy so-called ‘active sites’ on the carrier surface, leaving only weaker binding sites available for the drug particles to bind to.	[7]
Agglomeration hypothesis	Fines form agglomerates, multiplets or multi-layers with drug particles, which are supposedly more easily detached from the carrier surface.	[7], [8]
Buffer hypothesis	Fines coarser than the drug particles may act as a buffer between colliding carrier particles and protect drug particles from press-on forces during mixing.	[11]
Fluidisation hypothesis	Fines increase the tensile strength of the bulk powder, which increases the minimum energy required for fluidisation and thus the energy available for dispersion.	[20]