Complexation of aspirin with potato starch and improvement of dissolution rate by dry mixing.

Functionalised particles using dry powder coating in pharmaceutical drug delivery: promises and challenges

“…In 1975, Hersey used the term 'ordered mixing' to describe the cohesive powder-blending process when fine particles are adhered on to the surface of coarse particles and termed it an 'interactive mixture' [23][24][25][26][27][28]. On the other hand, hybrid mixing or dry powder coating was introduced later and indicates a strong adhesion of the fine (guest) particles on to the surface of coarse (host) particles [17].…”

“…If the difference in size between the fine guest and the host is of at least one to two orders of magnitude, hybrid coating will ensure deposition and subsequent adhesion of the finer particles on to the surface of the coarser particles thereby overcoming disproportionate distribution of the particles in a mixture. The adhesion is due to the force that is greater than the weight of guest particles producing the ordered mixing or interactive mixture [10,24,25,29,30]. The fine guest particles are loosely (reversible process) and usually temporarily adsorbed to the host [17,24,25].…”

“…The adhesion is due to the force that is greater than the weight of guest particles producing the ordered mixing or interactive mixture [10,24,25,29,30]. The fine guest particles are loosely (reversible process) and usually temporarily adsorbed to the host [17,24,25]. Hybrid mixing or dry particle coating is used to describe a special type of ordered/interactive powder mixing.…”

“…The next set of developments were geared towards machines capable of generating high shear milling and grinding environment in order to break the agglomerates into primary fine powder followed by its deposition on to the host. An example is a device developed by the Japanese research group (Hybridiser) which was based on providing very high shear impaction force that was proven to enhance the dissolution of low solubility drug [24,25]. The device was made up of high speed motor with a processing chamber containing six blades and powder recirculation circuit.…”

“…Additionally, moisture content within host and guest particles may affect the coating process. For instance, the increase in moisture content of potato starch from 1.2 to 14.3% increased dry coating efficiency of aspirin guest particles from 2.1 to 3.5% (when 5% aspirin was added to the mixture) [25] as this could be attributed to the increase in adhesive forces owing to higher surface tension of moisture. However, Saharan [26] also reported the effect of moisture content on either stabilising or destabilising the dry coated functionalised particles, where increasing the humidity above 40% resulted in a reduction in interaction between guest (sulphonamide) and the host.…”