Influence of coating material on the flowability and dissolution of dry-coated fine ibuprofen powders

This study investigates the effects of a variety of coating materials on the flowability and dissolution of dry-coated cohesive ibuprofen powders, with the ultimate aim to use these in oral dosage forms. A mechanofusion approach was employed to apply a 1% (w/w) dry coating onto ibuprofen powder with coating materials including magnesium stearate (MgSt), L-leucine, sodium stearyl fumarate (SSF) and silica-R972. No significant difference in particle size or shape was measured following mechanofusion with any material. Powder flow behaviours characterised by the Freeman FT4 system indicated coatings of MgSt, L-leucine and silica-R972 produced a notable surface modification and substantially improved flow compared to the unprocessed and SSF-mechanofused powders. ToF-SIMS provided a qualitative measure of coating extent, and indicated a near-complete layer on the drug particle surface after dry coating with MgSt or silica-R972. Of particular note, the dissolution rates of all mechanofused powders were enhanced even with a coating of a highly hydrophobic material such as magnesium stearate. This surprising increase in dissolution rate of the mechanofused powders was attributed to the lower cohesion and the reduced agglomeration after mechanical coating.