Investigation of the potential for direct compaction of a fine ibuprofen powder dry-coated with magnesium stearate

Abstract

Intensive dry powder coating (mechanofusion) with tablet lubricants has previously been shown to give substantial powder flow improvement. This study explores whether the mechanofusion of magnesium stearate (MgSt), on a fine drug powder can substantially improve flow, without preventing the powder from being directly compacted into tablets. A fine ibuprofen powder, which is both cohesive and possesses a low-melting point, was dry coated via mechanofusion with between 0.1% and 5% (w/w) MgSt. Traditional low-shear blending was also employed as a comparison. No significant difference in particle size or shape was measured following mechanofusion. For the low-shear blended powders, only marginal improvement in flowability was obtained. However, after mechanofusion, substantial improvements in the flow properties were demonstrated. Both XPS and ToF-SIMS demonstrated high degrees of a nano-scale coating coverage of MgSt on the particle surfaces from optimized mechanofusion. The study showed that robust tablets were produced from the selected mechanofused powders, at high-dose concentration and tablet tensile strength was further optimized via addition of a Polyvinylpyrrolidone (PVP) binder (10% w/w). The tablets with the mechanofused powder (with or without PVP) also exhibited significantly lower ejection stress than those made of the raw powder, demonstrating good lubrication. Surprisingly, the release rate of drug from the tablets made with the mechanofused powder was not retarded. This is the first study to demonstrate such a single-step dry coating of model drug with MgSt, with promising flow improvement, flow-aid and lubrication effects, tabletability and also non-inhibited dissolution rate.

• Fine powder
• ibuprofen
• mechanical dry powder coating
• mechanofusion
• powder flow
• tableting
• tensile strength

Acknowledgements

Thanks to BASF for kind donation of the ibuprofen. Li Qu would like to acknowledge the scholarship support from Monash Graduate Scholarship and Monash International Research Scholarship. The authors also acknowledge the facilities, and scientific and technical assistance of the Australian Microscopy & Microanalysis Research Facility at the South Australian Regional Facility (SARF), University of South Australia, a facility that is funded by the University, and State and Federal Governments.

Declaration of interest

The authors report no declaration of interest.