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Background: Milling and mixing are unit operations that are often employed in drug formulation.

Objective: This study aims at investigating the physicochemical and release properties of drug formulations containing ibuprofen and different polymers prepared with different milling techniques and freeze-drying.

Methods: Acha rice starch (ACS) and Ofada rice starch (OFS) were extracted from grains of Digitaria exilis and Oryza glaberrima, respectively. Binary mixtures of ibuprofen and ACS, OFS or Hydroxypropyl methyl cellulose (HPMC) were prepared by physical mixing, ball milling and beads milling. Particles from beads milling were freeze-dried. The formulations were evaluated, using particle size analysis, FT-IR, PXRD, scanning electron microscopy and in-vitro release studies.

Results: All the techniques resulted in particle size reduction in the rank order of Freeze-drying > Beads milling > Ball milling > Physical mixing (p < 0.05). Formulations containing OFS and HPMC attained highest particle size reduction with beads milling, while ball mill resulted in highest size reduction in formulations containing ACS.
Increasing starch concentration reduced the crystallinity of ibuprofen. Particles of ACS and OFS were more spherical and aggregating than those of HPMC. Formulations containing OFS exhibited highest drug release (p>0.05) with rank order OFS > ACS > HPMC. Drug release from the starches was higher than from HPMC.

Conclusion: The starches possess better physicochemical properties compared to HPMC. Freeze-drying produces formulations with smallest particle sizes and highest reduction of crystallinity of the API. Ofada rice starch formulations are characterized by the best drug release.
Key words: Milling, Ibuprofen, Starch, Formulations, Particle size