Active Tablet Coating with Amorphous Solid Dispersion of Ibuprofen–HPMCAS from Organic Solution

Background/Objectives: As a formulation strategy to produce fixed-dose combinations with amorphous solid dispersions of poorly soluble drugs, active coating of tablets is an under-investigated topic.

Methods: In this study, ibuprofen, with a boiling point of 157 °C, was used as a model drug, and an ibuprofen–HPMCAS coating was loaded on the surface of placebo tablets using a widely used perforated laboratory pan-coater with a single two-component nozzle. Acetone, acetonitrile, and DMSO, with different boiling points and evaporation kinetics, were used as the organic solvents. HPMCAS solutions in the mentioned solvents demonstrated different viscosities due to different solvent–polymer interactions, as indicated by different solution turbidity. The concentrations of the organic solvent-containing coatings were selected based on desirable flow rates in comparison with the reference Opadry® II coating dispersion. Coatings were applied at the same pan rotation speed, but atomising and pattern air pressure, as well as drying conditions, were different.

Results: The content of residual solvents in coatings was determined with gas chromatography: low-boiling-point acetone and acetonitrile content was below the LOD, while the content of DMSO, with a boiling point of 189 °C, comprised 1.5 wt.%. A pharmacopoeial approach was utilised to assess uniformity of dosage units via uniformity of content. The accuracy of dosing decreased from acetone- and acetonitrile- to DMSO-based coatings. Because of the high boiling point of DMSO in comparison to ibuprofen, the DMSO-based coating process was the longest, and the amount of ibuprofen loss was the highest. In turn, the precision of dosing via active coating increased from acetone to acetonitrile and to DMSO. The R.S.D. of the uniformity of content decreased along with coating time and fit the power function well (R2 = 0.9843).

Conclusions: Therefore, to answer the main question of this study, proper drug dosing (in terms of accuracy and precision) using drug loading via tablet coating with this specific equipment is possible. Depending on the dose precision desired, the duration of the coating process can vary.