Development of enteric-coated fixed dose combinations of amorphous solid dispersions of ezetimibe and lovastatin: Investigation of formulation and process parameters.

Enteric-coated fixed-dose combinations of ezetimibe and lovastatin were prepared by fluid bed coating aiming to avoid the acidic conversion of lovastatin to its hydroxyacid derivative. In a two-step process, sucrose beads were layered with a glass solution of ezetimibe, lovastatin and Soluplus, top-coated with an enteric layer. The impact of different bead size, enteric polymers (Eudragit L100 and Eudragit L100-55) and coating time was investigated. Samples were evaluated by X-ray diffraction, scanning electron microscopy, laser diffraction and in vitro studies in 0.1M HCl and phosphate buffer pH 6.8. Results showed that smaller beads tend to agglomerate and release was jeopardized in acidic conditions, most likely due to irregular coating layer. Eudragit L100-55 required longer processing, but thinner coating layers provided lower drug release. Both polymers showed low drug release in acidic environment and fast release at pH 6.8. The off-line measurement of the coating thickness determined the ideal coating time as 15 and 30min for Eudragit L100-55 and Eudragit L100-based samples, respectively. Both compounds were molecularly dispersed in Soluplus, and Eudragit L100 formulations showed concave pores on the surface, presenting higher drug release in acidic conditions. Stability studies after 6 months showed unaltered physical properties and drug release.