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In this study, the potential of the spray-drying technique for preparing microspheres able to modify the release profile of carbamazepine was investigated. Low-, medium- and high-molecular-weight chitosan and hydroxypropyl methylcellulose (HPMC) in different drug-polymer ratios were used for the preparation of microspheres. The microspheres, characterized by X-ray powder diffractometry (XRD) and differential scanning calorimetry (DSC), were also studied with respect to particle size distribution, drug content and drug release. The results indicated that the entrapment efficiency (EE), as well as carbamazepine release profile, depended on polymeric composition and drug-polymer ratios of the microspheres prepared. The best entrapment efficiencies were obtained when chitosan of low-molecular-weight (CL) or HPMC were used for the microencapsulation. For all types of polymer used, the microspheres with low carbamazepine loading (6.3% w/w) showed better control of drug release than the microspheres with higher drug loadings. The HPMC microspheres showed the slowest carbamazepine release profile with no initial burst effect. Carbamazepine release profiles from ternary systems, carbamazepine-CL-HPMC microspheres, depended mostly on HPMC content and showed similar carbamazepine release profile as CL microspheres when HPMC content was low (9:1 CL-HPMC ratio, w/w). Otherwise, the carbamazepine release from CL-HPMC microspheres was remarkably faster than from either chitosan or HPMC microspheres. The release profile of carbamazepine from the microspheres was highly correlated with the crystalline changes occurring in the matrix.

The aim of this study was to develop spray-dried chitosan-based microspheres, suitable for nasal delivery of loratadine, and to evaluate their potential of modifying loratadine release. The microspheres were composed with ethylcellulose (EC) and chitosan (CM) in two different weight ratios, 1:2 and 1:3. One-phase systems (dispersions) and two-phase systems (emulsions and suspensions) were subjected to spray-drying, resulting in conventional and composed microspheres, respectively. The microspheres were evaluated with respect to the yield, particle size, encapsulation efficiency, physical state of the drug in the polymer matrix, swelling properties and in vitro drug release profile. It was shown that particle size, swelling ability and loratadine release from spray-dried microspheres were significantly affected by the polymeric composition and feed concentration in spray-drying process. Emulsifying method to produce composed EC/CM microspheres resulted in improved loratadine entrapment and moderate swelling, when compared to conventional chitosan microspheres. It seems like better formation of EC cores and chitosan coating were obtained when higher feed concentration and ultrasonic homogenization were employed in the preparation of emulsion systems and when EC to CM weight ratio was 1:3.