According to recent research from Changchun, People's Republic of China, "A 4-week sustained release risperidone biodegradable poly(D, L-lactide-co-glycolide) (PLGA) microsphere for the therapy, of schizophrenia, the effects of formulation parameters on encapsulation efficiency and release behavior were studied. The risperidone PLGA microspheres were prepared by O/W solvent evaporation method and characterized by HPLC, SEM, laser particle size analysis, GC and HPLC-MS."

"The results indicated that the morphology of the risperidone PLGA microspheres presented a spherical shape with smooth surface, the particle size was distributed front 32 to 92, mu m and the drug encapsulation efficiency was influenced by homogeneous rotation speed, intrinsic viscosity, carboxylic terminal group, the polymer concentration in the oil phase and the molecular weight of the polymer. These changes were also reflected in drug release. When the Mw of the polymers increased front ca. 28000 to ca. 90000, the initial burst release of risperidone PLGA microspheres decreased front 13 to 0.8% and the sustained-release could be extended to 4 weeks. Pharmacokinetic study on beagle dogs showed that the 4-week sustained release profile of the risperidone loaded microspheres prepared with 75253A was verified," wrote Z.X. Su and colleagues, Jilin University (see also Risperidone Therapy).

The researchers concluded: "The PLGA 75253A and 75255A show the potential as excipients for the monthly sustained release risperidone PLGA microspheres due to higher encapsulation efficiency and almost zero-order release kinetics of release profile."

Su and colleagues published their study in Chemical & Pharmaceutical Bulletin (Effects of Formulation Parameters on Encapsulation Efficiency and Release Behavior of Risperidone Poly(D, L-lactide-co-glycolide) Microsphere. Chemical & Pharmaceutical Bulletin, 2009;57(11):1251-1256).

For additional information, contact Y.X. Li, Jilin University, College Life Science, 2699 Qianjin St., Changchun 130023, People's Republic of China.

Publisher contact information for the journal Chemical & Pharmaceutical Bulletin is: Pharmaceutical Society Japan, 2-12-15-201 Shibuya, Shibuya-Ku, Tokyo, 150, Japan.