*Article* **Risperidone/Randomly Methylated** β**-Cyclodextrin Inclusion Complex—Compatibility Study with Pharmaceutical Excipients**

**Laura Sbârcea 1,2 , Ionut,-Mihai Tănase <sup>3</sup> , Adriana Ledet,i 1,2,\* , Denisa Cîrcioban 1,2 , Gabriela Vlase <sup>4</sup> , Paul Barvinschi <sup>5</sup> , Marinela Miclău 6 , Renata-Maria Văru¸t <sup>7</sup> , Oana Suciu 8,\* and Ionut, Ledet,i 1,2,3**


**Abstract:** Risperidone (RSP) is an atypical antipsychotic drug used in treating schizophrenia, behavioral, and psychological symptoms of dementia and irritability associated with autism. The drug substance is practically insoluble in water and exhibits high lipophilicity. It also presents incompatibilities with pharmaceutical excipients such as magnesium stearate, lactose, and cellulose microcrystalline. RSP encapsulation by randomly methylated β-cyclodextrin (RM-β-CD) was performed in order to enhance drug solubility and stability and improve its biopharmaceutical profile. The inclusion complex formation was evaluated using thermal methods, powder X-ray diffractometry (PXRD), universal-attenuated total reflectance Fourier transform infrared (UATR-FTIR), UV spectroscopy, and saturation solubility studies. The 1:1 stoichiometry ratio and the apparent stability constant of the inclusion complex were determined by means of the phase solubility method. The compatibility between the supramolecular adduct and pharmaceutical excipients starch, anhydrous lactose, magnesium stearate, and cellulose microcrystalline was studied employing thermoanalytical tools (TG-thermogravimetry/DTG-derivative thermogravimetry/HF-heat flow) and spectroscopic techniques (UATR-FTIR, PXRD). The compatibility study reveals that there are no interactions between the supramolecular adduct with starch, magnesium stearate, and cellulose microcrystalline, while incompatibility with anhydrous lactose is observed even under ambient conditions. The supramolecular adduct of RSP with RM-β-CD represents a valuable candidate for further research in developing new formulations with enhanced bioavailability and stability, and the results of this study allow a pertinent selection of three excipients that can be incorporated in solid dosage forms.

**Keywords:** risperidone; inclusion complex; randomly methylated β-cyclodextrin; compatibility studies; excipients; solubility; stability
