Inclusions of lidocaine hydrochloride in cyclodextrins were prepared to obtain stable complexes compatible for association with chlorhexidine in a new gel formulation for use in urogenital applications. Two cyclodextrins, β-cyclodextrin and methyl-β-cyclodextrin, were used for encapsulating lidocaine hydrochloride through solubilization and kneading techniques. The lidocaine-cyclodextrin complexes were characterized by ultraviolet spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, and X-ray diffraction. The results revealed that the techniques generated good yields of inclusion products that maintained the functional properties of lidocaine. In addition, the inclusion products obtained improved the compatibility of lidocaine hydrochloride with chlorhexidine in solution and a gel formulation. The gel formulation displayed desirable rheological and physicochemical properties. The results presented here are the first description of the inclusion of lidocaine with cyclodextrins, which improves compatibility with chlorhexidine in formulations for simultaneous delivery.
Keywords: chlorhexidine gluconate incompatibility; cyclodextrins; lidocaine hydrochloride; solubilization and kneading inclusion techniques; urogenital gel formulations.