Spectroscopic Studies on Host–Guest Interactions of α- and β-Cyclodextrin with Lidocaine Hydrochloride and Procaine Hydrochloride

Lidocaine HCl and procaine HCl are local anesthetics widely used in minor chirurgic procedures; nevertheless, spectral information about their behavior is not complete at present. In this context, in this paper, absorbance and fluorescence studies of both the drugs with α- and β-cyclodextrins (CDs) have been measured at 298.15 K. The thermodynamic parameters: binding constant (K) and standard state Gibbs energy (∆G°) were calculated for the systems in which complex formation was observed. The α- and β-CD study indicates that the lidocaine HCl and procaine HCl drugs form 1:1 inclusion complex with α- and β-CD. Both experimental and theoretical studies revealed that the phenyl ring with the amide group of the drug is encapsulated in the hydrophobic CD cavity. van der Waals interactions are mainly responsible for complex formation of lidocaine hydrochloride and procaine hydrochloride with CDs.