Abstract

Two local anaesthetics, Bupivacaine (BVC) and Lidocaine (LDC), were studied by experimental as well as theoretical methods. These compounds were associated with a drug delivery system of cyclodextrins (CDs). We used Differential Scanning Calorimetry (DSC) for experimental measurements. We calculated enthalpy change for the process of association between drug and CD. Calculations were performed using Molecular Mechanics (MM) with MM+ and OPLS Forced Fields. Both 1:1 and 1:2 stoichiometries were studied. DSC result indicates formation of stable inclusion compounds for all cases. A difference between physical mixture and inclusion compound was observed. The OPLS GB/SA (OPLSw) results show that the difference of enthalpy change between 1:1 and 1:2 stoichiometries is ca. ±1kcalmol-1 for BVC. For LDC, the corresponding difference is ca. 10kcalmol-1. This indicates that ring out type of docking is stable for the 1:1 stoichiometry. Head-to-head alignment was predicted to be stable in 1:2 stoichiometries. 1:1 and 1:2 associations coexist and establish a dynamic equilibrium. © 2004 Elsevier B.V. All rights reserved.