Chloramphenicol, cyclodextrin and amino acids ternary complexes: preparation and characterization

AIASSA V.; ZOPPI A.; ALBESA I.; LONGHI M. R.

Rosario, Santa Fe

Congreso; Segunda Reunión Internacional de Ciencias Farmacéuticas.; 2012

Introduction: Chloramphenicol (CP) is an antibacterial drug having a wide spectrum of activity against gram positive and gram negative cocci and bacilli (1). This drug presents physicochemical (low water solubility) and toxicological properties (CP stimulated oxidative stress and alters the behavior of antioxidant systems in neutrophils, among others) (2) that limit their therapeutic use. An interesting approach used to improve various properties of drugs is the formation of multicomponent complexes, constituting molecular encapsulation with B-cyclodextrin (BCD) in presence of auxiliary substances an alternative for the development of new pharmaceutical dosage forms. Based on the above-mentioned considerations, the objective of the present study was the preparation and characterization of ternary complex between CP, BCD and amino acids [L-cysteine (CYS), N-acetyl-L-cysteine (NAC) or glycine (GLI)] in aqueous solution and the solid state. The use of these amino acids for multicomponent complex formation with CP appears of special interest, for their potential ability to reduce the toxic oxidative effect of the drug due to these compounds are describes as antioxidants. Materials and Methods: The effects of complexation on drug solubility, affinity constant (KC) and the stoichiometry for the complexes were determined in water, by means of phase-solubility studies. In solid state, the ternary systems, prepared by means of simple physical mixture (PM) or by freeze-drying (FD), were studied by fourier-transform infrared spectroscopy (FT-IR), polarized light microscopy (PLM) and thermal analysis differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Results and Discussion: For all systems studied, the increase in solubility occurred as a linear function of BCD concentration, corresponding to the AL-type profile defined by Higuchi y Connors (3), where slope values less than unity indicate the occurrence of soluble complexes of 1:1 mol/mol stoichiometries. The corresponding KC, intrinsic solubility (S0), maximum solubility (Smax) and efficiency of solubility (ES, Smax/S0) values were calculated from each phase-solubility diagrams and are presented in Table 1. Taking into account the results obtained by the different techniques in solid state it is possible to confirm the formation of inclusion complexes between CP and BCD in presence of the different amino acids, when the systems were prepared by applying a FD method. On the other hand, the physical mixtures show behaviors comparable with those of the pure compounds, revealing no apparent interaction between the species in the solid state when the systems were prepared by this technique. The amorphous natures of samples obtained by FD were also confirmed by means of the previously mentioned techniques. Conclusion: The results obtained in this work show that CP is capable of producing ternary complexes in solution and solid state. This study clearly evidence that the complexation with BCD and amino acids is an effective strategy to increase the solubility of CP. Furthermore, the complexes in solid state can be prepared by FD method, which might be of use in an industrial scale. Moreover, due to the antioxidant properties of the amino acids used could reduce the oxidative effect described to CP in neutrophils, the studies to test the effect of complexation with cyclodextrins and amino acids on the toxicity of CP has already been commenced by our research group. References: 1) Brooks MH, Smith RL, Macalady DL. Inhibition of existing denitrification enzyme activity by chloramphenicol. Appl. Environ. Microbiol. 1992; 58(5):1746-53. 2) Páez PL, Becerra MC, Albesa I. Chloramphenicol-induced oxidative stress in human neutrophils. Basic Clin. Pharmacol. Toxicol. 2008. 103(4):349-53. 3) Higuchi T, Connors KA. Phase-solubility techniques, in: C.N. Reilly (Ed.), in: Adv. Anal. Chem. Instr. Wiley-Interscience, New York, 1965; 117-212.