Glyceryl Monooleate Cubic Phase Gel as Chemical Stability Enhancer of Cefazolin and Cefuroxime

ABSTRACT

The primary objective of this study was to determine the ability of the glyceryl monooleate (GMO) cubic phase gel to protect drugs from chemical instability reactions such as hydrolysis and oxidation. Stability was assessed on cefazolin incorporated in cubic phase gel and in solution at two different concentrations (200 and 50 μg/g), at 22, 37, and 50°C. Degradation profiles, plotting percent cefazolin remaining on a logarithmic scale versus time, were constructed and the degradation rate constants calculated from the slopes. At both concentrations, degradation of cefazolin was found to be slower in the cubic phase gel than in solution at 22 and 37°C, but not at 50°C. The degradation rate constants were 3-to 18-fold lower in the gel than in solution at low concentration of cefazolin. At 22 and 37°C, the kinetics of degradation at high concentration of cefazolin was not first-order but showed a lag phase followed by an exponential loss of cefazolin, typical of oxidation. The potential oxidation of the thioether moiety of cefazolin was confirmed by its 18-fold higher stability in the presence of ethylenediaminetetraacetic acid (EDTA) and nitrogen in solution. Cefuroxime, a cephalosporin which degrades solely via β-lactam hydrolysis, degraded twice as fast in solution as it did in the gel. The enhanced stability of cefazolin and cefuroxime in the GMO cubic phase gel shows its potential as a chemical stability enhancer and this is the first report to demonstrate oxidation, in addition to β-lactam hydrolysis, as a mechanism for degradation of cefazolin.

Key Words: :

• Cefazolin
• Cefuroxime
• Cubic phase
• Glyceryl monooleate
• Hydrolysis
• Kinetics
• Oxidation
• Stability
• Stability enhancer