Utilization of a kinetic isotope effect to decrease decomposition of ceftriaxone in a mixture of D₂O/H₂O.

Area of Science:

• Pharmaceutical Chemistry
• Chemical Kinetics
• Antibiotic Stability

Background:

• Cephalosporins are crucial β-lactam antibiotics, offering improved stability and activity over penicillins.
• Despite enhanced stability, cephalosporins undergo various chemical transformations, impacting their efficacy.
• Understanding ceftriaxone degradation is vital for optimizing its therapeutic applications.

Purpose of the Study:

• To investigate the degradation rates and mechanisms of ceftriaxone in aqueous solutions.
• To elucidate the influence of deuterium oxide on ceftriaxone's chemical stability.
• To identify ceftriaxone degradation products and understand the underlying chemical processes.

Main Methods:

• Comparative analysis of ceftriaxone degradation in H2O, D2O, and mixtures at neutral pH.
• Utilizing High-Performance Liquid Chromatography (HPLC) for initial rates determination.
• Employing quantitative 1H Nuclear Magnetic Resonance (NMR) spectroscopy.
• Applying computational analysis for molecular-level insights.

Main Results:

• Identified specific ceftriaxone degradation products, including a novel dimer-type species.
• Observed a significant kinetic isotope effect (KIE) when comparing degradation in H2O and D2O.
• Demonstrated that deuterium oxide significantly retards ceftriaxone degradation compared to water.
• Computational modeling provided molecular explanations for the observed degradation pathways and stabilization by D2O.

Conclusions:

• The study provides valuable insights into the initial degradation pathways of ceftriaxone.
• The kinetic isotope effect confirms the involvement of proton transfer in the rate-limiting step of degradation.
• Deuterium oxide offers a stabilizing effect on ceftriaxone, potentially extending its shelf-life and therapeutic utility.