Thermal decomposition of amorphous beta-lactam antibacterials

Area of Science:

• Pharmaceutical Science
• Solid-State Chemistry
• Physical Chemistry

Background:

• Amorphous forms of drugs can exhibit different stability profiles compared to their crystalline counterparts.
• Understanding the thermal decomposition pathways of antibiotics is crucial for formulation and storage.
• Penicillin G potassium, cephalothin sodium, cefamandole sodium, and cefamandole nafate are important beta-lactam antibiotics.

Purpose of the Study:

• To investigate the thermal decomposition rates of amorphous beta-lactam antibiotics.
• To determine the influence of water content and temperature on the stability of amorphous cephalosporins.
• To compare the stability of amorphous and crystalline forms of these antibiotics.

Main Methods:

• Thermogravimetric analysis (TGA) was used to determine decomposition rates.
• Experiments were conducted across a range of temperatures and water content levels.
• Kinetic analysis, including Arrhenius plots, was applied to the decomposition data.

Main Results:

• Amorphous cephalosporins were significantly less stable than their unsolvated crystalline forms, even when rigorously dry.
• Absorbed water increased both the number of decomposition products and the overall decomposition rate.
• Nonlinear Arrhenius plots were observed, suggesting complex decomposition mechanisms possibly involving molecular relaxation.

Conclusions:

• The solid-state form (amorphous vs. crystalline) critically impacts the thermal stability of these antibiotics.
• Water content plays a significant role in accelerating the decomposition of amorphous cephalosporins.
• The findings suggest that crystalline forms offer superior stability for these pharmaceutical compounds.