Thermostability Analyses of Broad Spectrum Antibiotics Cephalexin and Ciprofloxacin via Liquid Chromatography-Mass Spectrometry

Aerial Marie Pratt


Cephalexin and ciprofloxacin are broad spectrum antibiotics that are used to treat common bacterial infections in humans. Cephalexin is considered a beta-lactam antibiotic, specifically part of the cephalosporin class of antibiotics. The antibiotic targets the bacterial cell wall and inhibits its growth. It is most effective in treating Gram-positive cocci but is somewhat active in treating Gram-negative bacilli. Cephalexin is commonly used to treat infections of the skin, ears, and urinary tract, as well as pneumonia and other respiratory tract infections. Cephalexin can also be used for patients who are allergic to penicillin.  Ciprofloxacin is part of the fluoroquinolone class of antibiotics. It targets and inhibits the bacterial enzyme DNA gyrase, preventing DNA replication. Unlike cephalexin, it is more effective in treating Gram-negative bacteria than Gram-positive bacteria. Ciprofloxacin is used to treat bacterial infections of the skin, lungs, bones, urinary tract, and also patients exposed to anthrax.

Antibiotics have recommended storage temperatures in order to maintain their reliability in treating bacterial infections. Cephalexin has a prescribed storage temperature of 35.6°F-46.4°F (2°- 8°C). Ciprofloxacin is recommended to be stored at a temperature of 35.6°F- 77°F (2°C-25°C). Higher temperatures can lead to chemical degradation of the antibiotic, rendering it ineffective.   When used routinely, antibiotics may be inadvertently stored at temperatures higher than the suggested range. Therefore it is necessary to determine the thermostability of these antibiotics when exposed to elevated temperatures.

Thermostability data will be obtained via liquid chromatography-mass spectrometry, an established analytical technique for detecting a wide array of antibiotics.  The data will be analyzed for temperatures ranging from 90°F-200°F (32°C-90°C), simulating temperature conditions in which antibiotics may be incorrectly stored. The data will be used to determine if the prescribed storage conditions for cephalexin and ciprofloxacin are valid.


Thermostability; Cehpalexin; Liquid Chromatography-Mass Spectrometry; Antibiotic

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