Azidocillin

UV and VIS spectrophotometric methods, after previous chromatographic separation (TLC/UV) and iodometric methods were adapted for the determination of azidocillin in presence of its breakdown products. These methods were applied for kinetic measurement of changes in the azidocillin concentration with time in water solutions and solid state. Using thin layer chromatography several decomposition products of azidocillin were detected.

The decomposition rate at elevated temperature was studied of the following penicillins: ampicillin trihydrate (1), 6-aminopenicillanic acid (2; 6-APA), amoxicillin trihydrate (3), piperacillin (4), amoxicillin sodium (5), azlocillin sodium (6), mezlocillin sodium monohydrate (7) and azidocillin sodium (8). The pattern of decomposition was found to comply with the first-order reaction. The thermal stability of the compounds at 25 degrees C increased in accordance with the sequence 1 less than 2 less than 3 much less than 6 less than 5 less than 8 less then 7 much less than 4, which was connected with the hydrophilic and lipophilic properties of these penicillins. An isokinetic enthalpy-entrophy correlation was demonstrated. The calculated beta value was 420 K.

Intestinal absorption rate constants of amoxicillin, ampicillin, epicillin, cyclacillin and azidocillin, by means of a static in situ intestinal perfusion method has been estimated. Luminal remaining antibiotic concentrations were determined using a standard microbiological technique. In order to establish statistically better absorption kinetics, five dose levels were used, ranging from 10 to 1000 micrograms/ml, and first order, Michaelis-Menten and combined first-order and Michaelis-Menten differential model equations were fitted to experimental data found for each antibiotic. According to the AIC test, the best equation for absorption kinetics was selected. Amoxicillin and ampicillin absorption mechanisms were better described by combined kinetics, while for cyclacillin and epicillin the most probable kinetics was that of Michaelis-Menten. For azidocillin, the only non-aminopenicillin component of this series, first order kinetics should be statistically selected.