Formation and Structure of Polymers

Smith et al. (1971) have determined the amount of polymers (i.e., substances which elute in the higher molecular weight range on Sephadex G-25 gel chromatography) formed in aqueous solutions (25% W/V) of a number of penicillins stored at room temperature. The solutions were not buffered. The results obtained are shown in Table 1. In another study, these investigators (Dewdney et al. 1971) have demonstrated that the amounts of polymers formed in a 25% W/V solution of benzylpenicillin sodium are greatly reduced if a phosphate buffer (pH 7.5) is included in the solution. A similar observation has also been made by de Weck et al. (1968) in the case of a 10% W/V penicillin solution. This reduction in polymerization 

Minimum amount of polymer required to elicit a passive cutaneous anaphylaxis reaction 

More detailed investigations of the rate and factors affecting the rate of dimerization and polymerization of benzylpenicillin and similar penicillins remain to be carried out. 

Smith and Marshall (1971) have also investigated the structure of polymers formed in aqueous solutions of 6-APA and ampicillin. From 14-day-old 25% W/V solutions of the sodium salts of these compounds 1.6% (ampicillin) and 3.4% (6-APA) of polymeric substances were isolated. The analytic data for the ampicillin polymer ( =4.1) were reported to be consistent with the structure suggested by 

On the basis of the established structure of ampicillin polymers and from kinetic investigations of the decomposition of ampicillin in aqueous solution, including an examination of the influence of pH and ampicillin concentration on the 

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