Penicillin deterioration

FIGURE 13.5 Determination of the rate of deterioration of penicillin during storage at two different times. Note that the rate (the slope of the tangent to the curve) at 5 weeks is greater than the rate at 10 weeks, when less penicillin is present. 

Blood plasma was dehydrated from the frozen state under pressures of the order of 0.3 mm. Hg, and temperatures near —30°C. The need for dehydration arose because plasma in aqueous solution spoiled, whereas storing as a dry powder drastically reduced deterioration. Dehydration from the solid state permitted easy re-solution in water or saline solution, by virtue of the high surface-to-volume ratio characteristic of the lyophilic structure produced by this technique. The rigidity of the solid state does not permit substantial shrinkage of the drying material. Dehydration from a liquid solution, on the other hand, is accompanied by excessive volumetric shrinkage, and the result is an amorphous coagulum of low surface-to-volume ratio, and hence poor resolution. Penicillin was dehydrated in very much the same manner, then streptomycin and many other pharmaceutical products were similarly processed. 

Modes of Penicillin Degradation The main course of deterioration penicillins is hydrolysis. The course of the hydrolysis is shown in Figure 9. Dunham reviewed modes of penicillin degradation. 

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