Penicillins: cent

Between 1941 and 1945, U.S. production of penicillin rose from virtually nothing to more than 650 billion units per month, whereas its cost dropped from 20 per 100,000 units to roughly 60 cents (Sturchio, 1988).6 The yield of penicillin was also increased about a thousand times, which was due to the following (Pelczar and Reid, 1972) ... 

A gradual drift in the ratios as shown in Figure 3 definitely indicates impurity. Figure 3 is a distribution with a sample of benzyl-penicillin which contains a few per cent of Zl -pentenylpenicillin. Experimental achievement of the curve of error indicates purity as far as the... 

Beer s law is obeyed at both maxima up to 0.04 per cent. However, they note the free acid begins to decompose in aqueous solution after only a few. hours. Chloroform solutions of penicillin V have a similar spectrum to those in water with the maxima shifted slightly to 270 and 276 nm. 

Mathews and his coworkers 8 described an unusual behavior for samples of freeze-dried potassium benzylpenicillin and potassium phenoxymethyl penicillin. These samples absorbed moisture from the air up to a maximum content of 7-14 per cent. Then the samples suddenly contracted in volume and began to lose weight until they had returned to their original weight. 

The problem of (3-lactamases became critical in 1960 when the widespread use of penicillin G led to an alarming increase of Staph, aureus infections. These problem strains had gained the lactamase enzyme and had thus gained resistance to the drug. At one point, 80 per cent of all Staph, aureus infections in hospitals were due to virulent, penicillin-resistant strains. Alarmingly, these strains were also resistant to all other available antibiotics. 

With the development in the fermentation broth of concentrations of the order of 500 O.U./cu. cm. total penicillin (80 per cent penicillin-G), the concentration procedures have not required adsorption on activated carbon (158). A presently recommended flowsheet (89) involves continuous, countercurrent, multistage extraction of the filtered and acidified (pH 2 to 2.15) broth with a one-fifth volume of amyl acetate in the centrifugal extractor at room temperature similar extraction into a volume of cold buffer solution (pH 6.8 to 7.0) acidification to pH 2 and reextraction into a K... 

Extract a quantity of the preparation (with water for benzylpenicillin) so as to give a solution containing between 160 and 190 units per ml. To a 20-ml aliquot of this solution add 50 ml of acetate buffer and then place 5-ml aliquots into each of five boiling-tubes. Place four of these tubes into a water-bath so that the level of liquid in the tubes is below that of the boiling water and allow to remain for exactly twenty-five minutes. Remove the tubes from the bath, cool and make up to 10 ml with acetate buffer in stoppered cylinders. In the meantime dilute the contents of the fifth (unheated) tube in the same way. Measure the extinction of the solutions in a 1-cm cell at 322 m/< using water in the comparison cell. Subtract the blank (unheated) solution from the mean value for the other four solutions and calculate the potency of the preparation by comparing the E(1 per cent, 1 cm) value so obtained with that obtained for a pure sample of the appropriate penicillin. 

Dissolve about 120 mg in 5 ml of water in a 15-ml centrifuge tube and cool in ice-cold w ater. Add 5 ml, accurately measured, of amyl acetate, previously saturated with the iV-ethylpiperidinium salt of benzylpenicillin cooled in ice-water and filtered. Add 0 5 ml of phosphoric acid solution (20 per cent of the B.P, acid) stopper with a wet cork, shake immediately for fifteen seconds and centrifuge for thirty seconds. Pipette off the aqueous layer completely and add to the centrifuge tube 0-5 g of freshly ignited, powdered anhydrous sodium sulphate. Stir, allow to stand in ice-water for five minutes, centrifuge for thirty seconds and replace in ice-cold water for five minutes. Pipette off a 3-ml aliquot, representing three-fifths of the weight of penicillin, into a suitable tared... 

It must be emphasised that this method is only suitable for the assay of benzylpenicillin in samples consisting substantially of benzylpenicillin. The assay should be repeated using the Standard Preparation of benzylpenicillin (dried crystalline sodium salt obtainable from the National Institute for Medical Research, assayed in terms of International Standard penicillin). The result should indicate that 95 8 per cent of the Standard is sodium benzylpenicillin if a lower value (but not less than 93 0 per cent) is obtained the assay may be considered valid and a proportionate correction should be applied to the result obtained on the sample under test. The purity of reagents is essential, particularly for the AT-ethylpiperidine. The temperature is important and should be ice cold whenever possible. If penicillin X (/)-hydroxy benzylpenicillin) is present the method may give an erroneous result, since a non-quantitative precipitation of the salt of penicillin X takes place. 

Cut the chromatograms across into strips, each containing the ten spots from one species of penicillin, which will have an average area of 75 sq. cm. Macerate each strip with 1 ml of 20 per cent ferric chloride in 01N hydrochloric acid, 10 ml of w-butanol, 2 g of anhydrous sodium sulphate and 0 6 g of sodium chloride. Hold the tubes in a water-bath at 20 until measured. The paper and salt can be packed at the bottom of the tube with a glass rod so that 7 to 8 ml of butanol can be poured off for colorimetric measurement, which is made in any suitable colorimeter. 

The determination of total penicillins is not easy. The U,S.P. uses the direct iodimetric assay as applied to benzylpenicillin after dissolving the sample in methanol, but this may lead to results which are 3 to 5 per cent low, due to interaction of procaine with iodine. Wild suggested the use of silicotungstate as a procaine precipitant before application of the iodimetric method but details given in his method required clarification. Based on the original, the following modification has been found by us to be satisfactory. 

Procaine penicillin preparations may be determined by the spectro-photometric method described by Stock (see above) but because of its low solubility in w ater, methanol is used as the extracting solvent. Procaine absorbs strongly in the ultra-violet and exhibits a maximum at 292 m/. The absorption at 322 m// (the maximum for penicillenic acid) is still significant and for pure procaine penicillin the irrelevant absorption amounts to 23 per cent of the total. I low ever, if the absorption is measured at 322 m/ both before and after the heating period, then the increase is entirely due to the penicillin present. 

Preparations such as lozenges containing sugars as diluents yield erroneous avssays by the standard method. To overcome this, add either an equivalent amount of glucose to the standard penicillin solution or 0 5 per cent of glucose to the assay plate medium. 

No effect on the colour intensity was obvious when the solutions contained high concentrations of sodium sulphate, sodium citrate, calcium chloride, 0-2 per cent sodium benzylpenicillin, 0-03 per cent procaine benzyl penicillin or 0 03 per cent penethamate hydriodide. 

In many hospitals, over 90 per cent of the nursing staff harbour penicillinase-containing, penicillin-resistant Staph, aureus in the nose, a... 

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