Studies on the formation and activity of the transformation product of ampicillin

Bioavailability of hetacillin in rats after liver enzyme induction by various inducers with or without protein binding properties

The serum levels and the half life of ampicillin derived from Hetacillin after administration of the latter to a total of 61 rats classified in 7 groups were determined. Each of these groups was pre-treated for 15 days with the following inducers; phenobarbital, diphenylhydantoin, diazepam, chlorpromazine and phenylbutazone. The control group received saline. The d-glucaric acid concentration in the urine prior to and after the administration of inducers and the liver weight were taken as enzyme induction indices. Results showed a positive correlation between the indices of induction and the levels of ampicillin originating from hetacillin with a significant correlation coefficient between the serum levels of ampicillin and urine d-glucaric acid for all drugs studied. The different effect of the various drugs indicated that they could be classified into the following two groups: a) those that induced a significant increase of the levels and half life (t1/2) of ampicillin. The effect was significant in decreasing order for phenylbutazone (r = 0,990), diazepam (r = 0,990) and diphenylhydantoin (r = 0,753). b) those which initially resulted in a significant increase of the levels of ampicillin and thereafter in a decrease with a significant shortening of its t1/2 too. The effect was most significant for phenobarbital (r = 0,887) and less so for chlorpromazine (r = 0,800). Only for these two drugs was a significant and actually negative correlation observed between d-glucaric acid and t1/2 that is: phenobarbital (r = -0,967) chlorpromazine (r = -0,752). Results suggest an interaction of Hetacillin and the above inducers.

Intrarenal concentrations of ampicillin in acute pyelonephritis

The intracortical, medullary, and papillary distribution of ampicillin was studied in normal and pyelonephritic rats. At 4 days after induction of pyelonephritis, the animals were given a single injection of 100 mg of ampicillin per kg or were treated for 1 week with two daily doses of 100 mg/kg. Major differences in the intrarenal distribution of ampicillin were noted between normal and pyelonephritic animals. At 2 hours after injection, the concentrations of ampicillin in all parts of the infected kidneys were significantly lower (P less than 0.05) than in normal kidneys. The area under the curve (micrograms.minute per milliliter) over a 4-h period after single injection was much lower in the medulla (6.3 +/- 0.9) and papilla (29.6 +/- 4.2) of infected kidneys than in the medulla (11.2 +/- 1.6) and papilla (44 +/- 10.1) of noninfected kidneys. Whereas the ratio of concentration in tissue to concentration in serum ranged to 11.1 in the papilla of normal animals, this ratio was reduced to 2.4 in the presence of pyelonephritis. The diminution of the concentration gradient was also striking in the urine, where there was a reduction of more than threefold in pyelonephritic animals. One week of therapy resulted in a noticeable reduction of the inflammatory process associated with a return to near-normal intrarenal distribution of ampicillin. In normal rats treated with multiple doses, there were decreases of the antibiotic concentrations in serum and kidneys and in the area under the curve for these tissues.

Antibacterial active components in human urine after administration of penicillins

Four-hourly urine from volunteers and patients who had received penicillins orally or intravenously was investigated by means of thin layer chromatography and bioautography. Antibacterially active metabolites were not detected with only two of 12 penicillins, namely amoxicillin and mezlocillin. In the case of the other penicillins the metabolites possessed variable antibacterial activity as could be demonstrated using different test microorganisms. After administration of carbenicillin esters three antibacterially active spots were detected, one of which corresponded to penicillin G; the other two were active against Pseudomonas aeruginosa. The bioautogram after treatment with azlocillin showed two components which were active against Bacillus subtilis, Staphylococcus aureus and Escherichia coli; only the rapid moving component was active against P. aeruginosa, however. The formation and chemical nature of these additional active components is still to a large extent not understood. It is quite possible, however, that they affect the bio-availability of an antibiotic.

Active metabolites of isoxazolylpencillins in humans

Metabolites of the isoxazolylpenicillins that still possessed antibacterial activity were shown to be present in urine and serum. In healthy subjects, the amounts excreted in urine were low; 10 to 23% of the excreted penicillin activities represented the metabolites. The highest amount of metabolite in urine was found for oxacillin, and the lowest was found for flucloxacillin. No extreme differences in the amounts of metabolite excreted were observed when the compounds were administered orally or intravenously. In one healthy subject metabolite levels were estimated for cloxacillin in serum. Very low levels were found, i.e., about 9% of the activity. In subjects with highly impaired renal function, the metabolite may represent up to 50% of the total level of penicillin in serum. The antibacterial activities of the different metabolites were of the same order of magnitude as those of the respective parent compounds. Also, the activity against benzylpenicillin-resistant staphylococci was retained. It is not likely that the formation of the active metabolites should influence therapeutic results.

On the absorption and metabolism of 35S-ampicillin

An aqueous solution of 35S-ampicillin and polyethylene glycol (PEG 4000, unabsorbable marker) was administered orally to 6 healthy subjects with gastrointestinal tubes. The minimal absorption of radioactive material, as shown by urinary excretion of label, differed markedly between subjects and averaged 44% (25-67). As the mean cumulative uptake in the proximal jejunum was 31% (24-45), it appeared that some of the radioactivity had been taken up in more distal parts of the gastrointestinal tract. Chromatographic fractionation of gastrointestinal aspirates indicated that more than 95% of the label usually remained attached to the parent compound. The corresponding figure for radioactive material recovered from urine was about 80-85%. A similar degree of decomposition was also found for label excreted in the urine of an additional subject who received 35S-ampicillin intravenously. In this experiment the urine contained 87% of the administered radioactivity.