Penicillin concentration in saliva and its influence on bacterial interference

The aim of the investigation was to study the influence of various penicillin levels on the interference between alfa- and beta-streptococci based on antibiotic levels registered after oral intake of penicillin tablets. It was found that penicillin was released from ordinary sugar coated tablets already in the mouth resulting in concentrations in saliva above the MIC of most penicillin sensitive microorganisms during the first 2 min. This was followed by a decrease of the alfa-streptococcal flora. It was also shown that penicillin levels above the MIC of alfa-streptococci resulted in prolonged survival of beta-streptococci as compared to that noted at penicillin levels above the MIC of beta-streptococci but below that of the alfa-strains. At this latter level a synergistic effect between penicillin and interfering alfa-streptococcal strains could be demonstrated.

Effect of ingesta on systemic availability of penicillins administered orally in dogs

Six penicillin preparations were administered to six dogs of various types, both when the dogs were fasted and when fed a standard meal immediately before dosing. The preparations used were: amoxycillin tablets and drops, ampicillin tablets, penicillin V tablets, phenethicillin tablets and cloxacillin capsules. A Latin square design was employed with ampicillin and the two amoxycillin preparations, while three separate cross-over studies were done with penicillin V, phenethicillin and cloxacillin. Dose rates used were 50 mg/kg for cloxacillin, and 10 mg/kg for the others. A microbiological method was used to assay penicillin in blood samples taken at intervals after dosing. Values for peak plasma drug concentration (Cmax), the time at which it occurred (Tmax), and area under the curve (AUC) were obtained for each curve of drug concentration plotted against time. In fasted dogs, ampicillin showed poorer systemic availability than did amoxycillin, with Cmax and AUC values of less than half those of amoxycillin. The solid and liquid preparations of amoxycillin had similar bioavailability. Ingesta adversely affected the systemic availability of antibiotic from all preparations tested. With ampicillin and both amoxycillin preparations, there were reduced Cmax and AUC and prolonged Tmax, indicating slowed and diminished absorption. Feeding did not alter Tmax with the other drugs, but reduced the Cmax of penicillin V, phenethicillin and cloxacillin and the AUC of cloxacillin. It is suggested that, if minimal impairment of bioavailability by ingesta is desired, then the penicillins commonly administered by mouth (amoxycillin, ampicillin, penicillin V, phenethicillin, cloxacillin) should be given to dogs that are fasting.

Uptake of benzylpenicillin, cefpiramide and cefazolin by freshly prepared rat hepatocytes. Evidence for a carrier-mediated transport system

The kinetics and mechanism of the hepatic uptake of beta-lactam antibiotics were studied by using freshly prepared rat hepatocytes. The initial uptake rates of benzylpenicillin and cefpiramide represented both saturable and nonsaturable transport processes, whereas that of cefazolin showed an apparently nonsaturable uptake process within the concentration range below 4 mM. The apparent nonsaturable uptake rate constants for benzylpenicillin, cefpiramide and cefazolin were 0.580, 0.047 and 0.289 nmoles/min/mg protein/mM respectively. The apparent values of Kt and Vmax describing the saturable transport were 0.473 +/- 0.158 mM and 2.02 +/- 0.48 nmoles/min/mg protein for benzylpenicillin and 0.847 +/- 0.254 mM and 0.70 +/- 0.18 nmoles/min/mg protein for cefpiramide respectively. The Arrhenius plot of benzylpenicillin uptake of 200 microM presented a single straight line in the range of 22 degrees-37 degrees with an activation energy of 16.8 kcal/mole. An energy requirement was also demonstrated for benzylpenicillin uptake as metabolic inhibitors (antimycin A, NaCN, rotenone and 2,4-dinitrophenol) significantly reduced the initial uptake rate of benzylpenicillin (P less than 0.05). Uptake of benzylpenicillin (200 microM) was not inhibited by ouabain (1 mM). Benzylpenicillin uptake was inhibited competitively by phenoxymethylpenicillin, cefpiramide and cefazolin with the inhibition constants, Ki, of 0.680, 0.583 and 11.7 mM respectively. Benzylpenicillin also inhibited competitively the uptake of cefpiramide with a Ki of 0.655 mM. From these results it was considered that a carrier-mediated uptake system participates in the hepatic uptake of at least four of the beta-lactam antibiotics examined in this study.

Pharmacokinetics of phenoxymethylpenicillin in tonsils

The pharmacokinetics of phenoxymethylpenicillin in tonsillar tissue was studied in 33 patients who underwent tonsillectomy, mainly because of repeated tonsillitis or peritonsillitis. The patients were operated on 30-240 min after an oral penicillin dose of 12.5 mg/kg body weight. The mean serum concentration was 2.8 micrograms/ml for 10 patients operated upon 80-95 min after drug administration. The mean tissue concentration for these patients at the same time was 0.6 micrograms/g. The mean concentration of penicillin in tissue after 240 min was 0.05 micrograms/g. 19% of the serum concentration was recovered in the tonsillar tissue. No significant difference between penicillin concentration in the centre or surface of the tonsils was found. The tissue concentration was calculated to be above 0.03 micrograms/ml for at least 4-5 h. 30% of the patients harboured penicillinase producing bacteria on their tonsils, mainly Staphylococcus aureus. These patients had a lower tissue concentration than those lacking the bacteria, but the difference was not statistically significant (p = 0.095).

Molecular cloning of Bacillus sphaericus penicillin V amidase gene and its expression in Escherichia coli and Bacillus subtilis

The Bacillus sphaericus gene coding for penicillin V amidase, which catalyzes the hydrolysis of penicillin V to yield 6-aminopenicillanic acid and phenoxyacetic acid, has been isolated by molecular cloning in Escherichia coli. The gene is contained within a 2.2-kilobase HindIII-PstI fragment and is expressed when transferred into E. coli and Bacillus subtilis. The expression in B. subtilis carrying the recombinant plasmid is approximately two times higher than in the original B. sphaericus strain. A comparison of the purified enzyme from B. sphaericus and the expressed gene product in E. coli minicells suggests that the native enzyme consists of four identical subunits, each with a molecular weight of 35,000.

Bactericidal activity of phenoxymethylpenicillin in an in-vitro model simulating tissue kinetics

The antibacterial efficacy of phenoxymethylpenicillin (Pen-V-K) against strains of Staphylococcus aureus was assessed in an in-vitro kinetic model. Simulation was based on human serum levels and tissue water curves obtained after a single oral dose of 392.2 mg of the drug. Differences in bacterial elimination kinetics were noted depending upon the type of curve (serum or tissue water) being simulated.

Absorption of oral penicillin before and after gastroplasty for morbid obesity

Gastroplasty for morbid obesity results in a small proximal pouch with a narrow stoma to the distal stomach. Absorption of phenoxymethylpenicillin given in tablets and liquid form was evaluated in 8 females before and 3 months after gastroplasty. Penicillin absorption was not affected to any significant extent. Oral penicillin can therefore safely be given for the treatment of infections in patients after gastroplasty.

[Properties of acylase preparations from an actinomycete culture]

A comparative study of some physico-chemical properties of high-purified preparations of extracellular penicillin-V-acylase and aminoacylase, isolated from the actinomycete Streptoverticillium No 62, revealed the difference in pH and temperature optima, in the sensitivity to the ionic composition of buffer solutions, in the enzyme stability during storage. As for the aminoacylase preparation, its thermostability was studied at different pH values, as well as the effect of specific compounds was tested. Similar to other fungal enzymes, the aminoacylase possesses a wide substrate specificity, and by its stereospecificity can be related to L-aminoacylases, while penicillin-V-acylase is a high-specific enzyme, active against phenoxymethylpenicillin.

Effect of guar gum, a fibre preparation, on digoxin and penicillin absorption in man

The effect of guar gum on the absorption of digoxin and phenoxymethyl penicillin was studied in a double blind study in 10 healthy volunteers. Guar gum reduced serum digoxin concentration during the early absorption period, but a similar amount of digoxin was found in 24 h urine whether given with or without guar gum. Both the peak penicillin concentration and the area under the serum curve were significantly reduced by the gum.

Absorption of phenoxymethylpenicillin from mixtures and tablets in healthy volunteers

The absorption of the potassium, calcium and benzathine salts of phenoxymethylpenicillin, given as mixtures, was investigated in twelve healthy volunteers. The potassium salt gave the fastest and highest serum peak levels. Also the relative bioavailability of the potassium salt was greatest, as indicated by the areas under the serum concentration/time curves (AUC). In a second study with twelve other volunteers, the absorption of the mixtures and tablets of the potassium salt was studied. The peak serum levels and AUC were comparable after these preparations. The results in our two studies indicate that, from a pharmacokinetic point of view, the potassium salt of phenoxymethylpenicillin in mixtures should be preferred in clinical practice. It also appears that the absorption of phenoxymethylpenicillin from the tablets and mixtures of the potassium salt is comparable, giving the same relative bioavailability.

[Antibacterial concentrations in serum and tooth-jawbone tissue following perioperative administration of propicillin]

Antibacterial Concentrations in Serum and Dental Tissues after Preoperative Application of Propicillin. After resecting radicular and follicular cysts in the jaws, the serum, bone, capsule and fluid of the cysts from 40 patients were studied for their propicillin concentration. The patients received 1 Mega unit (0.7 g) propicillin orally as oblong tablets one or two hours before surgery. One or two hours after the application of propicillin, the distribution coefficients between serum and the three tissues were 0.78 and 0.87 for the spongious bone, 0.07 and 0.06 for the cyst capsule and 0.14 and 0.08 for the cyst fluid. The mean concentrations in all three tissues were distinctly above the MICs of the bacteria most frequently isolated from the mouth for at least two hours.

Phenoxymethyl penicillin in the horse: an alternative to parenteral administration of penicillin

This preliminary study evaluated phenoxymethyl penicillin (Penicillin V) as an alternative to parenteral administration of penicillin in horses. Penicillin V was administered orally to five horses at two different doses and plasma levels of the drug were determined at timed intervals. The results were evaluated by regression analysis. Following the administration of penicillin V at a dose of 66,000 IU/kg or 110,000 IU/kg, the mean peak plasma levels obtained were 1.55 micrograms/mL and 2.34 micrograms/mL respectively. A plasma level two to four times above the minimal inhibitory concentration level of Streptococcus equi and Streptococcus zooepidemicus was maintained for 325 minutes at 66,000 IU/kg and 349 minutes at 110,000 IU/kg. Penicillin V given orally was thus shown to be an acceptable alternative to parenteral administration of penicillin in the horse.

Absorption and distribution patterns of oral phenoxymethyl penicillin (penicillin V) in the horse

Serum levels of phenoxymethyl penicillin (penicillin V; Pen V) were measured following oral administration of two different formulations of the drug to five healthy horses. The mean serum concentration profile was described by a two-compartment model with a first order rate of absorption. Half-lives of the absorption, distribution and elimination phases were, respectively, 0.199 +/- 0.035, 0.362 +/- 0.060 and 3.650 +/- 0.575 hours. The distribution of the drug to body fluid compartments other than serum was examined. Mean peak levels of Pen V in serum, synovial fluid, peritoneal fluid and urine were, respectively, 2.38 +/- 0.18, 0.35 +/- 0.02, 0.25 +/- 0.06 and 472 +/- 80 micrograms/ml with times to achieve peak concentration ranging from 30-360 minutes after oral administration. Steady state pharmacokinetic measurements predicted that minimum serum Pen V concentrations of 0.1 micrograms/ml would be maintained by oral administration of the drug (110,000 I.U./kg) at 8 hour intervals. Our data indicate that oral Pen V is a feasible approach to long-term penicillin therapy in the equine patient.

Effects of surfactants on the GI absorption of beta-lactam antibiotics in rats

The effects of various nonionic and ionic surfactants and two bile salts (sodium cholate and sodium taurocholate) on the GI absorption of beta-lactam antibiotics were investigated using the in situ rat GI perfusion technique. Addition of 10 mM polyoxyethylene-23-lauryl ether in the perfusion solution reduced the absorption of propicillin by the stomach and markedly increased the absorption of propicillin and cefazolin by the small intestine. Ester-type nonionic surfactants and bile salts exerted no significant influence on the intestinal absorption of these antibiotics.

Concentration of penicillin in nasopharyngeal secretions

The penicillin concentration in the nasopharyngeal secretion after penicillin administration was studied in 33 patients undergoing tonsillectomy. Benzylpenicillin was either administrated by the intravenous or the intramuscular route in doses of 0.6-1.2 g. Phenoxymethylpenicillin was given perorally in doses of 0.5-1.0 g. The secretion from the nasopharynx was collected prior to the operation both in a disposable collector and on a filter paper disc. A serum sample was also drawn prior to and immediately after the operation. The serum penicillin concentration reached levels of 16.0 mg/l, 5.8 mg/l and 3.6 mg/l (mean values) when given by the intravenous, the intramuscular and the peroral route, respectively. The mean penicillin concentration in nasopharyngeal secretion was 1.6 mg/l, 0.3 mg/l and 0.3 mg/l for these three administration modes. In the majority of cases the concentration of penicillin in the nasopharyngeal secretion exceeded the minimum inhibitory concentration for Streptococcus pneumoniae (0.006-0.12 mg/l).

The influence of the sweetening agent on the oral absorption of penicillin V

Plasma concentrations of Penicillin V were determined following oral administration in children of mixtures containing different sugars as sweetening agents. Significantly higher peak plasma concentrations and area under the curve were found with sacharose than with sorbitol. Mixtures containing fructose gave intermediate values.

Bioavailability of paediatric mixtures containing phenoxymethylpenicillin calcium or potassium salt

The bioavailability of the calcium and potassium salts of phenoxymethyl-penicillin (dose 38,000 I.U./kg) was investigated in eight healthy adult volunteers. Administration of the calcium salt as an aqueous oral mixture resulted in a mean peak plasma concentration of 8.52 mg/l (SD 1 X 96) and that of the potassium salt mixture in a concentration of 8.40 mg/ml (SD 2.61), p greater than 0.1. The median time-to-peak levels were 0.75 h and 1.0 h, respectively (p greater than 0.1). The mean AUC for the calcium salt mixture was 16.94 mg X h/l (SD 3.31) and for the potassium salt 15.84 mg X h/l (SD 4.76), p less than 0.09. These findings confirm that an aqueous mixture of calcium phenoxymethylpenicillin is equivalent to a mixture of potassium phenoxymethylpenicillin.

Absorption of penicillin and paracetamol after small intestinal bypass surgery

Drug absorption was studied in morbidly obese patients before and after jejunoileal bypass. The absorption of phenoxymethyl penicillin was considerably increased whilst that of paracetamol was unchanged.

Pharmacokinetics of phenoxymethylpenicillin in volunteers

Pharmacokinetics of phenoxymethylpenicillin was studied in 12 healthy volunteers. They received four different single oral dose sizes. At all dose levels (0.4, 1, 2 and 3 g) phenoxymethylpenicillin was rapidly absorbed, usually with serum peaks within 0.75 h. The mean maximal serum peaks (+/- SD) were 6.1 +/- 2.0, 15.0 +/- 4.3, 26.3 +/- 10.0 and 35.5 +/- 10.8 mg/l after 0.4, 1, 2 and 3 g, respectively. The relationship between the mean peak serum concentrations and the doses was nonlinear (p less than 0.001). The mean areas under the serum concentrations vs. time curve (AUC) increased almost linearly with increasing doses, and the deviation from linearity was not significant (p less than 0.05). Very low penicillin concentrations were obtained in saliva. The urinary excretion during 10 h was 37--43% of the doses given. The pharmacokinetic results indicated that phenoxymethyl penicillin in the present formulation is rapidly and well absorbed up to as high doses as 3 g. The tablet formulations used were better absorbed than previous ones. The percent of absorption was relatively lower with the highest doses, but this probably has only minor therapeutic consequences.

The effect of food on the oral absorption of penicillin V preparations in children

The oral absorption of pc V in different preparations, given at various times before and after a meal, was investigated in children with upper respiratory infections. The best absorption with respect to peak concentration was observed when potassium pc V (Calciopen) was given after at least two hours of fasting with no food intake within the following hour. Shorter periods of fasting (1, 1/2, 0 hrs) before drug intake resulted in significantly lower plasma concentrations. When drug intake was followed by a meal, the absorption was also decreased to some extent. When pc V was given in an oil suspension (Fenoxypen), or in a small volume (Roscopenin) together with a meal, the peak concentration was significantly lower than when pc V was given in an aqueous solution with a larger volume (Calciopen).

Active phenoxymethylpenicillin (pcV) in the mucous membranes of the oral bucca and maxillary sinus and in diffusion chambers implanted in rabbits. A methodological study

The intention of prescribing antibiotic treatment must be to achieve a concentration of the agent within the infected tissue well above th MIC or the bacteria causing the infection. As a basis for further clinical studies on antibiotic concentrations in maxillary sinus mucosa in humans, determinations of biologically active penicillin V in the mucous membranes of the maxillary sinus and the buccal mucose as well as in tissue fluids and tissue from subcutaneously implanted tissue cages in rabbits were made. Several experimental conditions were studied, with the purpose of establishing optimal conditions with regard to tissue sampling, blood contamination, prediffusion time, etc. Penicillin V was shown to have a good penetration into mucosal tissue in the rabbit, even at low perfusion pressure.

Absorption of penicillin V from mixture formulations. Comparison of potassium and benzathine salts

The absorption rate and serum level curves of two commercial phenoxymethylpenicillin mixture preparations were compared in adult volunteers. Both the potassium salt (Primcillin) and the benzathine salt (V-Pen ped forte) of V-penicillin were rapidly absorbed and the mean peak serum levels were obtained with both preparations within the first hour after single dose administration. The mean peak level obtained with the potassium salt was several-fold higher (p less than 0.001) and was also reached within a shorter time than that of the benzathine preparation. These results confirm the earlier evidence, obtained with other formulae, for the superior bioavailability of the potassium salt of V-penicillin as compared to most other derivatives used in V-penicillin mixtures.

Levels of antibiotic in human blood and interstitial fluid after oral administration of bacampicillin or phenoxymethyl penicillin and intravenous administration of amoxicillin or ampicillin

Levels of antibiotic in the serum and interstitial fluid were determined for 11 volunteers who received conventional doses of either phenoxymethyl penicillin (penicillin V) or bacampicillin orally and for 11 volunteers who received either amoxicillin or ampicillin intravenously. The levels of antibiotic achieved in both blood and interstitial fluid were higher in the volunteers who received bacampicillin than in those who received penicillin V. The levels of antibiotic in serum and interstitial fluid of participants in the study who received amoxicillin or ampicillin intravenously were comparable with those achieved with equivalent doses of oral bacampicillin. The lowest levels of antibiotic in serum and interstitial fluid were obtained in volunteers who received oral penicillin V, whereas the highest levels were obtained in those given ampicillin and amoxicillin intravenously.

Concentration of penicillin V in serum and middle ear exudate during treatment of acute otitis media

Sixty-one patients, aged six months to ten years, with acute purulent otitis media were treated with penicillin V for ten days. The drug was given twice a day in a total daily dose of 50 mg/kg body weight. The concentration of penicillin was determined in serum and in middle ear exudate on one of the first six days of treatment, 60, 120 or 180 minutes after administration of the drug. Bacterial cultures were taken from the nasopharynx before and during treatment and from the middle ear exudate at the time of myringotomy. The serum level of penicillin decreased during treatment. There was also a decrease in penicillin concentration of the middle ear exudate during treatment. This decrease was most pronounced during the first two days. In a few cases Haemophilus influenzae was found in the middle ear exudate during treatment. In these cases the concentration of penicillin in the exudate was found to be higher than the mean concentration at corresponding times. The rapid decrease in the exudate concentration of the drug two to three days after the beginning of therapy may suggest that the patients responded to the treatment and that it is the initial concentration that decides whether an infection will respond to the therapy. High exudate concentrations later on seem to be due mainly to a continuation of the inflammatory reaction and had slight or no clinical effect. Thus, the present investigation produced no strong evidence for a ten-day treatment compared with, for example, a five-day treatment.

GI absorption of beta-lactam antibiotics II: deviation from pH--partition hypothesis in penicillin absorption through in situ and in vitro lipoidal barriers

The absorption of propicillin from the rat stomach and small intestine in situ was examined as a function of recirculating solution pH. The in vitro interphase transport from an aqueous buffer of various pH values to the octanol phase was also studied for several penicillins by the use of a two-phase rolling cell. The rate--pH profiles obtained from both in situ and in vitro experiments deviated significantly from the dissociation curves. The degrees of the shifts were approximately 2 pH units for the in situ intestinal absorption of propicillin and in vitro transport of propicillin and cloxacillin, approximately 1.5 pH units for the in vitro transport of penicillin V, and 0.8 pH unit for the in situ stomach absorption of propicillin. These discrepancies from the classical pH--partition hypothesis can be interpreted by the permeation through the lipoidal barrier of the undissociated species of penicillins transported through the aqueous diffusion layer adjacent to the lipoidal surface. All in situ and in vitro experiments tend to support this theory.

Absorption of phenoxymethylpenicillin in children. The influence of age, state of disease and pharmaceutical preparation

The bioavailability of phenoxymethylpenicillin (pc V) was determined in children with upper respiratory infection (age 1 month-5 years) following the administration of different commercial preparations of pc V. Administration of potassium pc V in water solution resulted in a significantly higher plasma concentration than the same dose of potassium pc V in an oil vehicle. There was no difference in absorption between tablet and mixture (the water solution) when potassium pc V was given, but with calcium pc V lower plasma levels were found after the oil mixture form than after the tablets. The results indicate that the oil mixture form and not the type of salt is responsible for the decreased absorption observed after some preparations of pc V. The absorption of solutions of potassium and calcium pc V was also examined in two different age groups, 1--5 months and 6 months-5 years. For both preparations the younger children obtained higher plasma levels. In 4 children with coeliac disease a decreased absorption compared to control children was found of potassium pc V in solution and this was most pronounced when the oil vehicle was used.

[Acylase activity of mycophilic fungi]

The acylase activity was studied with 65 cultures of mycophilic fungi belonging to 56 species and 33 genera. Among these: 9 species displayed the acylase activity toward ampicillin; 8 species, toward phenoxymethylpenicillin; 6 species, toward benzylpenicillin; and 21 species manifested the complex activity. Many of the active species belonged to the bionecrotrophic group of mycophilic fungi, the number of necrotrophic fungi was less, while that of biotrophs and saprotrophs was even lower.

The gastrointestinal absorption of penicillin V in children with suspected coeliac disease

The gastrointestinal absorption of penicillin V (pc-V) was investigated in 6 children, 6-12 months old, with suspected coeliac disease. The diagnosis was set after small bowel biopsy and absorption tests of vitamin A and d-xylose. As control groups served 7 children with diarrhoea but with normal small bowel biopsy and/or absorption tests and a group of 9 children with upper respiratory tract infection of the same ages as the children in the test group. The absorption of calcium pc-V in oil suspension (Penicals) was impaired in the patients with suspected coeliac disease compared to that of the control groups. There was no significantly different absorption of pc-V between the control children with diarrhoea and those with upper respiratory tract infection. After 6-8 months of gluten free diet in the children with suspected coeliac disease their absorptive ability of oral calcium pc-V in suspension form was equal with that of a control group.

The bioavailability of oral penicillin V. A comparative study of the absorption of different salts of penicillin V in children

Different salts of penicillin V (pc-V): potassium pc-V (Calciopen and Kåvepenin), calcium pc-V (Penicals) and benzathine pc-V (Meropenin) were given to 37 children (age 2 months to 4 years) with upper respiratory infections. The gastro-intestinal absorption of the drug given in a mixture was followed for three hours after administration by determination of the serum levels from capillary samples. Administration of the mixtures containing the potassium pc-V resulted in a more rapid absorption and in significantly higher plasma concentrations at 30 min than did administration of the preparations containing the calcium and benzathine salts. In four children with coeliac disease, verified by intestinal biopsy, the absorption of potassium pc-V (Calciopen) was compared with that of calcium pc-V (Penicals). A decreased absorption was found and this was most pronounced when the calcium salt was given.

[Bioavailability of different brands of phenoxymethylpenicillin (author's transl)]

The bioavailability of 11 brands of phenoxymethylpenicillin was investigated in a cross-over-study in healthy volunteers. There were found some differences in the velocity of absorption, in the peaks and in the blood levels after 4 hours. The absorption rate was evaluated by comparison of area under the curve and urine-recovery after oral administration of different brands. It is suggested to control each brand of oral antibiotic preparations on bioavailability.

Interaction between the exocellular DD-carboxypeptidase-transpeptidase from Streptomyces R61, substrate and beta-lactam antibiotics. A choice of models

The interaction between the exocellular DD-carboxypeptidase-transpeptidase of Streptomyces R61 and beta-lactam antibiotics is a multistep process during which a rather stable enzyme - antibiotic complex is formed. This mechanism of interaction is compatible with Lineweaver-Burk plots that are typical of a competitive inhibition of the hydrolysis of the peptide donor by the antibiotic. In fact, however, the same Lineweaver-Burk plots can be obtained on the basis of a non-competitive type of inhibition. At present, a choice between the two models cannot be made.

[Penicillin V potassium in tonsillar tissue and serum (author's transl)]

1.2 mega U Penicillin V potassium was given to 20 patients 2 hours (group 1) and another 19 patients 3 hours (group 2) before tonsillectomy. After the operation biological determinations of the levels of active principle were made from tonsillar tissue and serum with statistical evaluation of the results (Spearman's rank correlation). There was a significant connection between the serum and tonsillar tissue concentrations (in children and adults) in both groups. The level of the active principle in group 2 was only slightly lower than in group 1. Many of the micro-organisms responsible for tonsillitis can be influenced by the concentrations found here, so that application of Penicillin V can often be expected to have a good therapeutic effect.

[Identification of the beta lactamase R-TEM of Pseudomonas aeruginosa]

This paper is dealing with the enzymatic problem raised by two strains of Ps. aeruginosa resistant to classical beta lactam antibiotics including carbenicillin. These two strains hydrolyse all these antibiotics. In both cases, we have shown the simultaneous biosynthesis of two enzymes: an inducible and chromosome cephalosporinase frequently found in this germ, and a constitutive beta lactamase, with a penicillinase activity which has been identified with the extrachromosomic beta lactamase R-TEM. These two enzymes have been separated by affinity chromatography, characterized by their kinetic constants given by computerized microacidimetry, and their isoelectric points which are respectively 9.2 for the cephalosporinase and 5.40 for the penicillinase R-TEM. Isoelectric focussing also shows the separation of these two enzymes.

Oral absorption efficiency of acid-labile antibiotics from lipid-drug delivery systems

The utility of cholesterol, cholesteryl acetate, and beta-sitosterol in protecting and improving the oral absorption efficiency of acid-labile antibiotics is discussed. The potassium salts of penicillin G and penicillin V and erythromycin lactobionate were studied. The stability of the two penicillins in simulated gastric fluid was determined iodometrically. The rank order of acid protective activity was: cholesteryl acetate greater than beta-sitosterol greater than cholesterol. Oral administration of erythromycin lactobionate coated with cholesteryl acetate produced a twofold increase in human urinary excretion of erythromycin when compared with the uncoated material. Potassium salts of penicillin G and penicillin V coated with cholesteryl acetate yielded 1.6- and 2-fold higher urine levels, respectively, as compared with the uncoated candidates.