Intracellular accumulation and activity of ampicillin used as free drug and as its phthalimidomethyl or pivaloyloxymethyl ester (pivampicillin) against Listeria monocytogenes in J774 macrophages.

AIMS: To determine the intracellular accumulation in a macrophage cell line of ampicillin and ampicillin esters, and to measure their activity against intracellular Listeria monocytogenes. METHODS: Quantitative evaluation of the activity of ampicillin, phthalimidomethylampicillin (PIMA) or pivaloyloxymethylampicillin (PIVA) against intracellular L. monocytogenes, and direct measurement of cellular ampicillin concentration in J774 macrophages. RESULTS: Ampicillin, PIMA and PIVA caused a 0.5 log decrease in cell-associated cfu within 5 h when used at an extracellular concentration of 3.6 microM [10 x MIC of ampicillin (1.25 mg/L); 1.83 mg/L for PIMA and 1.67 mg/L for PIVA]. Addition of beta-lactamase in the extracellular milieu abolished the activity of ampicillin and of PIMA but not that of PIVA. At low extracellular concentrations [0.5 x MIC ampicillin (62.5 microg/L); equimolar concentrations for PIMA (91.5 microg/L) and PIVA (83.5 microg/L)], ampicillin and PIMA lost all activity (compared with controls), but PIVA remained as active as at the higher concentration. Incubation of cells with PIVA at the low concentration (83.5 microg/L) for 20 h caused a 2 log reduction of cfu if the medium was changed every 5 h (to compensate for the degradation of extracellular PIVA). Incubation of cells with PIVA allowed for a marked (four- to 25-fold) cell accumulation of ampicillin, whereas no ampicillin accumulation was seen for cells incubated with ampicillin or with PIMA. CONCLUSIONS: This is the first demonstration that PIVA (a prodrug of ampicillin) can be used to promote ampicillin cellular accumulation and, thereby to increase ampicillin intracellular activity. PIVA could be useful for control of the intracellular multiplication of L. monocytogenes.

Distribution of penicillins into subcutaneous tissue chambers in ponies.

The distribution of penicillins into a tissue chamber implanted subcutaneously in ponies was studied. Ampicillin sodium (equivalent to 15 mg/kg ampicillin) was administered intravenously. Pivampicillin, a prodrug of ampicillin, was administered by nasogastric tube to fed ponies at a dose of 19.9 mg/kg (equivalent to 15 mg/kg ampicillin). Procaine penicillin G was administered intramuscularly at a dose of 12 mg/kg (equivalent to 12000 IU/kg). Six ponies were used for each medication. Antibiotic concentrations in plasma and tissue chamber fluid (TCF) were measured for 24 h after administration. Mean peak concentrations of ampicillin in TCF were 7.3 micrograms/mL, reached at 1.7 h, and 1.3 micrograms/mL, reached at 2.7 h, after administration of ampicillin sodium and pivampicillin respectively. The mean peak concentration of penicillin G of 0.3 microgram/mL was reached 12.3 h after administration of procaine penicillin G. Concentrations in TCF remained above the minimum inhibitory concentration of Streptococcus zooepidemicus for the proposed dosing intervals of 8, 12 and 24 h for ampicillin sodium, pivampicillin and procaine penicillin G respectively.

Formation of pivaloylcarnitine in isolated rat heart cells.

Pivaloyl-containing antibiotics and pivalic acid in man or rat have been reported to cause increased urinary carnitine loss secondary to pivaloylcarnitine generation. Pivaloylcarnitine concentration was especially high in heart after administration of pivalic acid or pivampicillin in vivo. Formation of pivaloylcarnitine was therefore studied in isolated rat heart cells in the presence of sodium pivalate. Formation of pivaloylcarnitine in rat heart cells increased with incubation time, after a lag time from 0 to 2 h and linearly up to 6 h. The formation increased with increasing concentration of sodium pivalate, followed Michaelis-Menten kinetics with an apparent Km = 348 +/- 10 microM and Vmax = 116 +/- 20 pmol.mg protein-1.h-1. Bromoacetylcarnitine inhibited the pivaloylcarnitine formation to Ki = 116 +/- 43 microM and Vmax = 107 +/- 14 pmol.mg protein-1.h-1. The uptake of carnitine in heart cells was suppressed 62-74% by deoxycarnitine (40 microM) and D-carnitine (200 microM), and 95% by NaF (5 mM), NaN3 (500 microM) or at temperature 4 degrees C. Pivaloylcarnitine inhibited carnitine uptake to 33-35% of the controls, while sodium pivalate did not. More than 90% of intracellular pivaloylcarnitine was released from the heart cells after 18 h of incubation in the absence of sodium pivalate and L-carnitine. These data show that pivalate is readily converted to pivaloylcarnitine in heart cells, in contrast to the limited conversion in hepatocytes.

Carnitine content of red blood cells of human subjects treated with pivampicillin and carnitine.

Total- and free carnitine content of washed pooled red blood cells collected from five children prior to and on the last day of combined pivampicillin and equal molar carnitine treatment were measured. On the last day of treatment (day 7) the level of total carnitine decreased from 47.5 +/- 3.39 to 37.5 +/- 2.48 nmol/ml, mean +/- SEM (p less than 0.05) with a concomitant decrease of free carnitine (from 19.2 +/- 0.97 to 15.5 +/- 0.99 nmol/ml, p less than 0.05) as compared with the pretreatment control day (day 0). The calculated amount of acid soluble carnitine esters also fell (from 28.2 +/- 3.38 to 21.9 +/- 1.78 nmol/ml). The same effects were found when the carnitine levels were referred to haemoglobin or water content of samples. These results demonstrate that in pivampicillin treatment the carnitine pool of erythrocytes also alters. In agreement with previous findings the data presented here suggest, that the administered carnitine was not sufficient to meet the enhanced needs of the organism caused by the pivalate load and that the organism utilized some of its stores for pivaloylcarnitine production. The decreased carnitine ester level of erythrocytes suggest, that the red blood cells do not participate in significant extent in pivaloylcarnitine transport or production.

Differential excretion of xenobiotic acyl-esters of carnitine due to administration of pivampicillin and valproate.

The fate of supplemental carnitine was studied in human subjects treated with drugs known to cause carnitine deficiency. Six children were treated with pivampicillin and equimolar L-carnitine for 7 days. On the last day of treatment, the plasma levels of total and free carnitine were decreased, but acylcarnitine levels were increased. A 12-fold increase in urinary excretion of acylcarnitines was found; it increased from 188.5 +/- 82.7 to 2218.4 +/- 484.1 mumole/day, and 84% was pivaloylcarnitine. Free carnitine excretion was reduced. Ten epileptic children on chronic valproate treatment received equimolar carnitine for a 2-week period. Plasma carnitine levels were elevated on the last day of treatment. A 3.4-fold increase in urinary acylcarnitines was found, but most of the excreted carnitines were free (64.5-fold increases). These data show that pivalate is readily converted to carnitine esters, in contrast to the limited conversion of valproate to acylcarnitines in humans.

Ampicillin in breast milk during puerperal infections.

Low concentrations of ampicillin were found in colostrum/breast milk from 6 mothers treated with pivampicillin 1.05 to 2.1 g daily during the first to eighth day postpartum in the maternity ward. It was calculated that the breast-fed infant could theoretically receive 0.05-0.37% of the dose/kg given to the mother. It is concluded that direct exposure of the breast-fed infant suckling from a mother under treatment with ampicillin or pivampicillin seems to be minimal.

Kinetics and mechanism of enzymatic hydrolysis of pivampicillin monolayers.

A study of the enzymatic hydrolysis of pivampicillin (an insoluble penicillin) extended as a monolayer on the aqueous interface at a constant surface pressure has been performed. Penicillinase promotes intensive hydrolysis of the pivampicillin monolayers, inducing their solubility. However, no action was observed with dog liver esterase. The hydrolytic process, which was dependent on the film surface pressure and on the quantity of the injected enzyme, is of the Michaelis-Menten type in two dimensions.

Penetration of ampicillin ('Pondocillin') and amoxycillin ('Imacillin') into bronchial secretions.

The penetration of ampicillin and amoxycillin into bronchial secretions was investigated by bronchoscopy in 20 patients suffering from exacerbations of chronic bronchitis. Five patients received 500 mg pivampicillin, 8 received 700 mg pivampicillin and 7 received 500 mg amoxycillin. There were no significant differences between these three treatments in respect of the serum and bronchial secretion concentrations at the time of bronchoscopy, nor were there any significant differences in the peak serum level or total bioavailability of each regimen. The concentrations in bronchial secretions, on average, were 5.7%, 9.0% and 7.6% of the corresponding serum concentrations in patients given 500 mg pivampicillin, 700 mg pivampicillin and 500 mg amoxycillin, respectively. The concentration in bronchial secretions exceeded the MIC for sensitive strains of Haemophilus influenzae in more cases treated with pivampicillin than with amoxycillin.

Serum concentrations and penetration into prostate of mecillinam and ampicillin.

The absorption of the two antibiotic pro-drugs pivmecillinam and pivampicillin was investigated in 10 patients with normal or slightly impaired renal function. After a therapeutic dose of 200 mg pivmecillinam plus 250 mg pivampicillin, the mean peak concentration in serum was 2.3 micrograms mecillinam and 5.3 micrograms ampicillin per ml. The elimination half-life was approximately 2 hours for both antibiotics. Consequently, a ratio of 2:5 was maintained in serum during the excretion period and this ratio is within the range where optimal synergistic effect between the two antibiotics against many Gram-negative organisms is most likely to occur. Penetration of mecillinam and ampicillin into the prostate, determined in tissue homogenate obtained from 10 patients undergoing transurethral resection of the prostate showed that the antibiotics penetrated equally well with a serum tissue ratio of approximately 2:1.

The oral absorption of ampicillin, pivampicillin and amoxycillin in infants and children.

The oral absorption of comparable doses of mixtures of ampicillin, amoxycillin and pivampicillin was studied in 38 children from 6 months to 6 years of age. Plasma concentrations following pivampicillin and amoxycillin were higher than those following the administration of ampicillin. No significant difference was found between amoxycillin and pivampicillin. The oral absorption of pivampicillin mixture was further studied in 12 infants, 0-1 month and 1-5 months of age. The absorption was faster in infants and children more than 6 months of age than in the 1-5 months group. The excretion, indicated by the slope of the plasma concentration curve, was delayed in infants less than one month of age. The oral absorption of amoxycillin and pivampicillin from tablets was also studied in 12 infants and children, 6 months-6 years of age, in the same doses as when mixtures were studied and was more complete with pivampicillin than with amoxycillin. The absorption of pivampicillin was more complete from tablets than from mixture. Also with amoxycillin there was a trend towards more efficient absorption from tablet than from mixture.

Study of ampicillin levels in maternal serum, umbilical cord serum and amniotic fluid following administration of pivampicillin.

Premature rupture of the membrane is often followed by intrauterine infections. Antibiotic prophylaxis is recommended, but the effect has been debatable. Thirty pregnant women received pivampicillin 350 mg 4 times daily. The ampicillin levels in amniotic fluid and in the serum of the fetus and of the mother were determined and related to pivampicillin dose and time after administration. In the amniotic fluid the average concentration was 3.4 micrograms/ml, which is considered therapeutic. In maternal and fetal serum the ampicillin concentrations were low and took an almost parallel course. To obtain the same ratio between ampicillin serum levels and MIC (minimum inhibitory concentration) in the pregnant as in the non-pregnant subject, a double dosage should be used.

Pharmacokinetics of ampicillin and its prodrugs bacampicillin and pivampicillin in man.

Five healthy fasting male subjects were each given single doses of intravenous ampicillin (471 mg), oral ampicillin tablets (495 mg), oral bacampicillin hydrochloride tablets (562 mg ampicillin equivalent), and oral pivampicillin hydrochloride capsules (491) mg ampicillin equivalent) in a crossover experiment. The resulting concentrations of ampicillin were determined in plasma and urine. The pharmacokinetic analysis was made according to a two-compartment open model. The total distribution volume of unbound ampicillin during the disposition phase was 0.247 +/- 0.045 (SD) liter/kg, which is only slightly more than the extracellular fluid, suggesting that tissue binding and intracellular distribution of ampicillin are limited. The bioavailability of the esters bacampicillin (86 +/- 11%) and pivampicillin (92 +/- 18%) was significantly greater than that of ampicillin (62 +/- 17%); however, the difference between the esters was not statistically significant. The adsorption for all drugs given orally proceeded at a constant rate, suggesting zero-order release rates from the products. The adsorption rate was highest for bacampicillin (0.89 +/- 0.39 of dose absorbed per minute), followed by pivampicillin (0.64 +/- 0.19) and ampicillin (0.58 +/- 0.16). Bacampicillin also had the shortest lag time for the start of absorption (7.0 +/- 0.9 min) under the present conditions. Thus, in comparison with ampicillin, the esters have a higher bioavailability, which, in fact, is close to the theoretically highest possible value by clearance concepts. The higher bioavailability in connection with higher absorption rates may be clinically important in ampicillin treatment by the oral route.

A gastroscopic and pharmacological study of the disintegration time and absorption of pivampicillin capsules and tablets.

1 An in vitro investigation showed that pivampicillin tablets disintegrated more rapidly than pivampicillin capsules. This result was demonstrated and confirmed by gastroscopy in a cross-over study in healthy volunteers. 2 There were no differences in serum levels of ampicillin obtained with the two preparations, but compared with non-gastroscoped volunteers, there was delay of 0.5--1.5 h in the appearance of peak serum ampicillin concentrations after gastroscopy. 3 Half of the volunteers receiving pivampicillin capsules developed hyperaemia, interstitial bleeding or erosions of the gastric mucous membrane. No such reactions were seen after pivampicillin tablets. 4 In one volunteer, a pivampicillin capsule was trapped in a not previously noticed hiatus hernia and local changes and pain occurred.

[Bioavailability of orally administered antibiotics: influences of food on resorption (author's transl)]. / Resorptionsbeeinflussung oraler Antibiotika in Saftform durch Nahrungsmittel.

After the administration of a liquid suspension of Penicillin V-K, Epicillin, Cephalexin, Ampicillin, Pivampicillin and Amoxycillin on fasting and not fasting children, plasma levels and urine excretion of antibiotics were determined. A standard meal influences in Penicillin V-K and Ampicillin not only the maximum plasma levels, but also the absorbed amount of the drug. In Epicillin, Pivampicillin and Cephalexin we were not able to detect an influence of food on absorption. Amoxycillin doesn't seem to be impaired by food. However, the considerable individual differences could have its reasons in a number of other factors presently investigated.

Oral absorption of pivampicillin and ampicillin in young children: cross-over study using equimolar doses of a suspension.

In a cross-over study, the oral absorption following equimolar doses of ampicillin corresponding to 16.7 mg/kg administrered as pivampicillin ('Pondocillin') suspension and ampicillin ('Doktacillin') suspension respectively, was investigated in 11 children aged from 8 months to 4.5 years. Pivampicillin produced a mean peak serum concentration of 10.7 microgram ampicillin/ml compared with 5.8 microgram/ml after ampicillin. The mean area under the serum concentration-time curves was 29.2 microgram/ml-h after pivampicillin and 16.7 microgram/ml-h after ampicillin, reflecting the superior bioavailability of the ester form. In 4 of the children aged between 8 and 12 months, the serum levels after pivampicillin were consistenly lower than those recorded in the remaining 7 children beyound the age of 1 year. The mechanism and therapeutic implications of this finding require further study.

Comparative effect of food on absorption of ampicillin and pivampicillin.

The effect of food on the absorption of simultaneously ingested ampicillin or pivampicillin was compared in a crossover study in eight healthy volunteers. The absorption of both ampicillin and pivampicillin was delayed by simultaneous food intake as judged by serum concentration and urinary excretion of ampicillin. The total absorption of ampicillin, but not that of pivampicillin was decreased by simultaneous food intake as indicated by the are under the serum ampicillin concentration-time curves and by 24 hours urinary excretion of ampicillin. The excretion of ampicillin into urine was about 30% of the dose when ampicillin was ingested with water into an empty stomach and about 20% when ingested with food. The respective excretion of ampicillin following the ingestion of pivampicillin was about 60% of the dose taken either with or without food.

[Studies on the pharmacokinetic equivalence of pivampicillin base and hydrochloride in capsules and tablets (author's transl)]. / Untersuchungen zur pharmakokinetischen Aquivalenz von Pivampicillinbase und -hydrochlorid in Kapseln und Tabletten

Absorption and urinary excretion of pivampicillin as hydrochloride and as base were studied following administration of four different formulations to 12 healthy volunteers in a cross-over study. A fluorimetric assay of ampicillin was adapted to be used with an Auto Analyzer system. The plasma concentrations observed are comparable to those reported in the literature. The amount of drug absorbed is the same for all four medications whereas absorption is more rapid from tablets than from capsules. Base and hydrochloride of pivampicillin are equivalent with respect to pharmacokinetic behaviour. So, the formulation itself seems to be more important for biological equivalence than the ionisation of the drug used in the formulation.