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Background and Aims: Ampicillin is 1 of the most commonly used antibiotics for treatment of early onset sepsis, but its pharmacokinetics (PK) is poorly characterized. We aimed to define the dose of ampicillin for late preterm and term neonates by evaluating its PK in serum, cerebrospinal (CSF), and epithelial lining fluid., Methods: A prospective study included neonates receiving ampicillin for suspected or proven early onset sepsis and pneumonia. PK samples were collected at steady state, at predose and 5 minutes, 1 hour, 3 hours, 8 hours, and 12 hours after ampicillin 3-minute infusion. Ampicillin concentrations were measured by ultra-high-performance liquid chromatography. Noncompartmental anaysis (NCA) and population pharmacokinetic (pop-PK) modeling were performed and probability of therapeutic target attainment was simulated., Results: In 14 neonates (GA of 32-42 wks; mean BW 2873 g), PK parameters (mean ± SD) in NCA were the following: half-life 7.21 ± 7.97 hours; volume of distribution (Vd) 1.07 ± 0.51 L; clearance (CL) 0.20 ± 0.13 L/h; 24-hour area under the concentration-time curve 348.92 ± 114.86 mg*h/L. In pop-PK analysis, a 2-compartmental model described the data most adequately with the final parameter estimates of CL 15.15 (CV 40.47%) L/h/70kg; central Vd 24.87 (CV 37.91%) L/70kg; intercompartmental CL 0.39 (CV 868.56) L/h and peripheral Vd 1.039 (CV 69.32%) L. Peutic target attainment simulations demonstrated that a dosage of 50 mg/kg q 12 hours attained 100% fT > MIC 0.25 mg/L, group B streptococcal breakpoint., Conclusions: We recommend ampicillin dosage 50 mg/kg q 12 hours for neonates with gestational age ≥32 weeks during the first week of life., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Purpose: The aim of this study was to compare the in vitro activity of ampicillin and moxifloxacin against six isolates selected from 154 invasive clinical isolates of Listeria monocytogenes and evaluate their intra- and extracellular activities with achievable central nervous system concentrations obtained using Monte Carlo simulations with conventional and unconventional dosages., Methodology: The MICs and minimal bactericidal concentrations (MBCs) of ampicillin and moxifloxacin were determined by using the broth microdilution method. The intra- and extracellular activities were compared using time-kill curves and inhibition of intracellular growth assays., Results: The MICs50/90 of ampicillin were 0.125/0.5 mg l-1 and the MBC50/90 was ≥16 mg l-1, while the moxifloxacin MICs50/90 were 0.25/0.5 mg l-1 and the MBC50/90 was 0.5 mg l-1. Ampicillin did not show any extracellular bactericidal activity at 24 h, although bactericidal activity was detected at 48 h. For moxifloxacin, the bactericidal effect was evident after 6 h of incubation. Both antibiotics achieved significant reductions in intracellular inoculum after 1-24 h of incubation; however, moxifloxacin becomes bactericidal more rapidly, producing a much greater reduction in the inoculum in the first hour than ampicillin. There were no differences among the MIC and MBC values of moxifloxacin and ampicillin among the strains belonging to different serotypes and/or epidemic clones. This fact was also found in the intra- and extracellular studies., Conclusion: The results of this study demonstrated the faster bactericidal activity of moxifloxacin at achievable central nervous system concentrations against intra- and extracellular forms of L. monocytogenes in comparison with ampicillin.

Chronic ethanol consumption is known to downregulate expression of the major glutamate transporter 1 (GLT-1), which increases extracellular glutamate concentrations in subregions of the mesocorticolimbic reward pathway. While β-lactam antibiotics were initially identified as potent upregulators of GLT-1 expression, only ceftriaxone has been extensively studied in various drug addiction models. Therefore, in this study, adult male alcohol-preferring (P) rats exposed chronically to ethanol were treated with other β-lactam antibiotics, ampicillin, cefazolin or cefoperazone (100mg/kg) once daily for five consecutive days to assess their effects on ethanol consumption. The results demonstrated that each compound significantly reduced ethanol intake compared to the saline-treated control group. Importantly, each compound significantly upregulated both GLT-1 and pAKT expressions in the nucleus accumbens and prefrontal cortex compared to saline-treated control group. In addition, only cefoperazone significantly inhibited hepatic aldehyde dehydrogenase-2 enzyme activity. Moreover, these β-lactams exerted only a transient effect on sucrose drinking, suggesting specificity for chronically inhibiting ethanol reward in adult male P rats. Cerebrospinal fluid concentrations of ampicillin, cefazolin or cefoperazone have been confirmed using high-performance liquid chromatography. These findings demonstrate that multiple β-lactam antibiotics demonstrate efficacy in reducing alcohol consumption and appear to be potential therapeutic compounds for treating alcohol abuse and/or dependence. In addition, these results suggest that pAKT may be an important player in this effect, possibly through increased transcription of GLT-1., (Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.)

The fluoroquinolone trovafloxacin was bactericidal (0.47 +/- 0.23 delta log10 CFU/ml x h after 10 mg/kg of body weight and 0.78 +/- 0.15 delta log10 CFU/ml x h after 30 mg/kg) in the treatment of experimental meningitis caused by a highly penicillin-resistant (MIC and minimum bactericidal concentration = 4 and 4 microg/ml) strain of Streptococcus pneumoniae. Combinations with ampicillin and rifampin were indifferent compared to single drugs.

We evaluated the pharmacokinetics and therapeutic efficacy of ampicillin combined with sulbactam in a rabbit model of meningitis due to a beta-lactamase-producing strain of Escherichia coli K-1. Ceftriaxone was used as a comparison drug. The MIC and MBC were 32 and greater than 64 micrograms/ml (ampicillin), greater than 256 and greater than 256 micrograms/ml (sulbactam), 2.0 and 4.0 micrograms/ml (ampicillin-sulbactam [2:1 ratio, ampicillin concentration]) and 0.125 and 0.25 micrograms/ml (ceftriaxone). All antibiotics were given by intravenous bolus injection in a number of dosing regimens. Ampicillin and sulbactam achieved high concentrations in cerebrospinal fluid (CSF) with higher dose regimens, but only moderate bactericidal activity compared with that of ceftriaxone was obtained. CSF bacterial titers were reduced by 0.6 +/- 0.3 log10 CFU/ml/h with the highest ampicillin-sulbactam dose used (500 and 500 mg/kg of body weight, two doses). This was similar to the bactericidal activity achieved by low-dose ceftriaxone (10 mg/kg), while a higher ceftriaxone dose (100 mg/kg) produced a significant increase in bactericidal activity (1.1 +/- 0.4 log10 CFU/ml/h). It appears that ampicillin-sulbactam, despite favorable CSF pharmacokinetics in animals with meningitis, may be of limited value in the treatment of difficult-to-treat beta-lactamase-producing bacteria, against which the combination shows only moderate in vitro activity.

The susceptibilities of 171 bacteria which caused meningitis in 200 children were tested for their susceptibility as minimal inhibitory concentrations (MICs) for the antibiotics used in therapy. These antibiotics were chloramphenicol, ampicillin, cefotaxime and ceftriaxone. The MICs were compared to the minimal concentrations of the drugs seen in the cerebrospinal fluid (CSF) samples. The minimal bacteriostatic capacity (lowest concentration in CSF/MIC) of both cephalosporins was superior to that of chloramphenicol and ampicillin. The correlation of the finding with the speed of liquor sterilization in the treatment groups is discussed.

Infant rats with bacteremia and meningitis induced by ampicillin-resistant Haemophilus influenzae type b were treated with ampicillin and nafcillin, alone or in combination. Neither ampicillin alone (in 19 animals) nor nafcillin alone (in 20 animals) sterilized the blood or cerebrospinal fluid of any treated infant rat. When the combination of ampicillin and nafcillin was used, blood cultures were negative in 18 of 19 infant rats, and cerebrospinal fluid cultures were sterile in 15 of 19 when cultured 30 h after initiation of treatment. In vitro results demonstrated definite synergism between ampicillin and nafcillin against ampicillin-resistant H. influenzae type b. The study suggests that such synergism also exists in vivo.

Unlabelled: In order to avoid other antibiotics which interfere with plasma and CSF level determination of a given antibiotic the authors use a chemical method of established specificity. 15 patients presenting with purulent meningitis were given a standard daily dose of metampicillin and divided into 3 groups of 5. On days 2, 4 and 6 after onset of disease plasma and CSF specimens were taken at respectively 1, 2 or 4 hours following metampicillin I.V. injection according to patient group. All patients were cured between days 7 and 21 of therapy. Tolerance was good., Results: --there was no correlation between dose injected and plasma level of drug,--CSF distribution of metampicillin was good and stayed identical throughout the disease period,--peak CSF drug level was delayed as compared to plasma level, occurring more than 4 hours after I.V. injection of metampicillin.

The in vitro activities of mecillinam, a new beta-amidinopenicillin, and ampicillin, alone and in combination, against an Escherichia coli strain and a Klebsiella pneumoniae strain were compared, and these results were correlated with their respective activities in vivo in experimental meningitis. The mecillinam-ampicillin combination was synergistic in vitro against both strains when tested by a modified checkerboard technique (bacteriostatic synergy). However when quantitative bactericidal synergy studies were made, the relative bactericidal rate of the combination was more rapid than that of either drug alone ("bactericidal synergy") against the Escherichia coli isolate only. In a rabbit model of Enterobacteriaceae meningitis, in vivo bactericidal activity correlated with results obtained in vitro. Both drugs were administered by continuous intravenous infusion for 8 h. Serum and cerebrospinal fluid antibiotic levels were similar to those achieved in humans. Cerebrospinal fluid bacterial concentrations (colony-forming units [CFU] per milliliter) were quantitatively titrated at 2-h intervals. Both drugs, alone or the combination, were ineffective against the K. pneumoniae strain in vivo (change in titer <1 log in 8 h). In contrast, the combination produced a markedly enhanced bactericidal effect against the E. coli strain (mean +/- standard deviation, decrease of log(10) CFU per milliliter of 3.65 +/- 1.02) compared with those of ampicillin alone (decrease of log(10) CFU per milliter of 0.07 +/- 0.8) and mecillinam alone (decrease of log(10) CFU per milliliter of 1.6 +/- 0.05) (P < 0.001). When bactericidal synergism can be demonstrated for mecillinam-ampicillin in vitro in a case of gram-negative-bacillary meningitis this combination may be useful in the therapy of the illness.

Single, intravenously administered doses of cefoxitin and cefamandole did not penetrate into cerebrospinal fluid of normal humans. Multiple-dose administration with or without probenecid facilitated penetration of both antibiotics into the cerebrospinal fluid. Preliminary data showed that cefoxitin penetrated into cerebrospinal fluid of patients with inflamed meninges even when administered in a single dose without probenecid. However, the concentrations of cefoxitin in the cerebrospinal fluid of the individuals studied were not within the therapeutic range.

Cerebrospinal fluid (CSF) sterilization after greater than 24 h of intravenous antibiotic therapy (delayed CSF sterilization) was noted in two infants treated with ceftizoxime and ceftazidime for bacterial meningitis. A case-control study was conducted of children between 6 w and 6 y of age treated between 1975 and 1985 at one institution for bacterial meningitis to determine risk factors for delayed CSF sterilization. Hemophilus influenzae type b was isolated from all children (n = 5) with delayed CSF sterilization, compared with only 78% of all children in the study (n = 83). In children with H. influenzae type b disease, children less than 6 mo of age were at higher risk than older children for delayed CSF sterilization (odds ratio = 7.5, 95% confidence limits = 1.4, 40.0). Factors not associated with delayed CSF sterilization included time of follow-up lumbar puncture, CSF total or differential white blood cell count, and CSF protein and glucose concentrations. Despite the in vitro antimicrobial susceptibility of H. influenzae type b to ceftizoxime and ceftazidime, delayed CSF sterilization may occur in infants receiving these antibiotics for bacterial meningitis.

The relevance of a postantibiotic effect in the treatment of pneumococcal meningitis was evaluated in a rabbit model. After administration of a single intravenous bolus of ampicillin at various dosages, such an effect was observed in all animals. The duration of this effect in vivo (2.5-18 hr) was consistently longer than that in vitro (1-4.3 hr); however, in rabbits the postantibiotic effect was eliminated by the administration of intravenous plus intracisternal beta-lactamase. In an assessment of the potential therapeutic benefit of the postantibiotic effect, the efficacy to two regimens of treatment with different intervals between doses was compared. One group of animals received ampicillin every 4 hr and another every 12 hr. With sufficiently high doses, drug concentrations in cerebrospinal fluid exceeded the minimal bactericidal concentration for most of the 4-hr interval but for only about one-third of the 12-hr interval. The rate of cure was similar for the two regimens and approximated 100% when peak drug concentrations in cerebrospinal fluid exceeded the minimal bactericidal concentration by at least 10-fold.

The activities of cefamandole, cephalothin, ampicillin, and chloramphenicol were compared in fulminant and temperate Escherichia coli meningitis in rabbits. Intensive dosing schedules were employed to achieve maximal therapeutic benefits with short-term treatment. In an 8-h schedule chloramphenicol was significantly more effective in sterilizing the cerebrospinal fluid and curing both fulminant and temperate infections than cefamandole or ampicillin. Cephalothin was without effect in fulminant meningitis. Cefamandole and ampicillin were equivalent in activity in this and longer (12- and 24-hr) treatment schedules. The therapeutic benefits of chloramphenicol were purchased via use of doses above those generally regarded as safe for human use. The mean serum, cerebrospinal fluid, and brain concentrations of chloramphenicol, cefamandole, and ampicillin were significantly greater in rabbits with fulminant meningitis than in those with temperate meningitis. The difference was of such magnitude as to support the need to monitor drug concentrations.

We examined the influence of several pharmacokinetic parameters on cure rates in rabbits with experimental pneumococcal meningitis. When the duration of treatment was kept constant, cure rates improved as the individual dose of ampicillin was increased. On the other hand, when four doses of ampicillin at 60 mg/kg of body weight, producing peak concentrations in cerebrospinal fluid (CSF) of approximately 40 times the MBC, were administered at intervals of 24 instead of 4 h and the duration of therapy was thus prolonged from 12 to 72 h, cure rates also increased (85 versus 25%; P less than 0.01). These high cure rates were achieved even though bacterial titers in CSF 24 h after the first dose had reached levels similar to those present at the beginning of therapy. Cure in these animals was explained by the fact that the second ampicillin dose reduced bacterial titers in CSF significantly more than did the first dose (5.2 versus 2.5 log10 CFU/ml; P less than 0.02). The clinical relevance of these observations remains to be determined.

The penetration of cefamandole and ampicillin into the cerebrospinal fluid of rabbits with and without pneumococcal meningitis was evaluated. In normal animals, a mean maximum concentration of 0.22 +/- 0.13 microgram of cefamandole per ml was measured in the spinal fluid after a dose of 150 mg/kg given intramuscularly; with 25 and 50 mg/kg doses, no antibiotic was detected in the cerebrospinal fluid. With ampicillin, in intramuscular doses of 200 and 300 mg/kg, the mean maximum concentrations encountered in the cerebrospinal fluid were 1.59 +/- 0.4 and 1.47 +/- 0.44 microgram/ml, respectively. Penetration of cefamandole, and to a lesser extent ampicillin, was increased after 24 h of experimental meningitis. With cefamandole, the concentration of drug in the cerebrospinal fluid exceeded the usual inhibitory concentration for Haemophilus influenzae only with the 150 mg/kg dose. After 48 h of meningitis, there was a trend toward higher levels of antibiotic in the cerebrospinal fluid, but the difference between animals infected 24 versus 48 h was not statistically significant. In animals with meningitis, serum concentrations after 150 mg of cefamandole per kg and both ampicillin doses studied were 32 to 38% lower than the serum levels achieved in normal rabbits after identical doses of antibiotic.

Pharmacokinetic differences between ampicillin and carbenicillin in the cerebrospinal fluid (CSF) were evaluated in experimental staphylococcal meningitis in rabbits after a single intravenous administration of 100 mg/kg dose of each drug. Half-lives (T 1/2) in CSF and CSF/serum ratios of T 1/2 were 52 minutes and 2.1 for ampicillin and 23 minutes and 1.3 for carbenicillin, respectively. These findings indicate that ampicillin is eliminated from CSF more slowly than carbenicillin. Penetration rates were calculated from CSF/serum ratios of area under the curve (AUC) and were 16.8% for ampicillin and 11.6% for carbenicillin, although the maximum concentration (Cmax) of carbenicillin in CSF was twice as high as that of ampicillin. Thus the penetration rate appeared to be influenced more by T 1/2 in CSF than by Cmax. Cmax in CSF was obtained at 15 minutes for carbenicillin and 30 minutes for ampicillin. As to carbenicillin there were considerable individual variations in CSF levels. The above observations suggest that T 1/2 and AUC in CSF are important parameters when evaluating the usefulness of an antibiotic in the treatment of bacterial meningitis.

Meningitis was induced in white rabbits with a non beta-lactamase producing strain of Staphylococcus aureus. There was no significant difference in the CSF level of ceftazidime after simultaneous administration of ceftazidime with ampicillin or after ceftazidime alone. In contrast the percentage CSF penetration of ampicillin decreased from 8.81% after administration of ampicillin alone to 2.77% after the simultaneous administration of ampicillin with ceftazidime. The ratio of AUC in CSF and serum was 19.4% after ampicillin alone and 7.71% after simultaneous administration with ceftazidime. When ceftriaxone was combined with ampicillin there was no effect on the CSF penetration of either drug. Cephalosporins have unpredictable effects on the CSF concentration of ampicillin, probably due to variable effects on the penetration of ampicillin from blood to CSF.

The concentration of antibiotic in cerebrospinal fluid was measured during treatment of seven children with infected ventricular shunts. Antibiotics were administered via the ventricular shunt or through an external ventricular drain. 53 CSF samples were obtained 7-19 h after antibiotic administration. Wide variation in cerebrospinal fluid antibiotic concentration occurred from patient to patient following either route of administration. For optimal management of shunt infections, we recommend periodic assessment of antibiotic concentration or activity in ventricular fluid and determination of the minimum inhibitory concentration of antibiotic required for each pathogen.

The influence of methylprednisolone on the passage of ampicillin and gentamicin into and activity within cerebrospinal fluid was examined in two models of experimental meningitis. Steroid pretreatment reduced the concentrations of these drugs in purulent cerebrospinal fluid of rabbits with experimental pneumococcal and Escherichia coli meningitis (P less than 0.05). However, the resultant mean concentrations of these antibiotics in cerebrospinal fluid still exceeded the minimal bactericidal concentrations of the infecting organisms. The rate of bactericidal effect in vivo was unaffected by steroid therapy in each model. Methylprednisolone did not have deleterious effects on the course of treated experimental meningitis under these short-term (24-h) experiments.

Eighty-one patients ages one month to 14 years with meningitis were randomized to receive either sulbactam (50 mg/kg per day) and ampicillin (400 mg/kg per day; 41 patients) or chloramphenicol and ampicillin (40 patients). The groups were comparable in terms of sex and degree of illness; however, more patients treated with chloramphenicol/ampicillin than patients treated with sulbactam/ampicillin were younger than 12 months of age (78% vs. 56%). Pathogens were isolated from the cerebrospinal fluid (CSF) of 65 (80%) of the 81 patients. In the sulbactam/ampicillin group, there were 18 Haemophilus influenzae isolates (one resistant to ampicillin), five Streptococcus pneumoniae, five Neisseria meningitidis, one Klebsiella pneumoniae, one Pseudomonas aeruginosa, and one Listeria. In the chloramphenicol/ampicillin group, there were 19 H. influenzae isolates, 10 S. pneumoniae, three N. meningitidis, one Haemophilus parainfluenzae, and one Citrobacter. Of 63 patients with assessable CSF pathogens, one (3%) of 29 treated with sulbactam/ampicillin died (S. pneumoniae) and six (18%) of 34 treated with chloramphenicol/ampicillin died (two, H. influenzae; three, S. pneumoniae; and one, Citrobacter). Twelve percent in the sulbactam/ampicillin group and 18% in the chloramphenicol/ampicillin group had neurologic sequelae. No clinically significant reactions or toxicities were noted. Sulbactam/ampicillin was as effective as chloramphenicol/ampicillin in the treatment of meningitis.

Pharmacokinetic differences between a bolus and a 60 minutes continuous intravenous administration of 100 mg/kg dose of ampicillin in the cerebrospinal fluid (CSF) were evaluated in the rabbits with experimental staphylococcal meningitis. The maximum concentrations in CSF were 19.3 micrograms/ml for bolus injection and 7.24 micrograms/ml for 60 minutes continuous infusion. Half-lives (T1/2) in CSF and CSF/serum ratios of T1/2 were 29.9 minutes and 1.3 minutes for bolus injection and 48.1 minutes and 1.9 minutes for 60 minutes continuous infusion, respectively. These findings indicate that extremely high concentrations of short duration in serum are required to elevate the concentrations in CSF and the maintenance of certain concentrations in serum are required to keep concentrations above the therapeutic concentrations in CSF. The mean penetration rate derived from the CSF/serum ratios of AUC were 11.1% for bolus injection and 5.5% for 60 minutes continuous infusion. Thus bolus injection is considered to be superior to 60 minutes continuous infusion pharmacokinetically. Bacterial meningitis is one of the diseases in which therapeutic concentrations of antibiotics are difficult to attain at the the site of infections. Therefore, when an intravenous ampicillin is going to be used in the treatment of bacterial meningitis, bolus injection is preferred to 60 minutes continuous infusion.

Two patients with purulent meningitis, of which causative organism was presumed to be E. coli, were treated with intravenous administration of cefmetazole, 300 approximately 400 mg/kg/day in 4 approximately 6 divided doses, and the following conclusions were obtained. 1) Clinical response was favorable and a complete cure was obtained without sequelae in both patients. There were no adverse reactions noted except for a mild and transient eosinophilia (12%) in one case. 2) Of two strains of E. coli recovered from CSF, one was sensitive to ampicillin, cefazolin and cefmetazole, among which cefmetazole had the highest bacterial activity. Although another strain was sensitive to cefmetazole, it showed resistance to cefazolin (greater than 12.5 microgram/ml) and to ampicillin (greater than 100 microgram/ml). 3) Concentrations of cefmetazole in CSF following 1 approximately 2 hours of its intravenous administration were either equal to or higher than those of ampicillin, which was given to the same patient for a short period of time. The concentrations in CSF were higher than 3.1 microgram/ml on each occasion except for in some specimens during the convalescent phase and exceeded well the MIC of the causative organism. 4) Based on the above results, cefmetazole is considered to be a potent antibiotic in the treatment of E. coli meningitis. Although further studies are needed as to the dosage, an intravenous administration at 4-hour interval appears to be warranted based on the studies that the half-life of the drug is short in CSF in animal experiments.

Forty-three infants and children with bacterial meningitis were treated intravenously with 200 mg of amoxicillin sodium per kg per day for 10 days. (Patients were initially treated with ampicillin and chloramphenicol until the bacterial etiology was defined.) Patients were randomly treated with amoxicillin only or with amoxicillin and four doses of probenecid (10 mg/kg per dose) orally every 6 h for 24 h before the lumbar puncture at day 10. Serum and cerebrospinal fluid (CSF) were obtained on days 1, 5, and 10 of therapy for antibiotic assay. The mean peak serum concentration of amoxicillin of 49.2 micrograms/ml was increased to 61.4 micrograms/ml in patients who received probenecid. The half-life in serum (1.5 h) and area under the curve with probenecid (112.5 micrograms/ml-h) were increased compared with those of amoxicillin alone (1.3 h and 82.2 micrograms/ml-h). The mean peak CSF concentrations on days 1 and 5 were similar, but day 1 concentrations remained between 2.0 micrograms/ml and 5.0 micrograms/ml throughout the 4 h after a dose, whereas the day 5 values decreased at the same decay rate as that in serum. All CSF concentrations were lower on day 10, but patients receiving probenecid had peak values occurring at 1 hr rather than at 0.5 h, and levels were significantly greater at 1 and 2 h after a dose. There were no deaths and patients responded well to treatment.

The distribution of ampicillin between blood and cerebrospinal fluid was compared in patients with serous meningitis to that in patients without inflammation of the meningeal membranes. Ampicillin was applied as a continuous intravenous infusion. Samples of blood and cerebrospinal fluid were taken after 1,2,4 or 12 h for the determination of the ampicillin concentrations. In both groups of patients the ratio of concentration in cerebrospinal fluid to concentration in plasma rose between the first and second hour after administration and reached a steady-state value thereafter. This steady-state ratio was 0.025 in patients without meningitis and 0.061 in patients with meningitis. These results are discussed in the context of a pharmacokinetic model which describes the distribution of drugs between blood and cerebrospinal fluid.

A study was done on cefodizime (THR-221, CDZM) in combination with ampicillin (ABPC) for its transferability to cerebrospinal fluid (CSF) of rabbits with experimental meningitis caused by Staphylococcus aureus. Blood and CSF were collected at 15, 30, 45, 60, 90, 120 and 180 minutes after intravenous administration of CDZM at 100 mg/kg to 6 rabbits, ABPC at 100 mg/kg to 4 rabbits and simultaneous administration of both drugs at 100 mg/kg each to 5 rabbits. Drug concentrations were assayed with an high performance liquid chromatography method, and pharmacokinetic parameters were calculated. The comparison revealed no significant difference in concentrations achieved among different groups. Therefore, the mutual transferability of these drugs to CSF was not considered to interact adversely due to the simultaneous administration of both drugs. Accordingly, CDZM may be a candidate of chemotherapeutics in the therapy of purulent meningitis, and it is worthy of further investigations.

1. With a constant plasma concentration of Ampicillin the ratio of concentration in the cerebrospinal fluid to concentration in the plasma reaches a constant value after 2 hrs in patients with and without serous meningitis. 2. Patients without serous meningitis have a value of 0.025, patients with serous meningitis a value of 0.061. 3. From this it can be calculated that Ampicillin passes two and a half times faster through inflamed meningeal membranes than unaffected membranes.

The relative effectiveness of bolus vs. constant intravenous administration of equivalent doses of penicillin G in killing bacteria in vivo was studied in a rabbit model of meningitis due to Streptococcus pneumoniae. Samples of cerebrospinal fluid (CSF) and serum were obtained from 30 rabbits at intervals of less than or equal to 8 hr after treatment for determination of antibiotic concentrations and titers of viable bacteria in the CSF. When penicillin G was given by continuous infusion (10(5) units/hr after an initial 10(5)-unit loading dose), concentrations of drug in serum and CSF reached a steady state in 1 hr. With intermittent bolus administration of 4 x 10(5) units every 4 hr, higher peak and lower trough concentrations were achieved, and these concentrations paralleled those in the CSF. Although an initial acceleration in bactericidal rate was observed with the bolus infusion between the first and second hour of therapy, after the second hour the rate of bacterial killing was identical for the two methods of administration. The duration of therapy required for sterilization of the CSF was dependent only on the bacterial count before treatment and not on the mode of drug administration. The effect of single bolus intravenous administration of ampicillin was examined in experimental pneumococcal meningitis. Ampicillin was given at various dosages (3.25-62.5 mg/kg), and frequent samples of CSF were obtained for determination of concentrations of pneumococci and ampicillin. A long postantibiotic effect was observed in the CSF of all animals, and this effect consistently was longer than that observed in vitro.

The penetration of antibiotics into the cerebrospinal fluid (CSF) is governed by several factors, including lipid solubility, degree of ionization, pH gradient, serum protein binding, molecular weight and structure and, above all, degree of meningeal inflammation. The distribution within, and elimination from the subarachnoid spaces depend upon the physiology of the CSF and the route of administration of the drug. CSF penetration studies carried out in patients or volunteers with various groups of antibiotics and antibacterial agents have shown that, except for chloramphenicol and co-trimixazole, passage through the blood-brain barrier is generally poor. However, when the meninges are inflamed therapeutically active concentrations of penicillins and of some cephalosporins can be measured in the CSF.

The pharmacokinetics of cefotaxime and ampicillin in the cerebrospinal fluid (CSF) were studied by a HPLC method after administering each of the antibiotics singly or as a mixture to rabbits with experimental meningitis caused by Staphylococcus aureus. The half-lives of cefotaxime and desacetyl-cefotaxime in the serum and of ampicillin in the CSF were found to be significantly shorter in the mixture group than in the respective single administration groups. No other statistically significant differences were observed between the mixture and single administration groups with respect to the maximum concentrations (Cmax) of the antibiotics in the serum and the CSF, to the relative percentage of the Cmax of each antibiotic in the CSF to the Cmax in the serum, and to the relative percentage of the AUC of each antibiotic in the CSF to that in the serum. These results differ from earlier findings that the concentration of ampicillin in the CSF of rabbits was significantly lower in animals concomitantly dosed with latamoxef (moxalactam) and ampicillin than in a group dosed only with ampicillin.

Infusions of 50 mg of sulbactam per kg per day and 400 mg of ampicillin per kg per day in divided doses to infants and children with bacterial meningitis produced levels in cerebrospinal fluid approximately one-third those in serum. Concentrations in cerebrospinal fluid of 5.5 micrograms of sulbactam per ml and 16.0 micrograms of ampicillin per ml declined within a few days of therapy to 1.9 microgram of sulbactam per ml and 5.2 micrograms of ampicillin per ml.

To evaluate cotrimoxazole in the treatment of bacterial meningitis, we compared its action with that of ampicillin and chloramphenicol in experimental Haemophilus influenzae type b meningitis. Both trimethoprim and sulfamethoxazole penetrated well into the cerebrospinal fluid of infected rabbits, reaching 40 and 26%, respectively, of their simultaneous serum levels. Levels measured 30 and 60 min after intravenous injection exceeded the minimum inhibitory concentration of this combination for H. influenzae by 10- to 100-fold. The mean ratio of trimethoprim to sulfamethoxazole in cerebrospinal fluid was 1:22. Cotrimoxazole was as effective as ampicillin in therapy of beta-lactamase-negative H. influenzae meningitis and as effective as chloramphenicol for a beta-lactamase positive strain. These findings corroborate favorable preliminary clinical experience reported by others and indicate that cotrimoxazole deserves further study in the therapy of bacterial meningitis.

For the specific and unspecific treatment of purulent meningitis, penicillin, ampicillin and chloramphenicol are usually sufficient. Only resistant pathogens (Klebsiella, Pseudomonas among others) and meningitis in infants require other treatment. Cephalosporins and aminoglycosides only come into consideration for the treatment of very rare exceptional cases. The still relatively poor prognosis of purulent meningitis is largely independent of the efficacy of the treatment. Delay in beginning therapy, lack of intensive care, primary diseases and complications are principally responsible for this. Medicamentous prophylaxis is only possible for meningococcal meningitis. The distribution of antibiotics in the CSF is irregular. Also the antibacterial activity in the CSF is different from culture media.

Thirty-five neonates with suspected septicaemia were randomized to treatment with tobramycin or ceftazidime, both in combination with ampicillin. Concentrations of antibiotics in the CSF were measured 1 h after the third, fourth or fifth injection. In 13 of 17 neonates tobramycin CSF concentrations were below 0.5 mg/l. Ceftazidime CSF concentrations ranged from 2.5 to 17 mg/l, which should be sufficient for treatment of infections with group B streptococci and most aerobic gram-negative bacilli but not all strains of Staphylococcus aureus. Ampicillin CSF concentrations ranged from 1 to 80 mg/l, which should be sufficient for treatment of meningitis caused by enterococci and Listeria monocytogenes, the most important neonatal pathogens not covered by ceftazidime.

Sixty-two children with Haemophilus meningitis were treated with ampicillin sodium, 200 mg/kg/day for ten days. Thirty-one received the drug intravenously (IV) for ten days; the other 31 patients received ampicillin IV for five days (except for one test dose given intramuscularly [IM] on day 2) followed by IM administration of ampicillin the last five days. Ampicillin concentrations in cerebrospinal fluid (SCF) were higher one hour after IV administration, but at two and four hours, concentrations were greater after IM doses. Responses to therapy and rates of complications were similar in the two groups. Fourteen patients had positive CSF cultures on day 2. Ten of these were isolated only on Levinthal medium and would have been overlooked with routine culture methods. All organisms were ampicillin-susceptible and all CSF cultures were negative by 48 hours. More patients with delayed sterilization had neurologic sequelae (78%) than patients with prompt CSF sterilization (13%). The schedule of five days of IV treatment followed by five days of IM therapy was pharmacologically and clinically as effective as ten days of IV therapy and has practical advantages.

Concentrations of sulbactam in the CSF of 18 patients with bacterial meningitis who were undergoing treatment with intravenous (iv) ampicillin were determined. Six patients received single doses of sulbactam (1 g) and 12 patients received multiple doses (four times daily) by the iv route at various intervals before lumbar punctures were performed to monitor their condition. Concentrations of sulbactam up to 12 micrograms/ml were detected in the CSF between 1 and 4 hr after dosing, the higher levels being present in the CSF of patients with the most severe meningeal inflammation. There were no significant differences in the concentrations achieved after single or multiple doses of sulbactam, and the concentrations were generally similar to the concurrent concentrations of ampicillin. It is concluded that these results as well as the antibacterial properties of sulbactam plus ampicillin support the evaluation of this combination as an alternative in the treatment of bacterial meningitis.

Aztreonam (AZT) and ampicillin (ABPC) were independently administered to 6 and 7 rabbits respectively, with S. aureus meningitis. Additionally, AZT and ABPC were concomitantly given to 6 rabbits with S. aureus meningitis. Concentrations of AZT and ABPC in cerebrospinal fluid (CSF) and serum were determined by HPLC method, and the results in concomitant treatment were compared with those for single treatment of each agent. Results were as follows: Maximum serum concentrations of AZT in concomitant treatment of AZT and ABPC were higher than those in single treatment of AZT. However, there was no significant difference between the 2 treatment groups with regard to maximum CSF concentration, percentage of AUC of CSF to serum, and T1/2 of the CSF and serum concentrations of AZT. ABPC in the concomitant treatment did not influence the CSF concentration of AZT. There was no significant difference in serum concentration of ABPC between concomitant treatment and the single one. However, the values of maximum CSF concentration, percentage of maximum CSF to serum concentration and percentage of AUC of CSF to serum in the concomitant treatment were lower than those in the single treatment of ABPC. With regard to T1/2 of CSF concentration of ABPC, there was no remarkable difference between the 2 treatment groups. The above results suggest that the distribution of ABPC into CSF is suppressed in the concomitant treatment of AZT and ABPC. AZT has no antimicrobial activity against Gram-positive bacteria. The CSF concentration of ABPC is suppressed in the concomitant treatment. Those facts suggest that AZT should be administered for meningitis cases after the identification of causative pathogens.

Amoxicillin and ampicillin levels were comparatively studied in blood and CSF of children with purulent meningitis. Thirty one children aged 2 months to 11 years were treated by one of two beta lactams by monotherapy in a daily dose of 200 mg/kg (Group 1: amoxicillin, n = 17; group 2: ampicillin, n = 14). Samples were collected on day 2 one hour after administration of 50 mg/kg IV of the chosen antibiotic. The mean levels observed in serum (69.5 and 53.4 micrograms/ml) and in CSF (7.74 and 7.96) were not significantly different. Beyond these levels we studied different biologic parameters in CSF: leucocytes, polymorphonuclears, protein, glucose and lactic acid. Multiple linear correlations were found, for the two groups and for the whole population between the CSF antibiotic level and the 6 other parameters (group 1: R1 = 0.82; group 2: R2 = 0.88; group 1 + 2: R3 = 0.78). The best correlated parameters with antibiotic CSF level are serum antibiotic level and CSF lactic acid. With these two parameters we can also estimate antibiotic level in CSF with good correlations (R1 = 0.78; R2 = 0.72 and R3 = 0.72).

Concentrations of sulbactam (SBT) and ampicillin (ABPC) in the blood and cerebrospinal fluid (CSF) following an intravenous administration of SBT/ABPC at a dose of 150 mg/kg (SBT/ABPC = 1:2) were determined in 12 rabbits with staphylococcal meningitis. Drug concentrations were measured 9 times, 6 times each with intervals of 15 minutes and thereafter with intervals of 30 minutes. The results were compared with those of a group of 9 rabbits given 100 mg/kg of ABPC alone. 1. The maximum concentration of SBT in the CSF and the percentages of both the maximum concentration and the area under the concentration-time curve (AUC) of SBT in CSF vs. those in serum of the SBT/ABPC group were higher than those of ABPC and the half-life of SBT in the CSF was also longer than that of ABPC, all with significant difference. When these parameters for SBT of SBT/ABPC groups were compared with those of ABPC of the ABPC group, not much differences existed between the 2 groups except that the CSF half-life of SBT was much longer than that of ABPC. 2. The percentages of both the maximum concentration and AUC of ABPC in CSF vs. those in serum of the SBT/ABPC group were significantly lower than those of ABPC of the ABPC group. The CSF half-life of ABPC of the former group was longer than that of the latter. 3. The above results suggest that when SBT and ABPC are administered simultaneously, the penetration of ABPC into the CSF is inhibited.

A new methoxymethyl ester of hetacillin is highly lipid-soluble, a property which was expected to enhance its penetration into the central nervous system (CNS). We compared the penetration of the ester and ampicillin into the cerebrospinal fluid (CSF) of normal rabbits and those with experimental Hemophilus influenzae meningitis. In normal rabbits treated by constant intravenous infusion, mean per cent penetration (see article) of the ester was four times as great as that of ampicillin (6.6 +/- 3.7% against 1.6 +/- 1.9%), and the difference in CSF drug levels attained was accentuated when bolus IV infusion was used. Drug concentration in brain tissue was three times as great in a rabbit treated with the ester (0.79 mug/gm against 0.26 mug/gm). In rabbits with meningitis, the ester again achieved higher CSF concentrations. Per cent penetration into CSF in infected rabbits was 23% for the ester and 13% for ampicillin. Bactericidal activity of the drugs was comparable; over 8 hr of treatment both drugs significantly reduced the CSF bacterial titers of infected animals. Our data demonstrated that the ester enters the CSF and CNS in higher concentration than ampicillin, with no loss in bactericidal activity.

Concentrations of ampicillin and the methoxymethyl ester of hetacillin were measured in plasma, prostatic fluid, and spinal fluid of dogs receiving ampicillin or the hetacillin ester by continuous intravenous infusion. The ratios of ampicillin in prostatic fluid relative to plasma levels were higher after dosing with the hetacillin ester. Pharmacokinetic parameter values were consistent with urinary excretion characteristics. Ready diffusion of the ester across biological membranes may facilitate eradication of pathogenic organisms in prostatic and spinal fluids.

A rabbit model of pneumococcal meningitis was used to examine the importance of bactericidal vs. bacteriostatic antimicrobial agents in the therapy of meningitis 112 animals were infected with one of two strains of type III Streptococcus pneumoniae. Both strains were exquisitely sensitive to ampicillin, minimum inhibitory concentration (MIC)/minimum bactericidal concentration (MBC)<0.125 mug/ml. The activity of chloramphenicol against the two strains varied: strain(1)-MIC 2 mug/ml, MBC 16 mug/ml; strain(2)-MIC 1 mug/ml, MBC 2 mug/ml. Animals were treated with either ampicillin or chloramphenicol in dosages that achieved a peak bactericidal effect in cerebrospinal fluid (CSF) for ampicillin against both strains. Two different dosages were used for chloramphenicol. The first dosage achieved a peak CSF concentration of 4.4+/-1.1 mug/ml that produced a bacteriostatic effect against strain(1) and bactericidal effect against strain(2). The second dosage achieved a bactericidal effect against both strains (mean peak CSF concentration 30.0 mug/ml). All animals were treated intramuscularly three times a day for 5 d. CSF was sampled daily and 3 d after discontinuation of therapy for quantitative bacterial cultures. Results demonstrate that only antimicrobial therapy that achieved a bactericidal effect in CSF was associated with cure. Over 90% of animals treated with one of the bactericidal regimens (i.e., animals in which the bacterial counts in CSF dropped >5 log(10) colony-forming units [cfu]/ ml after 48 h) had sterile CSF after 5 d of treatment. On the other hand, the regimen that achieved bacteriostatic concentrations (CSF drug concentrations between the MIC and MBC) produced a drop of 2.4 log(10) cfu/ml by 48 h; however, none of the animals that survived had sterile CSF after 5 d. These studies clearly demonstrate in a strictly controlled manner that maximally effective antimicrobial therapy of experimental pneumococcal meningitis depends on achieving a bactericidal effect in CSF.

The entry of amoxicillin and ampicillin into cerebrospinal fluid (CSF) of humans was studied in the absence of meningeal inflammation. Twelve volunteers received 33 mg of amoxicillin per kg intravenously over 30 min and nine volunteers received 33 mg of ampicillin per kg. The CSF specimens were sampled at 1, 2, and 4 h after the beginning of the infusion. Blood samples were obtained at the end of the infusion and at 45, 60, 90, 120, 180, and 240 min after the beginning of the infusion. Amoxicillin and ampicillin were both detected in the CSF. Ampicillin tended to give higher CSF levels than amoxicillin, although the difference was small. Serum concentrations of ampicillin equaled those of amoxicillin.