Pharmacokinetics of ceftriaxone in neonates and infants with meningitis

Predicting Volume of Distribution in Neonates: Performance of Physiologically Based Pharmacokinetic Modelling

The volume of distribution at steady state (Vss) in neonates is still often estimated through isometric scaling from adult values, disregarding developmental changes beyond body weight. This study aimed to compare the accuracy of two physiologically based pharmacokinetic (PBPK) Vss prediction methods in neonates (Poulin & Theil with Berezhkovskiy correction (P&T+) and Rodgers & Rowland (R&R)) with isometrical scaling. PBPK models were developed for 24 drugs using in-vitro and in-silico data. Simulations were done in Simcyp (V22) using predefined populations. Clinical data from 86 studies in neonates (including preterms) were used for comparison, and accuracy was assessed using (absolute) average fold errors ((A)AFEs). Isometric scaling resulted in underestimated Vss values in neonates (AFE: 0.61), and both PBPK methods reduced the magnitude of underprediction (AFE: 0.82-0.83). The P&T+ method demonstrated superior overall accuracy compared to isometric scaling (AAFE of 1.68 and 1.77, respectively), while the R&R method exhibited lower overall accuracy (AAFE: 2.03). Drug characteristics (LogP and ionization type) and inclusion of preterm neonates did not significantly impact the magnitude of error associated with isometric scaling or PBPK modeling. These results highlight both the limitations and the applicability of PBPK methods for the prediction of Vss in the absence of clinical data.

Validated HPLC method for ceftriaxone from dried blood spots for pharmacokinetic studies and therapeutic drug monitoring in neonatal population

Background: Pharmacokinetic evaluation is essential for the precise dosing of ceftriaxone in neonates. There is a need for developing a sensitive, affordable and convenient analytical method that can estimate ceftriaxone from dried blood spot (DBS) samples of neonates. Method: An HPLC-UV method was developed and validated as per ICH M10 for ceftriaxone from DBS and plasma using an Inertsil-ODS-3V column with gradient elution. DBS samples were extracted with methanol. Clinical validation was performed using neonatal samples. Results: The developed plasma- and DBS-based-HPLC method were linear from 2-700 μg/ml and 2-500 μg/ml, respectively, for ceftriaxone. Bland-Altman analysis indicated a strong interconvertibility between the plasma and DBS assays. Conclusion: Observed concentrations in clinical samples were comparable to the predicted concentrations, proving the clinical validity of the method.

Bilirubin-Displacing Effect of Ceftriaxone in Infants With Unconjugated Hyperbilirubinemia Born at Term

OBJECTIVE

To evaluate the effect of intravenous (IV) ceftriaxone on free bilirubin concentrations in infants with unconjugated hyperbilirubinemia born at term.

STUDY DESIGN

A prospective study was performed with subjects serving as their own controls. Our inclusion criteria were infants born at term <7 days old with sepsis and receiving IV antibiotics for >3 days and resolving hyperbilirubinemia with total serum bilirubin levels between 6 and12 mg/dL by day 4 of life. Free bilirubin concentrations were measured by the peroxidase method using a UB analyzer and a Zone Fluidics device before (baseline) and 15 minutes after (follow-up) IV ceftriaxone administration on postnatal days 4 to 6. Paired measurements of free bilirubin were analyzed using a Student paired t-test or Wilcoxon signed-rank test.

RESULTS

In total, 27 infants were studied. The mean free bilirubin (μg/dL) at follow-up was not different from that at baseline when measured by the UB analyzer (P = .78). The mean free bilirubin was significantly lower at follow-up compared with baseline when measured by the Zone Fluidics device (P = .02). The ratio of a free bilirubin with and without ceftriaxone, an index of displacing effect, was 1.02 (95% CI 0.89-1.14) using the UB analyzer and 0.58 (95% CI 0.30-0.86) using the Zone Fluidics device.

CONCLUSIONS

Ceftriaxone is not associated with a bilirubin-displacing effect in infants with a mild unconjugated hyperbilirubinemia. Home therapy with once-daily intramuscular ceftriaxone may be an alternative option for management of sepsis in asymptomatic infants with a mild unconjugated hyperbilirubinemia born at term.

Treatment options for neonatal infections in the post-cefotaxime era

INTRODUCTION

: Cefotaxime has been used for the management of neonatal infections since the 1990s for suspected meningitis and to mitigate gentamicin-associated renal injury. Its shortage in 2015 and subsequent removal from the U.S. pharmaceutical market forced providers to consider alternatives. Ceftriaxone, a cephalosporin with an identical antibacterial spectrum of activity to cefotaxime, is contraindicated in neonates due to its risk of biliary pseudolithiasis. Ceftazidime was recommended as an alternative by the American Academy of Pediatrics but is inequivalent.

AREAS COVERED

: This article addresses indications for cephalosporin use and considerations when selecting an alternative to cefotaxime. Differences among cefotaxime, ceftriaxone, ceftazidime, and cefepime are discussed and compared to the standard-of-care presumptive regimen, ampicillin and gentamicin. The authors consider the data behind the neonatal contraindication to ceftriaxone and provide recommendations for their application to practice.

EXPERT OPINION

: The data against ceftriaxone use in neonates remain poor, particularly in the context of the cefotaxime shortage and lack of an equivalent alternative. Ceftriaxone could be considered in low-risk neonates without hyperbilirubinemia or exposure to calcium-containing fluids on a case-by-case basis. Ceftazidime monotherapy for presumptive management of neonatal infections is inappropriate; cefepime should be more frequently utilized in neonates who are poor candidates for ceftriaxone.

Effect of P-glycoprotein Inhibition on the Penetration of Ceftriaxone Across the Blood-Brain Barrier

Recent studies indicate that inhibition of the efflux transporter P-glycoprotein (P-gp) at the blood-brain barrier (BBB) may represent a putative strategy to increase the BBB penetration of several antibiotics. Therefore, the present study aimed to investigate the effect of P-gp inhibition on the transport of ceftriaxone (CFX) across the BBB. Blood and brain microdialysis in rats was used to monitor blood and brain unbound CFX concentrations following intravenous administration (50 mg/kg), with or without pretreatment with one of the P-gp inhibitors, cyclosporin A (6.25, 12.5, 25 mg/kg) or verapamil (5, 10, 20 mg/kg). An inhibitory effect was demonstrated by an increase in the ratio of unbound brain to unbound blood concentration (Kp.uu.brain) of CFX. The concentrations of CFX in blood and brain from 0 to 180 min after intravenous administration (CFX, 50 mg/kg) ranged from 3 to 40 μg/ml and 1 to 10 μg/ml, respectively. The Kp.uu.brain of CFX was 24.74 ± 1.34%. Pretreatment with cyclosporin A increased the brain concentration and the Kp.uu.brain of CFX in a dose-dependent manner. However, pretreatment with verapamil increased the brain concentration of CFX but not the Kp.uu.brain. The present data shows that CFX might be a substrate of P-gp efflux transporter at the BBB and P-gp inhibition might enhance the brain concentration of CFX. Future studies involving more selective P-gp inhibitors or knockout mouse models should be conducted to specifically elucidate the impact of P-gp inhibition on penetration of CFX across the BBB.

Evaluation of Ceftriaxone Plus Avibactam in an Intracellular Hollow Fiber Model of Tuberculosis: Implications for the Treatment of Disseminated and Meningeal Tuberculosis in Children

BACKGROUND

Ceftazidime-avibactam is an effective agent for the treatment of tuberculosis (TB) but requires frequent administration because of a short half-life. Due to a longer half-life, ceftriaxone could allow intermittent dosing.

METHODS

First, we identified the MIC of ceftriaxone with 15 mg/L avibactam in 30 clinical Mycobacterium tuberculosis isolates. Next, 2 ceftriaxone exposure-effect studies in the intracellular hollow fiber model of TB (HFS-TB) that mimics disseminated disease in young children, were performed. Ceftriaxone was administered once or twice daily for 28 days to explore percentage of time that the concentration persisted above MIC (%TMIC) ranging from 0 to 100%. In a third HFS-TB experiment, the "double cephalosporin" regimen of ceftazidime-ceftriaxone-avibactam was examined and analyzed using Bliss Independence.

CONCLUSION

The MIC99 of the clinical strains was 32 mg/L, in the presence of 15 mg/L avibactam. Ceftriaxone %TMIC <42 had no microbial effect in the HFS-TB, %TMIC >54% demonstrated a 4.1 log10 colony-forming units per milliliter M. tuberculosis kill, while %TMIC mediating Emax was 68%. The "double cephalosporin" combination was highly synergistic. Monte Carlo experiments of 10,000 subjects identified the optimal ceftriaxone dose as 100 mg/kg twice a day.

CONCLUSION

The combination of ceftriaxone-avibactam at 100 mg/kg could achieve Emax in >90% of children. The ceftriaxone potent activity M. tuberculosis could potentially shorten therapy in children with disseminated TB.

Optimal Dosing of Ceftriaxone in Infants Based on a Developmental Population Pharmacokinetic-Pharmacodynamic Analysis

Ceftriaxone is a third-generation cephalosporin used to treat infants with community-acquired pneumonia. Currently, there is a large variability in the amount of ceftriaxone used for this purpose in this particular age group, and an evidence-based optimal dose is still unavailable. Therefore, we investigated the population pharmacokinetics of ceftriaxone in infants and performed a developmental pharmacokinetic-pharmacodynamic analysis to determine the optimal dose of ceftriaxone for the treatment of infants with community-acquired pneumonia. A prospective, open-label pharmacokinetic study of ceftriaxone was conducted in infants (between 1 month and 2 years of age), adopting an opportunistic sampling strategy to collect blood samples and applying high-performance liquid chromatography to quantify ceftriaxone concentrations. Developmental population pharmacokinetic-pharmacodynamic analysis was conducted using nonlinear mixed effects modeling (NONMEM) software. Sixty-six infants were included, and 169 samples were available for pharmacokinetic analysis. A one-compartment model with first-order elimination matched the data best. Covariate analysis elucidated that age and weight significantly affected ceftriaxone pharmacokinetics. According to the results of a Monte Carlo simulation, with a pharmacokinetic-pharmacodynamic target of a free drug concentration above the MIC during 70% of the dosing interval (70% fT _>MIC), regimens of 20 mg/kg of body weight twice daily for infants under 1 year of age and 30 mg/kg twice daily for those older than 1 year of age were suggested. The population pharmacokinetics of ceftriaxone were established in infants, and evidence-based dosing regimens for community-acquired pneumonia were suggested based on developmental pharmacokinetics-pharmacodynamics.

Duration of empirical therapy in neonatal bacterial meningitis with third generation cephalosporin: a multicenter retrospective study

INTRODUCTION

The duration of treatment is not well established, especially in the negative cerebrospinal fluid (CSF) culture. The aim of this study is to explore the influence of duration of treatment in neonatal bacterial meningitis.

MATERIAL AND METHODS

This is a retrospective analysis of 200 CSF specimens. Two hundred full-term neonates with bacterial meningitis admitted to the clinical status were evaluated using the Glasgow Outcome Scale (GOS) on the day of discharge.

RESULTS

Neonates were identified as having bacterial meningitis based on the results of CSF culture tests of all suspected cases. According to the GOS, neonates were divided into two outcome groups: 77.5% good (GOS = 5) (shorter than 3 weeks' administration) and 22.5% unfavorable (GOS = 1-4) (longer than 3 weeks' administration). The duration of antibiotic treatment ranged from 4 to 43 days, and the mean therapy time was 19.74 ±7.32 days. Duration longer than 3 weeks for neonatal bacterial meningitis with negative CSF culture had no impact on prognosis. The unfavorable outcome group had more prenatal infections and premature rupture of membranes cases than the good outcome group. High CSF protein and CSF glucose and CSF cell count increase were associated with unfavorable outcome in 167 non-prenatal infection infants. High CSF cell count increase was associated with unfavorable outcome in 33 prenatal infection infants. In term infants, the positive rate of blood cultures was 24.5%.

CONCLUSIONS

Third generation cephalosporin therapy does not have a different prognosis for negative CSF culture of neonatal bacterial meningitis in term infants in this study.

Pharmacokinetics of antibacterial agents in the CSF of children and adolescents

The adequate management of central nervous system (CNS) infections requires that antimicrobial agents penetrate the blood-brain barrier (BBB) and achieve concentrations in the CNS adequate for eradication of the infecting pathogen. This review details the currently available literature on the pharmacokinetics (PK) of antibacterials in the CNS of children. Clinical trials affirm that the physicochemical properties of a drug remain one of the most important factors dictating penetration of antimicrobial agents into the CNS, irrespective of the population being treated (i.e. small, lipophilic drugs with low protein binding exhibit the best translocation across the BBB). These same physicochemical characteristics determine the primary disposition pathways of the drug, and by extension the magnitude and duration of circulating drug concentrations in the plasma, a second major driving force behind achievable CNS drug concentrations. Notably, these disposition pathways can be expected to change during the normal process of growth and development. Finally, CNS drug penetration is influenced by the nature and extent of the infection (i.e. the presence of meningeal inflammation). Aminoglycosides have poor CNS penetration when administered intravenously. Intrathecal gentamicin has been studied in children with more promising results, often exceeding the minimum inhibitory concentration. There are very limited data with intrathecal tobramycin in children. However, in the few patients that have been studied, the CSF concentrations were highly variable. Penicillins generally have good CNS penetration. Aqueous penicillin G reaches greater concentrations than procaine or benzathine penicillin. Concentrations remain detectable for ≥ 12 h. Of the aminopenicillins, both ampicillin and parenteral amoxicillin reach adequate CNS concentrations; however, orally administered amoxicillin resulted in much lower concentrations. Nafcillin and piperacillin are the final two penicillins with pediatric data: their penetration is erratic at best. Cephalosporins vary greatly in regard to their CSF penetration. Few first- and second-generation cephalosporins are able to reach higher CSF concentrations. Cefuroxime is the only exception and is usually avoided due to its adverse effects and slower sterilization of the CSF than third-generation agents. Ceftriaxone, cefotaxime, ceftazidime, cefixime and cefepime have been studied in children and are all able to adequately penetrate the CSF. As with penicillins, concentrations are greatest in the presence of meningeal inflammation. Meropenem and imipenem are the only carbapenems with pediatric data. Imipenem reaches higher CSF concentrations; however, meropenem is preferred due to its lower incidence of seizures. Aztreonam has also demonstrated favorable penetration but only one study has been completed in children. Both chloramphenicol and sulfamethoxazole/trimethoprim (cotrimoxazole) penetrate into the CNS well; however, significant toxicities limit their use. The small size and minimal protein binding of fosfomycin contribute to its favorable CNS PK. Although rarely used, it achieves higher concentrations in the presence of inflammation and accumulation is possible. Linezolid reaches high CSF concentrations; however, more frequent dosing might be required in infants due to their increased elimination. Metronidazole also has very limited information but it demonstrated favorable results similar to adult data; CSF concentrations even exceeded plasma concentrations at certain time points. Rifampin (rifampicin) demonstrated good CNS penetration after oral administration. Vancomycin demonstrates poor CNS penetration after intravenous administration. When combined with intraventricular therapy, CNS concentrations are much greater. Of the antituberculosis agents, isoniazid, pyrazinamide and streptomycin have been studied in children. Isoniazid and pyrazinamide have favorable CSF penetration. Streptomycin appears to produce unpredictable CSF levels. No pediatric-specific data are available for clindamycin, daptomycin, macrolides, tetracyclines, and fluoroquinolones. Daptomycin, fluoroquinolones, and tetracyclines have demonstrated favorable CNS penetration in adults; however, data are limited due to their potential pediatric-specific toxicities and newness within the marketplace. Macrolides and clindamycin have demonstrated poor CNS penetration in adults and thus have not been studied in pediatrics.

Pharmacokinetic changes in patients receiving extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation (ECMO) is a form of prolonged cardiopulmonary bypass used to temporarily sustain cardiac and/or respiratory function in critically ill patients. Extracorporeal membrane oxygenation further complicates the management of critically ill patients who already have profound physiologic derangements with consequent altered pharmacokinetics. The purpose of this study is to identify and critically review the published literature describing pharmacokinetics in the presence of ECMO. This review revealed a dearth of data describing pharmacokinetics during ECMO in critically ill adults, with most of the available data originating in neonates. Of concern, the present data indicate substantial variability and a lack of predictability in drug behavior in the presence of ECMO. The most common mechanisms by which ECMO affects pharmacokinetics are sequestration in the circuit, increased volume of distribution, and decreased drug elimination. While lipophilic drugs and highly protein-bound drugs (eg, voriconazole and fentanyl) are significantly sequestered in the circuit, hydrophilic drugs (eg, β-lactam antibiotics, glycopeptides) are significantly affected by hemodilution and other pathophysiologic changes that occur during ECMO. Although the published literature is insufficient to make any meaningful recommendations for adjusting therapy for drug dosing, this review systematically describes the available data enabling clinicians to make conclusions based on available data. Furthermore, this review serves to highlight the need for well-designed and conducted clinical and laboratory-based studies to provide the data from which robust dosing guidance can be developed to improve clinical outcomes in this most unwell cohort of patients.

Overton's rule helps to estimate the penetration of anti-infectives into patients' cerebrospinal fluid

In 1900, Ernst Overton found that the entry of anilin dyes through the cell membranes of living cells depended on the lipophilicity of the dyes. The brain is surrounded by barriers consisting of lipid layers that possess several inward and outward active transport systems. In the absence of meningeal inflammation, the cerebrospinal fluid (CSF) penetration of anti-infectives in humans estimated by the ratio of the area under the concentration-time curve (AUC) in CSF (AUC(CSF)) to that in serum (AUC(CSF)/AUC(S)) correlated positively with the lipid-water partition coefficient at pH 7.0 (log D) (Spearman's rank correlation coefficient r(S) = 0.40; P = 0.01) and negatively with the molecular mass (MM) (r(S) = -0.33; P = 0.04). The ratio of AUC(CSF) to the AUC of the fraction in serum that was not bound (AUC(CSF)/AUC(S,free)) strongly correlated with log D (r(S) = 0.67; P < 0.0001). In the presence of meningeal inflammation, AUC(CSF)/AUC(S) also correlated positively with log D (r(S) = 0.46; P = 0.002) and negatively with the MM (r(S) = -0.37; P = 0.01). The correlation of AUC(CSF)/AUC(S,free) with log D (r(S) = 0.66; P < 0.0001) was as strong as in the absence of meningeal inflammation. Despite these clear correlations, Overton's rule was able to explain only part of the differences in CSF penetration of the individual compounds. The site of CSF withdrawal (lumbar versus ventricular CSF), age of the patients, underlying diseases, active transport, and alterations in the pharmacokinetics by comedications also appeared to strongly influence the CSF penetration of the drugs studied.

Challenges in assessing microbial susceptibility and predicting clinical response to newer-generation fluoroquinolones

PURPOSE

To determine the most appropriate methods for assessing the potential effectiveness of the newer topical fluoroquinolones gatifloxacin, moxifloxacin, and besifloxacin.

METHODS

This article is based on a literature search for published articles about the pharmacokinetic (PK) and pharmacodynamic (PD) characteristics of and measure of bacterial susceptibility to topical ophthalmic fluoroquinolones. Search terms included fluoroquinolones, susceptibility, resistance, minimal/minimum inhibitory concentration (MIC), PDs, PKs, and ocular, ophthalmic, or topical antibiotics.

RESULTS

Topical fluoroquinolones, particularly besifloxacin, gatifloxacin, and moxifloxacin, have become important treatment options for common ocular bacterial infections due to their broad-spectrum bactericidal activity and low toxicity. An important challenge in ophthalmology is identifying the most accurate in vivo and in vitro methods for evaluating the efficacy of these topical fluoroquinolones. The MIC is the most commonly used measure of in vitro susceptibility. In systemic therapy, this measure is combined with PK data of antibiotics to generate PD indices PK/PD whose breakpoints differentiate clinically susceptible from nonsusceptible bacterial pathogen populations. PD breakpoints are further tested in prospective studies for their ability to predict clinical efficacy. However, it is not known whether systemically derived breakpoints apply to the assessment of clinical susceptibility to ocular agents. Topical ocular antibiotics likely achieve higher concentrations at the target site than do systemically administered antibiotics, but these higher concentrations can be quickly reduced by reflex tearing and blinking induced by instillation. Hence, studies have been conducted in animals and humans to determine the PK concentrations of topically administered antibiotics in ocular compartments. When combined with MIC values for topical pathogens, the results have the potential to predict clinical efficacy after identification of the appropriate PK/PD target. Ocular studies incorporating PK/PD assessments have recently begun to be reported with newer fluoroquinolones, including besifloxacin, gatifloxacin, and moxifloxacin, whose prolonged contact time and potent bactericidal activity have translated into some of the most favorable PK/PD target values. However, the clinical relevance of these studies has yet to be determined.

CONCLUSION

There is still a clear need for predictive models to extend our understanding of the clinical susceptibility of ocular pathogens.

5 versus 10 days of treatment with ceftriaxone for bacterial meningitis in children: a double-blind randomised equivalence study

BACKGROUND

Bacterial meningitis is an important cause of morbidity and mortality in developing countries, but the duration of treatment is not well established. We aimed to compare the efficacy of 5 and 10 days of parenteral ceftriaxone for the treatment of bacterial meningitis in children.

METHODS

We did a multicountry, double-blind, placebo-controlled, randomised equivalence study of 5 versus 10 days of treatment with ceftriaxone in children aged 2 months to 12 years with purulent meningitis caused by Streptococcus pneumoniae, Haemophilus influenzae type B, or Neisseria meningitidis. Our study was done in ten paediatric referral hospitals in Bangladesh, Egypt, Malawi, Pakistan, and Vietnam. We randomly assigned children who were stable after 5 days of treatment, through site-balanced computer-generated allocation lists, to receive a further 5 days of ceftriaxone or placebo. Patients, their guardians, and staff were masked to study-group allocation. Our primary outcomes were bacteriological failure or relapse. Our analysis was per protocol. This study is registered with the International Standard Randomised Controlled Trial Number Register, number ISRCTN38717320.

FINDINGS

We included 1004 of 1027 children randomly assigned to study groups in our analyses; 496 received treatment with ceftriaxone for 5 days, and 508 for 10 days. In the 5-day treatment group, two children (one infected with HIV) had a relapse; there were no relapses in the 10-day treatment group and there were no bacteriological failures in either study group. Side-effects of antibiotic treatment were minor and similar in both groups.

INTERPRETATION

In children beyond the neonatal age-group with purulent meningitis caused by S pneumoniae, H influenzae type b, or N meningitidis who are stable by day 5 of ceftriaxone treatment, the antibiotic can be safely discontinued.

FUNDING

United States Agency for International Development.

Penetration of drugs through the blood-cerebrospinal fluid/blood-brain barrier for treatment of central nervous system infections

The entry of anti-infectives into the central nervous system (CNS) depends on the compartment studied, molecular size, electric charge, lipophilicity, plasma protein binding, affinity to active transport systems at the blood-brain/blood-cerebrospinal fluid (CSF) barrier, and host factors such as meningeal inflammation and CSF flow. Since concentrations in microdialysates and abscesses are not frequently available for humans, this review focuses on drug CSF concentrations. The ideal compound to treat CNS infections is of small molecular size, is moderately lipophilic, has a low level of plasma protein binding, has a volume of distribution of around 1 liter/kg, and is not a strong ligand of an efflux pump at the blood-brain or blood-CSF barrier. When several equally active compounds are available, a drug which comes close to these physicochemical and pharmacokinetic properties should be preferred. Several anti-infectives (e.g., isoniazid, pyrazinamide, linezolid, metronidazole, fluconazole, and some fluoroquinolones) reach a CSF-to-serum ratio of the areas under the curves close to 1.0 and, therefore, are extremely valuable for the treatment of CNS infections. In many cases, however, pharmacokinetics have to be balanced against in vitro activity. Direct injection of drugs, which do not readily penetrate into the CNS, into the ventricular or lumbar CSF is indicated when other effective therapeutic options are unavailable.

Clinical Pharmacokinetics of Penicillins, Cephalosporins and Aminoglycosides in the Neonate: A Review

Bacterial infections are common in the neonates and are a major cause of morbidity and mortality. Sixty percent of preterm infants admitted to neonatal intensive care units received at least one antibiotic during the first week of life. Penicillins, aminoglycosides and cephalosporins comprised 53, 43 and 16%, respectively. Kinetic parameters such as the half-life (t1/2), clearance (Cl), and volume of distribution (Vd) change with development, so the kinetics of penicillins, cephalosporins and aminoglycosides need to be studied in order to optimise therapy with these drugs. The aim of this study is to review the pharmacokinetics of penicillins, cephalosporins and aminoglycosides in the neonate in a single article in order to provide a critical analysis of the literature and thus provide a useful tool in the hands of physicians. The bibliographic search was performed electronically using PubMed, as the search engine, until February 2nd, 2010. Medline search terms were as follows: pharmacokinetics AND (penicillins OR cephalosporins OR aminoglycosides) AND infant, newborn, limiting to humans. Penicillins, cephalosporins and aminoglycosides are fairly water soluble and are mainly eliminated by the kidneys. The maturation of the kidneys governs the pharmacokinetics of penicillins, cephalosporins and aminoglycosides in the neonate. The renal excretory function is reduced in preterms compared to term infants and Cl of these drugs is reduced in premature infants. Gestational and postnatal ages are important factors in the maturation of the neonate and, as these ages proceed, Cl of penicillins, cephalosporins and aminoglycosides increases. Cl and t1/2 are influenced by development and this must be taken into consideration when planning a dosage regimen with these drugs. More pharmacokinetic studies are required to ensure that the dose recommended for the treatment of sepsis in the neonate is evidence based.

Safety of ceftriaxone sodium at extremes of age

BACKGROUND

Isolated reports of neonatal and infant deaths associated with ceftriaxone-calcium precipitation in the lungs and kidneys have prompted a recommendation from the US FDA in June 2007 advising that in patients of all ages, calcium-containing solutions should not be administered simultaneously or within 48 h of the last ceftriaxone dose.

OBJECTIVE

To provide a comprehensive review of the literature surrounding the safety of ceftriaxone in the neonatal (< or = 28 days) and geriatric populations (> or = 65 years).

METHODS

Multi-database literature search for original research articles, review articles and case reports pertaining to safety of ceftriaxone in the neonatal and geriatric populations.

RESULTS/CONCLUSIONS

Ceftriaxone should be avoided or significantly minimized in neonates (especially those treated concomitantly with intravenous calcium solutions and those with hyperbilirubinemia), and potentially restricted in the geriatric population treated concomitantly with intravenous calcium.

Comparison of the probability of target attainment between ceftriaxone and cefepime in the cerebrospinal fluid and serum against Streptococcus pneumoniae

Although the disposition of ceftriaxone and cefepime in the cerebrospinal fluid (CSF) has been described, the ability of these agents to achieve critical pharmacodynamic targets against Streptococcus pneumoniae in CSF has not been reported. Plasma and CSF pharmacokinetic data were obtained from hospital patients with external ventricular drains and receiving ceftriaxone or cefepime. Concentration-time profiles in plasma and CSF were modeled using a 3-compartment model with 0-order infusion and 1st-order elimination and transfer. The model parameters were identified with population pharmacokinetic analysis (Big Non-Parametric Adaptive Grid with adaptive gamma). A Monte Carlo Simulation (9999 subjects) estimated the probability of target attainment (PTA) for total drug CSF concentrations at 50% and 100% T>MIC for ceftriaxone 2G IV Q12H and cefepime 2G IV Q8H. The S. pneumoniae bloodstream infection isolates from the SENTRY Antimicrobial Surveillance Program (USA) provided the distribution of contemporary (2003-2004) MICs. Post-Bayesian measures of bias and precision, observed-predicted plots, and R2 values were highly acceptable for both drugs. The probabilities of achieving 50% and 100% T>MIC in the CSF for ceftriaxone were 76% and 65%, respectively. For cefepime, the PTA at 50% and 100% T>MIC in the CSF were 91.8% and 82%, respectively. The CSF pharmacodynamics against S. pneumoniae for cefepime were superior to that of ceftriaxone. The implications of these findings need to be reexamined in the clinical setting.

New dosing strategies for antibacterial agents in the neonate

Dosing of antibiotics in neonates requires finding a delicate balance between maximal efficacy and minimal toxicity. There is a lack of data on efficacy of currently used antibiotics in neonates, and rational dosing therefore needs to be based on gestational- and postnatal-age-dependent pharmacokinetics in combination with surrogate markers. These surrogate markers are: (i) the area-under-the serum concentration time curve to minimum inhibitory concentration ratio (AUC/MIC); (ii) peak concentration to MIC ratio (Cmax/MIC); and (iii) the time the concentration remains above the MIC (T>MIC). Whereas the efficacy of beta-lactam antibiotics (including carbapenems) depends on T>MIC, the efficacy of most other antimicrobials (including aminoglycosides and fluoroquinolones) is related to AUC/MIC and Cmax/MIC. Most modern dosing regimens are adequate when these concentration effect relationships are taken into account. Dosing adjustments in neonates are suggested, based on these relationships. Several antimicrobial combinations for treatment of meningitis and necrotizing enterocolitis exist. Empiric treatment should be based on efficacy, concerns about resistance as well as information from institutional microbiological surveillance.

Population pharmacokinetics of arbekacin, vancomycin, and panipenem in neonates

Immature renal function in neonates requires antibiotic dosage adjustment. Population pharmacokinetic studies were performed to determine the optimal dosage regimens for three types of antibiotics: an aminoglycoside, arbekacin; a glycopeptide, vancomycin; and a carbapenem, panipenem. Eighty-three neonates received arbekacin (n = 41), vancomycin (n = 19), or panipenem (n = 23). The postconceptional ages (PCAs) were 24.1 to 48.4 weeks, and the body weights (BWs) ranged from 458 to 5,200 g. A one-compartment open model with first-order elimination was applied and evaluated with a nonlinear mixed-effect model for population pharmacokinetic analysis. In the fitting process, the fixed effects significantly related to clearance (CL) were PCA, postnatal age, gestational age, BW, and serum creatinine level; and the fixed effect significantly related to the volume of distribution (V) was BW. The final formulas for the population pharmacokinetic parameters are as follows: CL(arbekacin) = 0.0238 x BW/serum creatinine level for PCAs of <33 weeks and CL(arbekacin) = 0.0367 x BW/serum creatinine level for PCAs of > or = 33 weeks, V(arbekacin) = 0.54 liters/kg, CL(vancomycin) = 0.0250 x BW/serum creatinine level for PCAs of <34 weeks and CL(vancomycin) = 0.0323 x BW/serum creatinine level for PCAs of > or = 34 weeks, V(vancomycin) = 0.66 liters/kg, CL(panipenem) = 0.0832 for PCAs of <33 weeks and CL(panipenem) = 0.179 x BW for PCAs of > or = 33 weeks, and V(panipenem) = 0.53 liters/kg. When the CL of each drug was evaluated by the nonlinear mixed-effect model, we found that the mean CL for subjects with PCAs of <33 to 34 weeks was significantly smaller than those with PCAs of > or = 33 to 34 weeks, and CL showed an exponential increase with PCA. Many antibiotics are excreted by glomerular filtration, and maturation of glomerular filtration is the most important factor for estimation of antibiotic clearance. Clinicians should consider PCA, serum creatinine level, BW, and chemical features when determining the initial antibiotic dosing regimen for neonates.

Ceftriaxone: an update of its use in the management of community-acquired and nosocomial infections

Ceftriaxone is a parenteral third-generation cephalosporin with a long elimination half-life which permits once-daily administration. It has good activity against Streptococcus pneumoniae, methicillin-susceptible staphylococci, Haemophilus influenzae, Moraxella catarrhalis and Neisseria spp. Although active against Enterobacteriaceae, the recent spread of derepressed mutants which hyperproduce chromosomal beta-lactamases and extended-spectrum beta-lactamases has diminished the activity of all third-generation cephalosporins against these pathogens necessitating careful attention to sensitivity studies. Extensive data from randomised clinical trials confirm the efficacy of ceftriaxone in serious and difficult-to-treat community-acquired infections including meningitis, pneumonia and nonresponsive acute otitis media. Ceftriaxone also has efficacy in other community-acquired infections including uncomplicated gonorrhoea, acute pyelonephritis and various infections in children. In the nosocomial setting, extensive data also confirm the efficacy of ceftriaxone with or without an aminoglycoside in serious Gram-negative infections, pneumonia, spontaneous bacterial peritonitis and as surgical prophylaxis. Outpatient use of ceftriaxone, either as part of a step-down regimen or parenterally, is a distinguishing feature of the data gathered on the agent over the last decade. The review focuses on new applications of the drug and its use in infections in which the causative pathogens or their resistance patterns have changed over the past decade. Ceftriaxone has a good tolerability profile, the most common events being diarrhoea, nausea, vomiting, candidiasis and rash. Ceftriaxone may cause reversible biliary pseudolithiasis, notably at higher dosages of the drug (>/=2 g/day); however, the incidence of true lithiasis is <0.1%. Injection site discomfort or phlebitis can occur after intramuscular or intravenous administration.

CONCLUSIONS

As a result of its strong activity against S. pneumoniae, ceftriaxone holds an important place, either alone or as part of a combination regimen, in the treatment of invasive pneumococcal infections, including those with reduced beta-lactam susceptibility. Its once-daily administration schedule allows simplification of otherwise complex regimens in a hospital setting and has also contributed to its popularity as a parenteral agent in an ambulatory setting. These properties, together with a well characterised tolerability profile, mean that ceftriaxone is likely to retain its place as an important third-generation cephalosporin in the treatment of serious community-acquired and nosocomial infections.

The penetration of anti-infectives into the central nervous system

The blood-brain barrier, blood-cerebrospinal fluid (CSF) barrier, and meninges are a complex and difficult-to-study system charged with protecting the central nervous system (CNS) from toxins, including drugs. Current estimates of CNS drug exposure are limited to CSF to blood ratios, of which area-under-the curve (AUC) estimates provide the most robust measure of drug exposure. Different classes of drugs and individual drugs within classes have different CNS penetration potential that is dependent upon a variety of biologic and pharmacologic factors. Clinical data (AUC and point ratios) regarding the penetration of several anti-infective agents used for the treatment of CNS infections are provided in this article.

Efficacy of single-dose ceftriaxone in experimental otitis media induced by penicillin- and cephalosporin-resistant Streptococcus pneumoniae

We used a gerbil model of otitis media to assess the efficacy of single-dose ceftriaxone against three Streptococcus pneumoniae strains highly resistant to penicillin (MICs, 4 to 8 micrograms/ml) and with various susceptibilities to ceftriaxone (MICs, 0.5, 4, and 8 micrograms/ml). Middle ear infection was induced by bilateral transbullar challenge with 10(7) bacteria per ear. Antibiotic treatment was administered subcutaneously at 2 h postinfection. Infection status was checked 2 days later by counting the bacteria in middle ear and cerebrospinal fluid samples. With the cefriaxone-susceptible strain (MIC, 0.5 microgram/ml), we tested doses of 5 to 100 mg/kg of body weight. With a dose of 50 mg/kg, treatment outcome was equivalent to that with amoxicillin, which was used as a reference (25 mg/kg, two injections); no bacteria were recovered from 82% of the middle ear samples, and the rate of cerebrospinal fluid culture positivity was significantly reduced to 6%, relative to 59% for the untreated controls. Similar efficacy was obtained with a dose of 100 mg/kg against the two ceftriaxone-resistant strains. Pharmacokinetic study indicates that the values of the parameters in plasma after the administration of a dose of 100 mg/kg (peak level of total drug, 268 +/- 33 micrograms/ml; elimination half-life, 0.8 h; area under concentration-time curve, 488 micrograms.h.ml-1) were still suboptimal compared with the values of the parameters measured in pediatric patients after intravenous or intramuscular administration of a dose of 50 mg/kg. Our results indicate the efficacy of ceftriaxone against experimental cephalosporin-resistant pneumococcal otitis and provide a basis for the clinical use of single-dose ceftriaxone against pneumococcal otitis media.

beta-lactam antibiotics in the treatment of neuroborreliosis in children: preliminary results

In vitro beta-lactam antibiotics like ceftriaxone and penicillin G sodium have been shown to be active against Borrelia burgdorferi. Results of quantitative determinations of both antibiotic substances in the CSF for children are limited. Seventy-five children (median age 96 months, range 10 to 176 months) with probable or definite neuroborreliosis were treated with ceftriaxone (1 x 50-90 mg/kg/day) or penicillin G sodium (4 x 80,000-120,000 IU/kg/day) intravenously. On day 10 of therapy levels of penicillin G sodium (1,1.5,2,3,4, 5, or 6 h after i.v. administration), and ceftriaxone (1,2,4,6,12 or 24 h after i.v. administration) in serum and CSF were measured with a micro agar diffusion bioassay. Results demonstrate that after 5 h penicillin G sodium in CSF was above the minimal inhibitory concentration (MIC) but after 6 h penicillin G sodium levels were below the determination limit in 60% of the cases. All ceftriaxone results in CSF-even after 24 h-were above MIC. Penicillin G sodium serum values ranged from 46.6 to 0.1 mg/L (1 to 6 h post dose) and ceftriaxone serum values from 261 to 5 mg/l (1 to 24 h post dose). The role of penicillin G sodium and ceftriaxone and administration intervals of both antibiotics in the therapy of neuroborreliosis in children are discussed.

Cerebrospinal fluid penetration of amikacin in children with community-acquired bacterial meningitis

The penetration of amikacin into the cerebrospinal fluid (CSF) was studied with 16 children (mean age, 1 year and 9 months; range, 4 months to 8 years) with community-acquired bacterial meningitis. Amikacin was given intravenously at a dose of 7.5 mg/kg of body weight twice daily. CSF was collected on day 1, at the expected peak concentration of amikacin in CSF. The mean (standard deviation) concentration of amikacin in CSF was 1.65 (1.6) mg/liter. Concentrations of amikacin in CSF correlated significantly with CSF glucose levels on admission. The mean concentrations of amikacin in CSF were 2.9, 1.1, and 0.20 mg/liter in patients with CSF glucose levels of < 1, 1 to 2, and > 2 mmol/liter, respectively. Thus, amikacin penetrates the blood-brain barrier substantially in children with bacterial meningitis and achieves particularly high concentrations when CSF glucose level is < 1 mmol/liter on admission.

Concentrations of ceftriaxone in cerebrospinal fluid of children with meningitis receiving dexamethasone therapy

The penetration of ceftriaxone into cerebrospinal fluid (CSF) was studied with 11 children (mean age: 2 years, 4 months; range: 4 months to 8 years) with meningitis, receiving dexamethasone (0.15 mg/kg of body weight intravenously four times daily) as adjunctive therapy. Ceftriaxone was given intravenously at doses of 50 mg/kg twice daily to patients < 18 months old and 100 mg/kg once daily to patients > or = 18 months old. CSF was collected after 1 day of treatment at the expected peak concentration of ceftriaxone in CSF. Concentrations of ceftriaxone in CSF ranged from 0.7 to 9.2 mg/liter, with a mean value of 4.0 (standard deviation [SD], 2.9) mg/liter. Values were significantly higher for patients with CSF glucose levels of < 1 mmol/liter on admission to the hospital than for patients with CSF glucose levels of > or = 1 mmol/liter (mean values of 7.1 [SD, 2.2] mg/liter versus 2.2 [SD, 1.1] mg/liter; P < 0.001). After 1 day of treatment, ceftriaxone concentrations in the CSF of children receiving dexamethasone are similar to the mean values reported for children not treated with dexamethasone.

Ceftriaxone versus penicillin G in the short-term treatment of meningococcal meningitis in adults

Short-term treatment with ceftriaxone 2 g once daily for two days (group 1) was compared to treatment with a standard regimen of penicillin G (group 2) for six days in adults with meningococcal meningitis. Thirty-six patients were allocated in a randomized fashion to a treatment group: 16 to group 1 and 20 to group 2. The clinical and microbiological results were comparable in the two treatment groups. In both groups cultures of cerebrospinal fluid were sterile after 24 hours. One patient in each group died. In group 1 one case of fulminant meningococcemia and one case of brain abscess required further antibiotic treatment. It is concluded that short-term treatment with ceftriaxone is feasible but patients with severe forms of meningitis would not be eligible for treatment with this regimen, and careful follow-up of the patients receiving ceftriaxone is necessary.

Ceftriaxone--bilirubin-albumin interactions in the neonate: an in vivo study

The in vivo bilirubin-albumin binding interaction of ceftriaxone (CRO) was investigated in 14 non-jaundiced newborns, aged 33-42 weeks of gestation, during the first few days of life after they had reached stable clinical condition. CRO (50 mg/kg) was infused intravenously over 30 min. The competitive binding effect of CRO on the bilirubin-albumin complex was estimated by determining the reserve albumin concentration (RAC) at baseline, at the end of CRO infusion, and at 15 and 60 min thereafter. Immediately after the end of drug administration, RAC decreased from 91.9 (+/- 25.1) mumol/l to 38.6 (+/- 10.1) mumol/l (P = 0.0001). At the same time the plasma bilirubin toxicity index (PBTI) increased from 0.64 (+/- 0.40) before drug infusion to 0.96 (+/- 0.44) thereafter (P = 0.0001). The highest displacement factor (DF) was calculated to be 2.8 (+/- 0.6) at the end of drug infusion. Average total serum bilirubin concentrations decreased from a baseline value of 59.6 (+/- 27.0) mumol/l to 55.2 (+/- 27.1) mumol/l (P = 0.026). Sixty minutes after the end of CRO infusion, RAC was 58.3 (+/- 21.7) mumol/l, PBTI regained baseline, but DF was still 1.9 (+/- 0.2). No adverse events were recorded. Our results demonstrate significant competitive interaction of CRO with bilirubin-albumin binding in vivo. Thus, ceftriaxone should not be given to the neonate at risk of developing bilirubin encephalopathy.

Once-daily ceftriaxone to complete therapy of uncomplicated group B streptococcal infection in neonates. A preliminary report

Newborn infants minimally symptomatic with non-central nervous system (CNS) infections due to Streptococcus agalactiae (group B streptococcus [GBS]) and other pathogens may not require skilled nursing care during the entire course of parenteral antibiotic therapy. In 1985, treatment guidelines were made available to private practitioners in Oregon for therapy of newborn infants at low risk of complications from their infections. In 1988, patient data were collected and analyzed retrospectively. Outpatient management during convalescence of 51 infants (21 with culture-positive infections due to GBS) was accomplished with once-daily physician follow-up examinations and IM injection of ceftriaxone. Long-term (greater than or equal to two months) follow-up data were available for 67% of GBS-infected infants, with no complication of infection or significant complication of therapy reported. Outpatient parenteral antibiotic management of selected, low-risk infants may offer the clinician an alternative to hospitalization for a portion of the duration of parenteral antibiotic therapy.

Short course single daily ceftriaxone monotherapy for acute bacterial meningitis in children: results of a Swiss multicenter study. Part I: Clinical results

In a prospective Swiss multicenter study, 119 children (aged three weeks to 15.5 years) with acute bacterial meningitis were treated with single daily doses of ceftriaxone (100 mg/kg on days one and two and 60 mg/kg thereafter). All patients were randomly assigned to either short course (four, six, seven days) or full course (eight, 12, 14 days) therapy depending on whether they had contracted meningococcal, Haemophilus influenzae type b or pneumococcal meningitis. Bacteriological cure was obtained in 92 children who fully completed the study and in all the 20 culture-positive of the 27 children secondarily excluded from the study for failure to meet all bacteriological and initial safety criteria for continuation in protocol (secondary exclusions). Complete clinical recovery was noted in 105 of 119 patients (88%) and was as frequent in the short course (91%) as in the full course (89%), and as in the secondary exclusion (81%) group. All patients survived. At follow-up examination three to six months after hospital discharge only seven infants and seven children (11.8%), mostly those with poor presentation on admission (p = 0.0012), showed residual neurological sequelae. Side effects of antibiotic therapy were minor but more frequent, albeit not statistically significant (p = 0.065), in children receiving the full course therapy. The results of this study suggest that short course treatment of acute bacterial meningitis in children with single daily ceftriaxone monotherapy is as efficacious as full course therapy and at least as well tolerated.

Short course single daily ceftriaxone monotherapy for acute bacterial meningitis in children: results of a Swiss multicenter study. Part II: Bacteriological results

The in vitro activity of ceftriaxone, ampicillin and chloramphenicol was studied at a reference laboratory against the isolates of the first 33 patients enrolled in a pediatric Swiss Multicenter Meningitis Study. The predictive value of the MIC data of 31 of the strains was further corroborated by two sets of bacterial killing curves in broth supplemented with 2 g/l of albumin. Ceftriaxone had the lowest geometric mean MIC values against all groups of isolates except for ampicillin against Streptococcus agalactiae. The bactericidal activity of ceftriaxone and that of ampicillin, alone and in combination with chloramphenicol, was compared at six times the respective MICs and at pharmacologically readily achievable concentrations in cerebrospinal fluid. The bactericidal power of ceftriaxone at six times the MIC was as good or better than that of ampicillin alone or in combination against Neisseria meningitidis and Streptococcus pneumoniae despite the very low drug concentrations of ceftriaxone compared to that of the competitors; and it was barely lower at six times the MIC and at 1 mg/l (a level that is readily surpassed in CSF at the 24 h trough level after a single daily dose of ceftriaxone of 100 mg/kg (neonates 50 mg/kg) than that of ampicillin and chloramphenicol at much higher concentrations against Haemophilus influenzae type b.

Antimicrobial therapy for pediatric patients

New antimicrobial agents are being introduced for clinical use at an increasingly rapid rate. This has required physicians continually to review relevant data and determine unique properties that might guide selection among any new antibiotics as well as older ones. Efficacy, potential toxicity, and comparative cost (in that order) generally guide selection. The present comprehensive review examines currently available antibiotics along with some under investigation, emphasizing these three basic areas of consideration.

Ceftriaxone. A reappraisal of its antibacterial activity and pharmacokinetic properties, and an update on its therapeutic use with particular reference to once-daily administration

Since ceftriaxone was first reviewed in the Journal, further studies have confirmed its broad antibacterial spectrum in vitro and extended its clinical documentation in comparative studies with other widely used drugs in infections of the urinary and lower respiratory tract, meningitis in infants and children, uncomplicated gonorrhoea, perioperative prophylaxis in patients undergoing surgery, and in several other types of infection. As in earlier studies, which primarily used a twice-daily dosage regimen, few significant differences were found between therapeutic groups in comparative studies and results have demonstrated the efficacy of once-daily ceftriaxone in all but the most serious infections, such as sole antibiotic therapy in pseudomonal infections. Wider clinical experience has established that ceftriaxone is generally well tolerated. Thus, ceftriaxone now has a well-defined place as an appropriate alternative for the parenteral treatment of a variety of infections due to susceptible organisms, as well as for perioperative prophylaxis of surgery, and may offer advantages of greater convenience over other parenteral antibiotics which are administered more frequently.

Ceftriaxone: a third-generation cephalosporin

Ceftriaxone is a new third-generation cephalosporin with excellent activity against many gram-negative, and reasonable activity against most gram-positive microorganisms. Clinical studies have demonstrated its efficacy and safety in patients with bacterial meningitis; respiratory tract, urinary tract, soft tissue, bone and joint infections; and gonorrhea. Ceftriaxone has been well tolerated except for diarrhea, which in most cases has not required a change in therapy. The long elimination half-life of ceftriaxone has allowed twice- and once-daily administration, the latter potentially resulting in substantial cost savings. Because of its documented efficacy, safety, and convenient dosing schedule, ceftriaxone may become the preferred third-generation cephalosporin for the treatment of a variety of serious infections.

Clinical pharmacokinetics of the third generation cephalosporins

At the present time, the third generation cephalosporins that are already on the market or close to this point include cefsulodin, cefotaxime, cefoperazone, latamoxef, ceftriaxone, ceftazidime, ceftizoxime and cefotetan. Other newer compounds are also under development but have not been included in this review. None of the third generation compounds is suitable for oral administration and, accordingly, their pharmacokinetics have been studied only after intravenous and intramuscular administration. Microbiological assays and HPLC methods have been used for the measurement of plasma/serum, urine, bile and cerebrospinal fluid (CSF) concentrations. As found with cefotaxime, microbiological assays should only be used when the full metabolite spectrum of a particular drug is known, as otherwise, the presence of microbiologically active metabolites may lead to erroneous conclusions. Under normal conditions, the major route of elimination is via the kidneys for cefsulodin, latamoxef, ceftazidime, ceftizoxime and cefotetan. In contrast, cefoperazone is mainly eliminated in the bile, whereas cefotaxime and ceftriaxone depend both on the liver and the kidneys for their elimination. With the exception of ceftriaxone, which has a longer elimination half-life (i.e. around 8 hours), all the other third generation cephalosporins have a t1/2 ranging between 1.5 and 2.5 hours. Plasma protein binding is variable from one compound to another. However, the clinical relevance of this parameter is not clearly established since tissue penetration also depends on the relative affinity of the drug for tissue components. Third generation cephalosporins seem to penetrate adequately into the CSF and, thus pharmacokinetically appear to be appropriate agents for the treatment of meningitis. The degree of modification of pharmacokinetic parameters by renal insufficiency or hepatic diseases depends, as for other drugs, on the extent to which the compound is excreted via the kidneys or the liver. The third generation cephalosporins have been extensively studied under these conditions and recommendations for dosage modification in special circumstances are available for most of them. The pharmacokinetics of some third generation cephalosporins may be modified in neonates and elderly patients. Accordingly, their use at the extremes of age must be accompanied by a closer than usual clinical monitoring of the patient. From a clinical point of view, the third generation cephalosporins possess reliable pharmacokinetic properties.(ABSTRACT TRUNCATED AT 400 WORDS)