Ceftriaxone diffusion into cerebrospinal fluid of children with meningitis

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.

Ceftriaxone-induced Encephalopathy: A Pharmacokinetic Approach

We report a case of ceftriaxone-induced encephalopathy correlated with a high concentration of the drug in cerebrospinal fluid (CSF). Cephalosporin neurotoxicity is increasingly reported, especially in association with fourth-generation cephalosporins. The factors influencing CSF concentration are plasma concentration, liposolubility, ionization, molecular weight, protein binding and efflux. In our patient, high levels of ceftriaxone (27.9 mg/l) were found in CSF. β-Lactam-associated neurotoxicity is mainly due to similarities between GABA and the β-lactam ring. Because of differences in CSF/plasma ratios and blood-brain barrier efflux among patients, plasma drug monitoring cannot be used to estimate CSF concentration. As far as we know, this is the first reported case of ceftriaxone-induced encephalopathy associated with a high CSF concentration.

LEARNING POINTS

Ceftriaxone dose adjustment and clinical surveillance are strongly recommended in patients with renal failure.Measuring ceftriaxone cerebrospinal fluid concentration could be useful for confirming ceftriaxone-induced encephalopathy.

Development of Reverse Phase Ultra-fast Liquid Chromatography Using Ion-pairing Reagent for Quantitative Assessment of Ceftriaxone in Rat Serum and Cerebrospinal Fluid

Background:

In case of meningitis, the meninges are inflamed and the blood brain barrier is distorted, therefore, there is no hindrance to drug penetration. The problem arises when the disease is at the verge of cure, the meninges become uninflamed and the permeability of the drug is reduced to such extend that it becomes nearly impossible to maintain the minimum inhibitory concentration of drug at the site of infection. This problem was overcome by formulating ceftriaxone loaded NLCs and administrating it through intraperitoneal route to Wistar Albino rat. For quantitative assessment of drugs in rat serum and cerebrospinal spinal fluid, a new RP-UFLC (reverse-phase ultra-fast liquid chromatography) method has been developed and validated.

Objective:

Development and validation of RP-UFLC (using ion-pairing reagent) method for accurate estimation of ceftriaxone in rat serum and CSF.

Methods:

Method validation is done according to the ICH Guidelines (Q2) for the estimation of ceftriaxone in rat serum and its CSF (cerebrospinal fluid) by the RP-UFLC method. The blood was collected from the rat tail vein and CSF was collected carefully from cisterna magna of the rats by a 23G syringe. The mobile phase was used in a ratio of 70:30%v/v of phosphate buffer with ion-pairing reagent and acetonitrile with a pH of 8.0

Results:

Limit of detection and limit of quantification of ceftriaxone in rat serum was 1.08 μg/ml and 3.84 μg/ml, respectively. Similarly, the limit of detection and limit of quantification of ceftriaxone in CSF of rats was 0.94 μg/ml and 2.84 μg/ml, respectively. In both cases, the R2value was more than 0.99 and showed 99% accuracy.

Conclusion:

The experimental result suggests that the new RP-UFLC method developed and validated can be effectively used to assess ceftriaxone in preclinical studies in rats.

High-Dose Ceftriaxone for Bacterial Meningitis and Optimization of Administration Scheme Based on Nomogram

High dosages of ceftriaxone are used to treat central nervous system (CNS) infections. Dosage adaptation according to the glomerular filtration rate is currently not recommended. Ceftriaxone pharmacokinetics (PK) was investigated by a population approach in patients enrolled in a French multicenter prospective cohort study who received high-dose ceftriaxone for CNS infection as recommended by French guidelines (75 to 100 mg/kg of body weight/day without an upper limit). Only those with suspected bacterial meningitis were included in the PK analysis. A population model was developed using Pmetrics. Based on this model, a dosing nomogram was developed, using the estimated glomerular filtration rate (eGFR) and total body weight as covariates to determine the optimal dosage allowing achievement of targeted plasma trough concentrations. Efficacy and toxicity endpoints were based on previous reports, as follows: total plasma ceftriaxone concentrations of ≥20 mg/liter in >90% of patients for efficacy and ≤100 mg/liter in >90% of patients for toxicity. Based on 153 included patients, a two-compartment model including eGFR and total body weight as covariates was developed. The median value of the unbound fraction was 7.57%, and the median value of the cerebral spinal fluid (CSF)/plasma ratio was 14.39%. A nomogram was developed according to a twice-daily regimen. High-dose ceftriaxone administration schemes, used to treat meningitis, should be adapted to the eGFR and weight, especially to avoid underdosing using current guidelines. (This study has been registered at ClinicalTrials.gov under identifier NCT01745679.).

Systemic pharmacokinetics and cerebrospinal fluid uptake of intravenous ceftriaxone in patients with amyotrophic lateral sclerosis

The cephalosporin antibiotic ceftriaxone was evaluated as a potential therapeutic agent for the treatment of amyotrophic lateral sclerosis (ALS). The pharmacokinetics (PK) of ceftriaxone in plasma and cerebrospinal fluid (CSF) were investigated in 66 participants in a previously reported clinical trial. Their mean age was 51 years, and 65% were male. Participants were randomly assigned to 1 of 3 treatment groups receiving intravenous infusions (mean duration: 25 minutes) every 12 hours of either: placebo and placebo; 2 g ceftriaxone and placebo; or 2 g ceftriaxone twice. Mean steady-state plasma PK variables were: volume of distribution, 14 L (0.17 L/kg); elimination half-life, 8-9 h; total clearance, 17-21 mL/min (0.22-0.25 mL/min/kg). Values were not different between dosage groups. CSF PK analysis, determined through sparse CSF sampling, indicated apparent entry and elimination half-life values of 1.0 and 34 hours, respectively. With both dosage regimens, CSF concentrations were maintained above the target threshold of 1.0 µM (0.55 µg/mL) as determined from in vitro models. The plasma and CSF PK profiles of ceftriaxone were used as a basis for planning the Phase 3 clinical trial of ceftriaxone in ALS.

Clinical pharmacokinetics of antibacterials in cerebrospinal fluid

In the past 20 years, an increased discrepancy between new available antibacterials and the emergence of multidrug-resistant strains has been observed. This condition concerns physicians involved in the treatment of central nervous system (CNS) infections, for which clinical and microbiological success depends on the rapid achievement of bactericidal concentrations. In order to accomplish this aim, the choice of drugs is based on their disposition toward the cerebrospinal fluid (CSF), which is influenced by the physicochemical characteristics of antibacterials. A reduced distribution into CSF has been documented for beta-lactams, especially cephalosporins and carbapenems, on the basis of their hydrophilic nature. However, they represent a cornerstone of the majority of combined therapeutic schemes for their ability to achieve bactericidal concentrations, especially in the presence of inflamed meninges. The good tolerability of beta-lactams makes possible high daily dose intensities, which may be associated with increased probability of cure. Furthermore, the adoption of continuous infusion seems to be a fruitful option. Fluoroquinolones, namely moxifloxacin, and antituberculosis drugs, together with the agents such as linezolid, reach the highest CSF/plasma concentration ratio, which is greater than 0.8, and for most of these drugs it is near 1. For all drugs that are currently used for the treatment of CNS infections, the evaluation of pharmacokinetic/pharmacodynamic parameters, on the basis of dosing regimens and their time-dependent or concentration-dependent pattern of bacterial killing, remains an important aspect of clinical investigation and medical practice.

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.

Duration of In Vivo Antimicrobial Activity of Antibiotic-impregnated Cerebrospinal Fluid Catheters

OBJECTIVE:

Shunt infection is a major neurosurgical concern even after 50 years of experience with shunt surgery. Staphylococcus species are responsible for the majority of cerebrospinal fluid shunt infections. In vitro, antibiotic-impregnated cerebrospinal fluid shunt catheters (AIC) have demonstrated protection against multiple staphylococcus species and strains for reasonable periods. We aim to study the longevity of antimicrobial activity of AIC in vivo by using explanted catheters.

METHODS:

Twenty-five AICs (rifampicin [0.054%] and clindamycin [0.15%]) were explanted from 18 patients for noninfectious reasons, from 11 to 700 days postimplantation. The catheters were set up on standardized Staphylococcus aureus culture plates to detect antimicrobial activity. Unused fresh AIC segments were used as control in each culture plates.

RESULTS:

Fourteen explanted AICs demonstrated persistent antimicrobial activity against staphylococcal species. Antimicrobial activity was detected for a period of implantation up to 127 days. This is longer than that predicted by in vitro models.

CONCLUSION:

The persistent antimicrobial activity is likely to translate to ongoing in vivo antimicrobial protection. This period of protection exceeds that during which most shunt infections occur.

Killing activities of trovafloxacin alone and in combination with beta-lactam agents, rifampin, or vancomycin against Streptococcus pneumoniae isolates with various susceptibilities to extended-spectrum cephalosporins at concentrations clinically achievable in cerebrospinal fluid

The killing activities of trovafloxacin alone and in combination with beta-lactam agents (extended-spectrum cephalosporins, meropenem), rifampin, or vancomycin were evaluated against 20 genotypically characterized Streptococcus pneumoniae isolates for which amoxicillin MICs were >/=4 microg/ml (cefotaxime MICs, >/=4 microg/ml for six strains) at concentrations clinically achievable in cerebrospinal fluid. At 6 h the mean killing activity of trovafloxacin alone (range, 2.6 to 2.9 log(10) CFU/ml) did not vary significantly according to the susceptibility of the strains to beta-lactam agents. The activities of trovafloxacin or vancomycin added to the beta-lactam agents and the combination trovafloxacin-vancomycin were additive or indifferent. Against the ceftriaxone-resistant isolates, the killing activity of the combination of a beta-lactam agent and trovafloxacin did not differ significantly from that of a beta-lactam agent and vancomycin.

Pharmacokinetics and pharmacodynamics of antibiotics in meningitis

The penetration of antimicrobials into the CSF is dependent on lipid solubility, molecular size, capillary and choroid plexus efflux pumps, protein binding, and the degree of inflammation. Penicillins, certain cephalosporins, carbapenems, fluoroquinolones, vancomycin, and rifampin provide the highest ratios of CSF levels to the MBC for common infecting organisms. For beta-lactam antibiotics, it is the duration of time that CSF concentrations exceed the MBC that determines the rate of bactericidal activity. It appears that levels should exceed the MBC for more than 50% of the dosing interval. The peak/MBC and AUC/MBC ratios are important determinants of efficacy for aminoglycosides and fluoroquinolones. Once-daily dosing of aminoglycosides is as effective as multiple-daily dosing regimens in experimental meningitis, probably because of drug-induced prolonged persistent effects. Fluoroquinolones do not produce as prolonged persistent effects and are slightly less effective when administered once daily. Although steroid use can reduce the penetration and decrease the bactericidal activity of some antimicrobials, such as vancomycin, in experimental meningitis, the clinical impact of steroid use in human meningitis is still unclear.

Therapy for children with invasive pneumococcal infections. American Academy of Pediatrics Committee on Infectious Diseases

This statement provides guidelines for therapy of children with serious infections possibly caused by Streptococcus pneumoniae. Resistance of invasive pneumococcal strains to penicillin, cefotaxime, and ceftriaxone has increased over the past few years. Reports of failures of cefotaxime or ceftriaxone in the treatment of children with meningitis caused by resistant S pneumoniae necessitates a revision of Academy recommendations. For nonmeningeal infections, modifications of the initial therapy need to be considered only for patients who are critically ill and those who have a severe underlying or potentially immunocompromising condition or patients from whom a highly resistant strain is isolated. Because vancomycin is the only antibiotic to which all S pneumoniae strains are susceptible, its use should be restricted to minimize the emergence of vancomycin-resistant organisms. Patients with probable aseptic (viral) meningitis should not be treated with vancomycin. These recommendations are subject to change as new information becomes available.

In vitro killing activities of antibiotics at clinically achievable concentrations in cerebrospinal fluid against penicillin-resistant Streptococcus pneumoniae isolated from children with meningitis

We evaluated the in vitro killing activities of ceftriaxone, imipenem, vancomycin, gentamicin, fosfomycin, and rifampin, alone and in combination, against 26 Streptococcus pneumoniae strains (penicillin G MICs, > 0.125 to 2 micrograms/ml) isolated from the cerebrospinal fluid of children with meningitis. The antibiotics were tested at clinically achievable concentrations in cerebrospinal fluid. After 5 h of incubation, imipenem was the most effective drug. None of the combinations had synergistic activity. Killing by beta-lactam antibiotics or vancomycin was enhanced by the addition of gentamicin, reduced by the addition of rifampin, and unaffected by the addition of fosfomycin.

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.

Lipophilicity at pH 7.4 and molecular size govern the entry of the free serum fraction of drugs into the cerebrospinal fluid in humans with uninflamed meninges

Physicochemical properties of drugs were related to their ability to enter the cerebrospinal fluid (CSF) in humans by reevaluation of previously reported studies. Either the quotients of the drug concentrations in CSF and serum at steady state (CCSFSS/CSSS) or, since in most cases CSF passage was studied after a short-term infusion, the ratios of the areas under the concentration-time curves in CSF and serum (AUCCSF/AUCS) were taken as measures of CSF passage. AUCS and CSSS were corrected for binding to serum proteins (AUCSf, CSssf). Of the drugs studied the quotient of the octanol/water partition coefficient at pH 7.4 (PC) as a measure of lipophilicity and the square root of the molecular weight (MW1/2) correlated with AUCCSF/AUCS (Spearman's rank correlation coefficient rS = 0.78, P < 0.01) and with AUCCSF/AUCSf (rS = 0.90, P < 0.01). PC.MW-1/2 was related to AUCCSF/AUCSf (or CCSFSS/CSssf, respectively) by the equation: AUCCSF/AUCSf = 0.96 + 0.091.1n(PC.MW-1/2). For 0.0001 < or = PC.MW-1/2 < or = 1.0 this function may be of value for the prediction of CSF penetration in humans when the physicochemical properties of a drug are known and when active transport or metabolism are negligible.

Passage of cefotaxime and ceftriaxone into cerebrospinal fluid of patients with uninflamed meninges

Cefotaxime and ceftriaxone have proven to be effective in pyogenic infections of the central nervous system. Since in some bacterial central nervous system infections the blood-cerebrospinal fluid (CSF) barrier is either minimally impaired or recovers in the course of the illness, we studied the penetration of both antibiotics in the absence of inflamed meninges. Patients who had undergone external ventriculostomies for noninflammatory occlusive hydrocephalus received either cefotaxime (2 g/30 min) or ceftriaxone (2 g/30 min) to treat extracerebral infections. Serum and CSF were drawn repeatedly after the first dose. With ceftriaxone, they were also drawn after the last dose. The concentrations of cefotaxime, its metabolite desacetylcefotaxime, and ceftriaxone were determined by high-performance liquid chromatography with UV detection. Maximum concentrations of cefotaxime in CSF were reached 0.5 to 8 h (median = 3 h; n = 6) after the end of the infusion and ranged from 0.14 to 1.81 mg/liter (median = 0.44 mg/liter; n = 6). Maximum levels of ceftriaxone in CSF ranging from 0.18 to 1.04 mg/liter (median = 0.43 mg/liter; n = 5) were seen 1 to 16 h (median = 12 h; n = 5) after the infusion. The elimination half-life of cefotaxime in CSF was 5.0 to 26.9 h (median = 9.3 h; n = 5), and that of ceftriaxone was 15.7 to 18.4 h (median = 16.8 h; n = 3). It is concluded that after a single dose of 2 g, maximal concentrations of cefotaxime and ceftriaxone in CSF do not differ substantially. The long elimination half-lives guarantee uniform concentrations in CSF. These concentrations reliably inhibit highly susceptible bacteria but cannot be relied on to inhibit staphylococci and penicillin G-resistant Streptococcus pneumoniae.

Pharmacokinetic properties of the cephalosporins

Most cephalosporins can only be administered parenterally. Among agents that are absorbed from the gastrointestinal tract, those with bioavailabilities of 85 to 90% include cefroxadine, cefadroxil, cefsumide, cephalexin, cephradine, cephacetrile, and cefazaflur. Most cephalosporins are eliminated rapidly, with serum half-lives (t1/2s) of 1 to 2 hours. Exceptions are cefonicid with a t1/2 of 4.4 hours, cefpiramide with a t1/2 of 5.0 hours, and cefotetan with a t1/2 of 3.5 hours. The longest half-life is shown by ceftriaxone with a t1/2 of 8.5 hours. Cephalosporins are eliminated mostly by the kidneys, some with a substantial contribution from active tubular secretion, which is blocked by probenecid. The degree of metabolism varies. Only a few cephalosporins have a high biliary elimination. For example, with intravenously administered cefoperazone, about 70% appears in bile. High biliary elimination is also observed with cefmenoxime, ceftriaxone, cefbuperazone, and latamoxef (moxalactam). Because these are not appreciably absorbed from the gastrointestinal tract, the consequence is high intraintestinal concentrations of the drugs and a marked ensuing depression of the normal microflora with simultaneous emergence of resistant bacteria. The untoward ecological impact may even lead to Clostridium difficile-associated enterocolitis.

Cephalosporins in the treatment of meningitis

The synthesis of new cephalosporin antibiotics has provided agents which can effectively be used to treat most of the different forms of meningitis. None of the first generation cephalosporins can be considered acceptable as agents to treat meningitis. Cefuroxime can be used to treat meningitis due to Streptococcus pneumoniae, Haemophilus influenzae and Neisseria meningitidis in children. Agents such as cefotaxime and ceftriaxone are appropriate for neonatal meningitis due to Escherichia coli and group B streptococci, but not Listeria monocytogenes. Cefotaxime, ceftriaxone, ceftizoxime and ceftazidime have all proved effective as therapy of meningitis in children and adults when the pathogens are pneumococci, H. influenzae or N. meningitidis, but they have not been shown to yield an improved mortality or lower morbidity in spite of much greater cerebrospinal fluid (CSF) bactericidal titres. Cefotaxime, ceftizoxime, ceftriaxone and ceftazidime have been effective as therapy of meningitis due to E. coli, K. pneumoniae and Proteus species, but failures have occurred with all of the cephalosporins when used to treat meningitis due to Enterobacter spp. and Serratia marcescens. Only ceftazidime yields adequate CSF concentrations to treat meningitis due to Pseudomonas aeruginosa. Overall, the cephalosporins can now be considered a major component of the therapy of acute bacterial meningitis irrespective of the age group to be treated.

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.

Ceftriaxone: a beta-lactamase-stable, broad-spectrum cephalosporin with an extended half-life

Ceftriaxone is an aminothiazolyl-oxyimino cephalosporin. It possesses the typical in vitro activity of a third-generation cephalosporin with excellent activity against many gram-negative aerobic bacilli: Escherichia coli; species of Proteus, Klebsiella, Morganella, Providencia and Citrobacter; and Enterobacter agglomerans. Ceftriaxone also has outstanding bactericidal action against pneumococci, group B streptococci, meningococci, gonococci and Hemophilus influenzae. In healthy volunteers, it has an exceptionally long serum half-life of 5.8-8.7 (mean 6.5) hours. It distributes well throughout all body spaces, including cerebrospinal fluid in the presence of inflammation. Dosage modification is necessary only when there is combined hepatic and renal dysfunction. Adverse reactions characteristic of cephalosporins have been observed with the administration of ceftriaxone. No unique toxicities have been identified, and hypoprothrombinemic bleeding is not part of the adverse reaction profile. Ceftriaxone has been used to treat serious bacterial infections in neonates, infants, children and adults. Bacteriologic and clinical success rates have consistently exceeded 90%. The drug has also been used as single-dose chemoprophylaxis in coronary artery bypass, biliary tract, vaginal hysterectomy and prostatic surgery. Efficacy and safety were similar to multiple-dose cefazolin. Ceftriaxone warrants special consideration because its extended half-life allows for less frequent dosing than other antimicrobials. Significant cost savings can be realized with proper use of this antibiotic.

Comparison of ceftriaxone and ampicillin plus chloramphenicol for the therapy of acute bacterial meningitis

Ceftriaxone, a new third-generation cephalosporin, appears to be promising for the therapy of acute bacterial meningitis. The 90% MBCs of ceftriaxone against 54 recent cerebrospinal fluid isolates of Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae were less than or equal to 0.06 to 0.25 micrograms/ml. We examined the efficacy and safety of ceftriaxone therapy of meningitis in Bahia, Brazil. The study was conducted in two phases; in phase A, ceftriaxone was coadministered with ampicillin. The mean cerebrospinal fluid concentrations of ceftriaxone 24 h after an intravenous dose of 80 mg/kg were 4.2 and 2.3 micrograms/ml on days 4 to 6 and 10 to 12 of therapy, respectively. These concentrations were 8- to more than 100-fold greater than the 90% MBCs against the relevant pathogens. In phase B, ceftriaxone (administered once daily at a dose of 80 mg/kg after an initial dose of 100 mg/kg) was compared with conventional dosages of ampicillin and chloramphenicol in a prospective randomized trial of 36 children and adults with meningitis. The groups were comparable based on clinical, laboratory, and etiological parameters. Ceftriaxone given once daily produced results equivalent to those obtained with ampicillin plus chloramphenicol, as judged by cure rate, case fatality ratio, resolution with sequelae, type and severity of sequelae, time to sterility of cerebrospinal fluid, and potentially drug-related adverse effects. The cerebrospinal fluid bactericidal titers obtained 16 to 24 h after ceftriaxone dosing were usually 1:512 to greater than 1:2,048 even late in the treatment course, compared with values of 1:8 to 1:32 in patients receiving ampicillin plus chloramphenicol. Ceftriaxone clearly deserves further evaluation for the therapy of meningitis; the optimal dose, dosing frequency (every 12 h or every 24 h), and duration of therapy remain to be determined.

Role of cephalosporins in the treatment of bacterial meningitis in adults. Overview with special emphasis on ceftazidime

Experience with the use of first-generation cephalosporins in bacterial meningitis has been disappointing; low concentrations were obtained in the cerebrospinal fluid, and therapeutic failures were encountered. Of the second-generation cephalosporins cefamandole, cefuroxime, and cefoxitin, only cefuroxime has proved efficacy in meningitis caused by meningococci, pneumococci, or Hemophilus influenzae. The third-generation cephalosporins offer new advantages in the treatment of meningitis because they are active at the cerebrospinal fluid concentrations obtainable. Cefotaxime has produced high cure rates in patients with meningitis caused by meningococci, pneumococci, or H. influenzae. Several controlled comparative studies indicate that ceftriaxone is as effective as conventional treatment in therapy for neonatal or childhood meningitis caused by Streptococcus agalactiae, Escherichia coli, or H. influenzae. Moxalactam has been found in uncontrolled studies to be effective when the cause was enteric gram-negative bacilli. Ceftazidime is a new cephalosporin with a high degree of beta-lactamase stability and a broad antibacterial spectrum, which includes Pseudomonas aeruginosa that enters the cerebrospinal fluid. Data from 29 patients who received ceftazidime as monotherapy for bacterial meningitis showed an overall cure or improvement rate of 75.9 percent. Therapy failed in three patients with meningitis caused by gram-positive organisms (Staphylococcus aureus, S. epidermidis, S. agalactiae), and in three with gram-negative organisms. Of 14 patients with Pseudomonas meningitis, 11 showed a cure, as did six of six patients with meningitis caused by Enterobacter, Serratia, or Acinetobacter. More, preferably controlled, studies of the efficacy of ceftazidime in the treatment of meningitis should be undertaken.

[Pharmacokinetics and tissue penetration of ceftriaxone]

This article describes the pharmacokinetics of ceftriaxone, a new "third generation" cephalosporin. This antibiotic displays two major characteristics: a very long serum half-life and a good tissue penetration. The properties of ceftriaxone should allow its easy clinical handling.

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)

Rationale for optimal dosing of beta-lactam antibiotics in therapy for bacterial meningitis

This review considers the five major principles governing optimal dosing of beta-lactam antibiotics in therapy for bacterial meningitis: off the entry of passage of antibiotics into CSF, (2) the antimicrobial activity of beta-lactams within the purulent CSF in vivo, (3) the bactericidal activity within the CSF, (4) the route and mode of drug administration together with the postantibiotic effect, and (5) the duration of therapy. Special attention is paid to the third principle, bactericidal activity within the CSF, employing the model of the newer, third-generation cephalosporins used in the treatment of meningitis caused by gram-negative aerobic bacilli.

Pharmacokinetics of ceftriaxone in neonates and infants with meningitis

The pharmacokinetics of ceftriaxone was studied in the plasma, urine, and cerebrospinal fluid of seven neonates and seven infants with meningitis. In addition, plasma and urine data were obtained in five neonates and one infant receiving ceftriaxone for other serious infections. All neonates younger than 14 days received daily doses of 50 mg/kg ceftriaxone; all other patients but two received 100 mg/kg. The average weight-corrected values for total body clearance (ClT), volume of distribution (Vdss), and biologic half-life (t 1/2) were 0.37 ml/min/kg, 0.45 L/kg, and 16.2 hours in neonates younger than 1 week; 0.77 ml/min/kg, 0.48 L/kg, and 9.2 hours in neonates older than 1 week; and 1.03 ml/min/kg, 0.39 L/kg, and 7.1 hours in older infants, respectively. There was a significant difference in ClT and t 1/2 between the neonates younger and both neonates older than 1 week, and infants. The Vdss was not significantly different among the three age groups. The average renal clearance in neonates younger than 1 week (0.28 ml/min/kg was 70%, in neonates older than 1 week (0.54 ml/min/kg) was 77%, and in older infants (0.49 ml/min/kg) was 47% of ClT, indicating that nonrenal elimination was less developed in neonates. The quantitation of CSF diffusion of ceftriaxone was assessed by comparison of the areas under the CSF and plasma concentration-time curve. The mean ceftriaxone penetration into the CSF in neonates and infants with bacterial meningitis was 17%. On the other hand, penetration in patients with aseptic meningitis amounted to only 4%. Mean ceftriaxone concentrations in the CSF in patients with bacterial meningitis were 2.8 mg/L after 24 hours, exceeding by many times the minimum inhibitory concentration of the common meningitis pathogens at this time.

Ceftriaxone. A review of its antibacterial activity, pharmacological properties and therapeutic use

Ceftriaxone is a new 'third generation' semisynthetic cephalosporin with a long half-life which has resulted in a recommended once daily administration schedule. It is administered intravenously or intramuscularly and has a broad spectrum of activity against Gram-positive and Gram-negative aerobic, and some anaerobic, bacteria. The activity of ceftriaxone is generally greater than that of the 'first' and 'second generation' cephalosporins against Gram-negative bacteria, but less than that of the earlier generations of cephalosporins against many Gram-positive bacteria. Although ceftriaxone has some activity against Pseudomonas aeruginosa, on the basis of present evidence it cannot be recommended as sole antibiotic therapy in pseudomonal infections. Ceftriaxone has been effective in treating infections due to other 'difficult' organisms such as multidrug-resistant Enterobacteriaceae. Ceftriaxone was effective in complicated and uncomplicated urinary tract infections, lower respiratory tract infections, skin, soft tissue, bone and joint infections, bacteraemia/septicaemia, and paediatric meningitis due to susceptible organisms. In most of these types of infections once-daily administration appears efficacious. Results were also encouraging in a few patients with ear, nose and throat, intra-abdominal, obstetric and gynaecological infections, and adult meningitis, but conclusions are not yet possible as to the efficacy of the drug in these indications due to limited experience. A single intramuscular dose of ceftriaxone has been compared with standard therapy for gonorrhoea due to non-penicillinase-producing and penicillinase-producing strains of Neisseria gonorrhoeae and shown to be highly effective. In a few small trials the comparative efficacy of ceftriaxone and other antibacterials has been assessed in other types of infections and in perioperative prophylaxis in patients undergoing surgery. Few significant differences in response rates were found between therapeutic groups in these comparative studies, but larger well-designed studies are needed to more clearly assess the comparative efficacy of ceftriaxone and other antimicrobials, especially the aminoglycosides and other 'third generation' cephalosporins, and to confirm the apparent lack of serious side effects with ceftriaxone. If more widespread use confirms the safety and efficacy of ceftriaxone, it will offer an important alternative, particularly for the treatment of serious infections due to multidrug-resistant Gram-negative bacteria and in situations where the long half-life of the drug could result in worthwhile convenience and cost benefits.

Comparison of ceftriaxone and traditional therapy of bacterial meningitis

Forty-five children (aged 1 day to 15 years) with bacterial meningitis were randomized to receive either traditional therapy (ampicillin and chloramphenicol or gentamicin, pending sensitivity) or ceftriaxone (100 mg/kg per day in two doses for a minimum of 10 days). The etiological agents involved were similar for the two groups and included Haemophilus influenzae type b, Neisseria meningitidis, Streptococcus pneumoniae, and group B streptococcus. Repeat spinal taps were carried out 24 to 48 h after admission. Organisms were seen on the Gram stain of one patient treated with ceftriaxone, but five patients in the traditional therapy group had organisms present on Gram stain of uncentrifuged spinal fluid or positive cultures of the spinal fluid (or both). Ceftriaxone entered the cerebrospinal fluid well, and the average cerebrospinal fluid bactericidal activity for ceftriaxone 1 h after a dose was at least 60 times greater than for ampicillin or chloramphenicol. In those patients who received treatment for a long enough period of time to permit evaluation, there was one death in each group, both due to S. pneumoniae. The length of fever and complications were similar for the patients in both groups. Ceftriaxone was well tolerated; diarrhea, seen in 5 of the 22 patients who received the drug, was the most commonly encountered adverse effect. It was mild, and in no case was it necessary to discontinue the drug. Ceftriaxone appears in this preliminary study to be a safe and acceptable single agent for the treatment of bacterial meningitis in children.

Effect of inoculum size on Haemophilus influenzae type b susceptibility to new and conventional antibiotics

Thirty-three Haemophilus influenzae type b isolates, including beta-lactamase acetyltransferase-positive strains, were tested by microtiter broth dilution for susceptibility to eight beta-lactam compounds and chloramphenicol. All antibiotics except ampicillin and chloramphenicol were highly bactericidal against all isolates at an inoculum of 10(5) CFU/ml. However, at an inoculum of 10(5) CFU/ml, the minimal bactericidal concentrations of all drugs except ceftriaxone were above levels usually achievable in cerebrospinal fluid. Results of time-kill studies confirmed this inoculum effect. In vivo studies are needed to test the clinical impact of these observations.