Kinetic disposition of intravenous ceftriaxone in normal subjects and patients with renal failure on hemodialysis or peritoneal dialysis

Physiologically-based pharmacokinetic modeling for single and multiple dosing regimens of ceftriaxone in healthy and chronic kidney disease populations: a tool for model-informed precision dosing

Introduction: Ceftriaxone is one of commonly prescribed beta-lactam antibiotics with several label and off-label clinical indications. A high fraction of administered dose of ceftriaxone is excreted renally in an unchanged form, and it may accumulate significantly in patients with impaired renal functions, which may lead to toxicity. Methods: In this study, we employed a physiologically-based pharmacokinetic (PBPK) modeling, as a tool for precision dosing, to predict the biological exposure of ceftriaxone in a virtually-constructed healthy and chronic kidney disease patient populations, with subsequent dosing optimizations. We started developing the model by integrating the physicochemical properties of the drug with biological system information in a PBPK software platform. A PBPK model in an adult healthy population was developed and evaluated visually and numerically with respect to experimental pharmacokinetic data. The model performance was evaluated based on the fold error criteria of the predicted and reported values for different pharmacokinetic parameters. Then, the model was applied to predict drug exposure in CKD patient populations with various degrees of severity. Results: The developed PBPK model was able to precisely describe the pharmacokinetic behavior of ceftriaxone in adult healthy population and in mild, moderate, and severe CKD patient populations. Decreasing the dose by approximately 25% in mild and 50% in moderate to severe renal disease provided a comparable exposure to the healthy population. Based on the simulation of multiple dosing regimens in severe CKD population, it has been found that accumulation of 2 g every 24 h is lower than the accumulation of 1 g every 12 h dosing regimen. Discussion: In this study, the observed concentration time profiles and pharmacokinetic parameters for ceftriaxone were successfully reproduced by the developed PBPK model and it has been shown that PBPK modeling can be used as a tool for precision dosing to suggest treatment regimens in population with renal impairment.

Comparison of antimicrobial dosing recommendations in patients receiving intermittent hemodialysis among drug information resources

WHAT IS KNOWN AND OBJECTIVE

Tertiary drug information resources are frequently consulted for the optimal antimicrobial dosing in intermittent hemodialysis (IHD) patients. Yet, significant discrepancy may exist in dosing recommendations between resources. This study was to evaluate the consistency of antimicrobial dosing recommendations in IHD among four different drug information resources and the relevance of referenced pharmacokinetic studies.

METHODS

Dosing recommendations of 29 commonly prescribed antimicrobials in IHD patients were collected from Micromedex, LexiComp, Clinical Pharmacology and Drug Prescribing in Renal Impairment to compare dosing categorization and the total daily dose (TDD). Significant dosing discrepancies were defined as ≥30% difference. Referenced pharmacokinetic studies were evaluated for their relevance in current practice, using sample size, hemodialyzer types, the use of optimal pharmacodynamic targets and the consideration of different interdialytic dosing periods.

RESULTS AND DISCUSSION

A significant variation was found both in dosing categorization and recommended doses between resources. Seventeen drugs were compared for TDD with significant dosing discrepancy in 8 drugs. Among 42 referenced pharmacokinetic studies, 40 were evaluated. Mean patient numbers of pharmacokinetic studies were 13 ranging from 3 to 70. Sixty per cent of studies utilized contemporary hemodialyzers (e.g., high-flux and/or high efficiency). The optimal pharmacodynamic targets and the impact of different interdialytic intervals were assessed only in 27.5% and 7.5% respectively.

WHAT IS NEW AND CONCLUSION

Inconsistent antimicrobial dosing recommendations for IHD patients exist among four well-established resources. Many referenced pharmacokinetic studies utilized outdated or less pharmacodynamically relevant study methods. Newer studies are warranted to reflect contemporary dialysis practice and assess its impact on optimal antimicrobial dosing.

Ceftriaxone-induced acute encephalopathy in a peritoneal dialysis patient

Encephalopathy is a rare side effect of third and fourth generation cephalosporins. Renal failure and preexisting neurological disease are notable risk factors. Recognition is important as discontinuing the offending agent usually resolves symptoms. We present a case of acute encephalopathy in a patient with end stage renal disease (ESRD) treated with peritoneal dialysis (PD) who received intravenous ceftriaxone for peritonitis. This case illustrates the potential severe neurologic effects of cephalosporins, which are recommended by international guidelines as first-line antimicrobial therapy for spontaneous bacterial peritonitis.

Pharmacokinetic parameters of ceftriaxone after single intravenous and intramuscular administration in camels (Camelus Dromedarius)

The purpose of this study was to investigate the plasma disposition kinetics of ceftriaxone in female camels (n=5) following a single intravenous (i.v.) bolus or intramuscular (i.m.) injections at a dosage of 10mg kg(-1) body weight in all animals. A crossover design was carried out in two phases separated by 15 days. Jugular blood samples were collected serially for 48h and the plasma was analysed by high-performance liquid chromatography (HPLC). Following single i.v. injections the plasma concentration time curves of ceftriaxone were best fitted to a two-compartment model. The drug was rapidly distributed with half-life of distribution t(1/2alpha) of 0.24+/-0.01h and moderately eliminated with elimination rate constant and elimination half-life of 0.27+/-0.13h(-1) and 2.57+/-0.52h, respectively. The volume of distribution at steady state (V(dss)) was 0.32+/-0.01lkg(-1) and the total body clearance (Cl(tot)) was 0.11+/-0.01lkg(-1)h(-1), respectively. Following i.m. administration, the mean T(max), C(max), t(1/2el) and AUC values for plasma data were 1.03+/-0.23h, 21.54+/-2.61microg ml(-1), 1.76+/-0.03h and 85.82+/-11.21microg ml(-1)h(-1), respectively. The i.m. bioavailability was 93.42+/-21.4% and the binding percentage of ceftriaxone to plasma protein was moderate, ranging from 33% to 42% with an average of 34.5%.

Pharmacokinetics of ceftriaxone after intravenous, intramuscular and subcutaneous administration to domestic cats

The pharmacokinetic properties of ceftriaxone, a third-generation cephalosporin, were investigated in five cats after single intravenous, intramuscular and subcutaneous administration at a dosage of 25 mg/kg. Ceftriaxone MICs for some gram-negative and positive strains isolated from clinical cases were determined. Efficacy predictor (t > MIC) was calculated. Serum ceftriaxone disposition was best fitted by a bicompartmental and a monocompartmental open models with first-order elimination after intravenous and intramuscular and subcutaneous dosing, respectively. After intravenous administration, distribution was fast (t1/2d 0.14 +/- 0.02 h) and moderate as reflected by the volume of distribution (V(d(ss))) of 0.57 +/- 0.22 L/kg. Furthermore, elimination was rapid with a plasma clearance of 0.37 +/- 0.13 L/h.kg and a t1/2 of 1.73 +/- 0.23 h. Peak serum concentration (Cmax), tmax and bioavailability for the intramuscular administration were 54.40 +/- 12.92 microg/mL, 0.33 +/- 0.07 h and 85.72 +/- 14.74%, respectively; and for the subcutaneous route the same parameters were 42.35 +/- 17.62 microg/mL, 1.27 +/- 0.95 h and 118.28 +/- 39.17%. Ceftriaxone MIC for gram-negative bacteria ranged from 0.0039 to >8 microg/mL and for gram-positive bacteria from 0.5 to 4 microg/mL. t > MIC was in the range 83.31-91.66% (10-12 h) of the recommended dosing interval (12 h) for Escherichia coli (MIC90 = 0.2 microg/mL).

Daily variations in ceftriaxone pharmacokinetics in rats

The aim of this study was to determine whether the time of day ceftriaxone was administered modified its pharmacokinetics. Ceftriaxone was given intraperitoneally at either 0400, 1000, 1600, and 2200 h to Sprague-Dawley rats synchronized under a light-dark cycle of 12 h of light and 12 h of dark. Pharmacokinetic parameters were analyzed for the presence of a 24-h rhythm. Results showed significant daily variations (P < 0.05) in ceftriaxone clearance, with the highest values during the dark phase. It is concluded that time-dependent variations in ceftriaxone pharmacokinetics may affect the therapeutic efficacy of current once-daily dosing schedules.

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.

Pharmacokinetics of ceftriaxone administered by the intravenous, intramuscular or subcutaneous routes to dogs

The purpose of this study was to investigate the pharmacokinetics of ceftriaxone after single intravenous (i.v.), intramuscular (i.m.) and subcutaneous (s.c.) doses in healthy dogs. Six mongrel dogs received ceftriaxone (50 mg/kg) by each route in a three-way crossover design. Blood samples were collected in predetermined times after drug administration. Results are reported as mean +/- standard deviation (SD). Total body clearance (Cl(t)) and apparent volume of distribution (V(z)) for the i.v. route were 3.61 +/- 0.78 and 0.217 +/- 0.03 mL/kg, respectively. Terminal half-life harmonic mean (t(1/2 lambda)) was 0.88; 1.17 and 01.73 h for the i.v., i.m and s.c. routes, respectively. Mean peak serum concentration (C(max)) was 115.10 +/- 16.96 and 69.28 +/- 14.55 microg/mL for the i.m and s.c. routes, respectively. Time to reach C(max) (t(max)) was 0.54 +/- 0.24 and 1.29 +/- 00.64 h for the i.m and s.c. routes, respectively. Mean absorption time (MAT) was 1.02 +/- 0.64 and 2.23 +/- 00.73 h for the i.m and s.c. routes, respectively. Bioavailability was 102 +/- 27 and 106 +/- 14% for the i.m and s.c. routes, respectively. Statistically significant differences were determined in C(max), t(max), MAT and t(1/2 lambda) of s.c. administered ceftriaxone when compared with the i.v and i.m. routes. These findings suggest that once or twice s.c. or i.m. daily administered ceftriaxone should be adequate to treat most susceptible infections in dogs.

Pharmacological properties of parenteral cephalosporins: rationale for ambulatory use

Parenteral cephalosporins are among the most frequently used antibiotics in hospital therapy. They are characterised by an extended spectrum of activity against gram-positive and gram-negative bacteria, and some also have good activity against anaerobes. They kill proliferating bacterial cells rapidly, and generally show only a low tendency to select resistant mutants. However, there are cephalosporin compounds which induce cephalosporinases very rapidly in certain microorganisms. Together with other beta-lactam antibiotics, parenteral cephalosporins interfere with bacterial cell wall synthesis by inhibiting peptidoglycan cross-linkage. Because of this specific target, they are nontoxic to mammalian cells, and have a very favourable adverse effect profile. The chemical stability of parenteral cephalosporins in aqueous solution is good. After intravenous injection, high concentrations of these agents are achieved in serum and tissue. Most cephalosporins are eliminated unchanged via the kidney, with a half-life of 1 to 2 hours. But there are also derivatives with a serum half-life of more than 2 and up to 8 hours, allowing 12- or 24-hour dosage intervals. Because of their reliable efficacy and low risk of adverse effects, the parenteral cephalosporins offer a high degree of tolerability even in the setting of outpatient antibiotic therapy. In particular, the derivatives of the third generation are characterised by unique pharmacological properties.

Determination of unbound ceftriaxone in rat blood by on-line microdialysis and microbore liquid chromatography

In vivo microdialysis was used to determine unbound ceftriaxone in rat blood. A microdialysis probe was inserted into the jugular vein/right atrium of Sprague-Dawley rats, and dose of 10 mg/kg ceftriaxone was then administered via the femoral vein. Dialysates were automatically collected and injected into a liquid chromatographic system via an on-line injector. Isocratic elution of ceftriaxone within 10 min was achieved using a microbore liquid chromatographic system. The chromatographic mobile phase consisted of methanol-100 mM monosodium phosphoric acid (15:85, v/v, pH 7.0). The wavelength of the UV detector was set at 280 nm. Intra- and inter-assay accuracy and precision of the assay were less than 15%. The detection limit of ceftriaxone was 20 ng/ml. The results suggest that unbound ceftriaxone in rat blood is best fit to a biexponential decay model.

Determination of third-generation cephalosporins by high-performance liquid chromatography in connection with pharmacokinetic studies

The third-generation cephalosporins are semisynthetic beta-lactam antibiotics, including several oral and parental agents with extended activity against Gram-negative pathogens. They are generally determined either by microbiological techniques or by high-performance liquid chromatography (HPLC). The major drawback or bioassays is the lack of specificity, especially when a biotransformation of the cephalosporin molecule leads to active metabolites, or when the antibacterial therapy is based on association with drugs. Thus, for many years, numerous reversed-phase HPLC procedures have been proposed to overcome these difficulties. This review presents different HPLC methods proposed for the quantification in biological fluids of fourteen third-generation cephalosporins, ranged between parenteral and oral compounds. The sensitivity and specificity of these chromatographic procedures are discussed with regard to the pharmacokinetic properties of the antibiotics studied.

Clinical pharmacokinetics of antibiotics in patients with impaired renal function

Many antibiotics are eliminated renally and dosage adjustments are commonly made in patients with renal insufficiency. This is a critical review of antibiotic pharmacokinetics in patients with various degrees of renal function. Detailed information regarding pharmacokinetic alterations with specific antibiotics or antibiotic classes has been compiled and tabulated. From pharmacokinetic evidence, recommendations for dosage adjustments of antibiotics are supplied. The criteria used for assigning rating levels to specific pharmacokinetic articles as well as the grading system for dosage adjustments are outlined. In addition, a basic review of pharmacokinetic alterations in renal failure and factors affecting the removal of drugs by haemodialysis is included.

Lack of probenecid effect on nonrenal excretion of ceftriaxone in anephric patients

Probenecid has been shown to decrease renal and biliary excretion of organic acids. In a randomized crossover study, the effect of coadministered probenecid on nonrenal excretion of ceftriaxone was studied in six functionally anephric patients in whom ceftriaxone is eliminated exclusively by nonrenal or presumably by biliary excretion. Each patient received 0.5 g IV ceftriaxone without and with probenecid (0.5 g at 10 and 2 hours prior to ceftriaxone and 0.5 g q12h X 3 doses post ceftriaxone). Serial blood samples were collected over 48 hours and plasma analyzed for ceftriaxone by high performance liquid chromatography (HPLC). Pharmacokinetic analysis was based on a model-independent approach. Probenecid did not significantly affect the disposition of ceftriaxone in this study, thus suggesting that nonrenal excretion of ceftriaxone is not inhibited by probenecid.

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.

Micromethod for determination of ceftriaxone in plasma and urine by high-performance liquid chromatography

A sensitive and rapid high-performance liquid chromatographic method for the determination of ceftriaxone in human plasma and urine is described. A C18 reversed phase column is used; the mobile phase comprises water-methanol-triethylamine (750:250:4v/v/v) adjusted to pH 3 with orthophosphoric acid. Quantitation is performed at 270 nm with cefazolin as the internal standard. This method involves precipitation of proteins from fluids with acetonitrile followed by extraction of endogenous compounds with chloroform and injection of the upper aqueous phase on to the chromatograph. Relative standard deviations for between-day and within-day assays are 6.2%. The detection limit is 0.5 microg(-1) in plasma and urine. Studies of drug stability during sample storage, sample pretreatment and chromatography showed no degradation of ceftriaxone or of the internal standard. The method is convenient for clinical monitoring and for pharmacokinetic studies.

Influence of protein binding and severity of illness on renal elimination of four cephalosporin drugs in intensive-care patients

A pharmacokinetic study after a single dose of ceftriaxone, cefoxitin, cefuroxime and ceftazidime was performed to investigate the influence of protein binding and severity of disease on the renal elimination. In intensive-care patients drug-protein binding was substantially less compared to that in volunteers and patients with less complicated diseases. This did not result in increased elimination but, due to increased apparent volumes of distribution, prolonged half-life times were observed. Consequently, in patients with complicated disease states a dosage regimen should be based on pharmacokinetic studies performed in a similar patient group.

Pharmacokinetics of intravenous and intraperitoneal ceftriaxone in chronic ambulatory peritoneal dialysis

The kinetics of ceftriaxone was investigated in 8 patients without infection, who were receiving continuous ambulatory peritoneal dialysis (CAPD). Ceftriaxone 1 g was injected i.v. and 1 g was given intraperitoneally in the CAPD fluid during a 4-h dwell time. Ceftriaxone was assayed by HPLC. After intravenous administration, the kinetic parameters of ceftriaxone were: plasma t1/2, 12.3 h, total plasma clearance, 14.0 ml/min, volume of distribution at steady state 0.18 l/kg, and peritoneal clearance 0.59 ml/min. Over 72 hours only 5.5% of the dose was eliminated by the peritoneal route. After intraperitoneal administration, ceftriaxone rapidly appeared in serum; the absorption t1/2 was 1.1 h and the mean peak concentration was 38.8 micrograms/ml. The absorption of ceftriaxone from the peritoneal space was 39%. A single 1.0 g IP dose led to serum and dialysate concentrations of ceftriaxone above the minimum inhibitory concentration for susceptible pathogens for 24 hours.

Ceftriaxone pharmacokinetics during peritoneal dialysis

The purpose of this study was to investigate the pharmacokinetics of intraperitoneally (IP) administered ceftriaxone (CRO) in patients maintained on chronic peritoneal dialysis. A single 2 g dose of CRO was administered IP to six adult patients who did not have peritonitis at the time of study. After a 5 hour dwell, the peritoneal fluid was exchanged with CRO-free fluid. Exchanges were carried out every 4 to 8 h, over a 24- to 28-h period. The peak total plasma CRO concentration was 104 micrograms/ml. An average of 74.1% of the IP dose of CRO was absorbed. Plasma protein binding was nonlinear; mean free fraction ranged from 12.8 to 17.9% at low and high concentrations. Dialysate concentrations at the end of subsequent exchanges ranged from means of 19.9 to 2.9 micrograms/ml. Total CRO clearance from plasma was 10.1 ml X kg-1 X h-1 and the mean terminal t 1/2 was 12.7 h. Dialytic clearance averaged 0.69 ml X kg-1 X h-1, only 6.9% of total clearance. A model which incorporates known characteristics of CRO binding and distribution in anuric patients was used to simulate plasma and peritoneal concentrations of CRO during multiple dose IP drug administration.

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.

Drug therapy in patients undergoing peritoneal dialysis. Clinical pharmacokinetic considerations

Peritoneal dialysis has become an accepted treatment modality for end-stage renal disease. The introduction of continuous ambulatory peritoneal dialysis (CAPD) has further popularised this technique. The need for adjustment of drug dosage in patients with endstage renal disease and the need for supplemental dosages following haemodialysis are well recognised. Little documentation exists concerning the need for supplemental drug dosage in patients on peritoneal dialysis. Knowledge of the influence of peritoneal dialysis on the elimination of specific drugs is essential to the rational design of dosage regimens in patients undergoing this dialysis technique. This review addresses the clinical pharmacokinetic aspects of drug therapy in patients undergoing peritoneal dialysis and considers: the efficiency of the peritoneal membrane as a dialysing membrane; the effects of peritoneal dialysis on the pharmacokinetics of drugs; the pharmacokinetic models and estimation methods for peritoneal dialysis clearance and the effects of peritoneal dialysis on drug elimination; the influence of the pharmacokinetic parameters of drugs on drug dialysability; and the application of pharmacokinetic principles to the adjustment of drug dosage regimens in peritoneal dialysis patients. Data on drugs which have been studied in peritoneal dialysis are tabulated with inclusion of pharmacokinetic and dialysability information.

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.

[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)

The cephalosporin antibiotic agents--III. Third-generation cephalosporins

The third-“generation” cephalosporin antibiotics (Table 1) represent a class of agents with an expanded gram-negative spectrum of activity beyond that of the first- and second-“generation” cephalosporins. Greater stability to beta-lactamases produced by gram-negative organisms confers to these agents a greater bactericidal action against the Enterobacteriaceae. Large bacterial inocula (105/ml) in vitro significantly increase the minimum inhibitory and bactericidal concentrations (MIC and MBC) explaining treatment failures with these agents in infections associated with large numbers of organisms. The pharmacokinetic features of some of the agents allow prolongation of dosing intervals, and enhanced tissue penetration amplifies their clinical utility in infections distant from the bloodstream (eg, meningitis).

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.