Cefotaxime. A reappraisal of its antibacterial activity and pharmacokinetic properties, and a review of its therapeutic efficacy when administered twice daily for the treatment of mild to moderate infections

Population pharmacokinetics of cefotaxime in intensive care patients

PURPOSE

To characterise the pharmacokinetics and associated variability of cefotaxime in adult intensive care unit (ICU) patients and to assess the impact of patient covariates.

METHODS

This work was based on data from cefotaxime-treated patients included in the ACCIS (Antibiotic Concentrations in Critical Ill ICU Patients in Sweden) study. Clinical data from 51 patients at seven different ICUs in Sweden, given cefotaxime (1000-3000 mg given 2-6 times daily), were collected from the first day of treatment for up to three consecutive days. In total, 263 cefotaxime samples were included in the population pharmacokinetic analysis.

RESULTS

A two-compartment model with linear elimination, proportional residual error and inter-individual variability (IIV) on clearance and central volume of distribution best described the data. The typical individual was 64 years, with body weight at ICU admission of 92 kg and estimated creatinine clearance of 94 mL/min. The resulting typical value of clearance was 11.1 L/h, central volume of distribution 5.1 L, peripheral volume of distribution 18.2 L and inter-compartmental clearance 14.5 L/h. The estimated creatinine clearance proved to be a significant covariate on clearance (p < 0.001), reducing IIV from 68 to 49%.

CONCLUSION

A population pharmacokinetic model was developed to describe cefotaxime pharmacokinetics and associated variability in adult ICU patients. The estimated creatinine clearance partly explained the IIV in cefotaxime clearance. However, the remaining unexplained IIV is high and suggests a need for dose individualisation using therapeutic drug monitoring where the developed model, after evaluation of predictive performance, may provide support.

Validation of an HPLC method for estimation of cefotaxime from dried blood spot: alternative to plasma-based PK evaluation in neonates

Aim: Pharmacokinetic evaluation of cefotaxime in neonates is currently a challenge due to the large volume requirement of blood for its analysis by existing methods. A dried blood spot (DBS) based method is the best alternative. Materials & methods: We validated an HPLC method for estimation of cefotaxime from DBS and plasma. Extraction employed a simple procedure using acetonitrile and buffer. Selective separation of cefotaxime was achieved on a C8 column using gradient programming. Results & conclusion: The linearity of the method ranged from 2 to 200 μg/ml with acceptable precision and accuracy for both plasma and DBS. Hematocrit was not affecting the assay accuracy. A strong correlation and interchangeability observed with the plasma method proves its clinical validity for application to PK evaluations.

Complicated Intra-Abdominal Infections: The Old Antimicrobials and the New Players

Complicated intra-abdominal infections (cIAIs) are an important cause of morbidity and mortality worldwide. They are diagnosed when the initial abdominal organ infection has spread into the peritoneal space. Successful treatment relies on adequate source control and appropriate empiric antimicrobial therapy. Inappropriate antimicrobial therapy may result in poor patient outcomes and increases in healthcare costs. Current guidelines recommend several single and combination antimicrobial regimens; however, empiric antimicrobial treatment has been complicated by the increasing rates of resistant organisms, especially the extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae. Additionally, the overuse of carbapenems to combat these resistant pathogens has contributed to the rise of carbapenemase-producing microorganisms, especially Klebsiella pneumoniae. This increasing resistance has prompted the development of novel antimicrobials like ceftazidime-avibactam and ceftolozane-tazobactam, whose activity extends to ESBL-producing microorganisms. Furthermore, the optimal duration of antimicrobial therapy is still unknown, and further research is necessary to find a definitive answer. This review will focus on antimicrobial therapies recommended by the current guidelines, the individual properties of these agents, appropriate duration of therapy, recent clinical trials, and place in therapy of the antimicrobial agents recently approved for the treatment of cIAIs.

Pharmacokinetic modelling of cefotaxime and desacetylcefotaxime--a population study in 25 elderly patients

OBJECTIVE

To develop a pharmacostatistical model to simultaneously characterise the pharmacokinetics of cefotaxime and its main metabolite, desacetylcefotaxime, in elderly patients.

METHODS

Cefotaxime, 1 g, was infused three times daily to 25 elderly patients, 66-93 years old. Cefotaxime and desacetylcefotaxime plasma concentrations (289 and 304 samples, respectively), along with demographic and physiological characteristics, were analysed using a population approach.

RESULTS

Cefotaxime pharmacokinetics was best described by a two-compartment open model in which desacetylcefotaxime was produced from the central compartment. The final parameter estimates were derived from simultaneous fit of parent/metabolite data. Cefotaxime clearance, mean 5.5 l/h, was positively influenced by body weight and serum protein concentration and negatively influenced by serum creatinine and age. In contrast, desacetylcefotaxime elimination was only decreased by age. The mean terminal half-lives of cefotaxime and desacetylcefotaxime were 1.7 h and 2.6 h, respectively. The stability and predictive performance of the final population pharmacokinetic model was assessed using 200 bootstrap samples of the original data.

CONCLUSION

Cefotaxime and desacetylcefotaxime elimination decreased with increasing age above 60 years. This decreased elimination was related to individual characteristics that are typically related to renal function.

Commonly used antibacterial and antifungal agents for hospitalised paediatric patients: implications for therapy with an emphasis on clinical pharmacokinetics

Due to normal growth and development, hospitalised paediatric patients with infection require unique consideration of immune function and drug disposition. Specifically, antibacterial and antifungal pharmacokinetics are influenced by volume of distribution, drug binding and elimination, which are a reflection of changing extracellular fluid volume, quantity and quality of plasma proteins, and renal and hepatic function. However, there is a paucity of data in paediatric patients addressing these issues and many empiric treatment practices are based on adult data. The penicillins and cephalosporins continue to be a mainstay of therapy because of their broad spectrum of activity, clinical efficacy and favourable tolerability profile. These antibacterials rapidly reach peak serum concentrations and readily diffuse into body tissues. Good penetration into the cerebrospinal fluid (CSF) has made the third-generation cephalosporins the agents of choice for the treatment of bacterial meningitis. These drugs are excreted primarily by the kidney. The carbapenems are broad-spectrum beta-lactam antibacterials which can potentially replace combination regimens. Vancomycin is a glycopeptide antibacterial with gram-positive activity useful for the treatment of resistant infections, or for those patients allergic to penicillins and cephalosporins. Volume of distribution is affected by age, gender, and bodyweight. It diffuses well across serous membranes and inflamed meninges. Vancomycin is excreted by the kidneys and is not removed by dialysis. The aminoglycosides continue to serve a useful role in the treatment of gram-negative, enterococcal and mycobacterial infections. Their volume of distribution approximates extracellular space. These drugs are also excreted renally and are removed by haemodialysis. Passage across the blood-brain barrier is poor, even in the face of meningeal inflammation. Low pH found in abscess conditions impairs function. Toxicity needs to be considered. Macrolide antibacterials are frequently used in the treatment of respiratory infections. Parenteral erythromycin can cause phlebitis, which limits its use. Parenteral azithromycin is better tolerated but paediatric pharmacokinetic data are lacking. Clindamycin is frequently used when anaerobic infections are suspected. Good oral absorption makes it a good choice for step-down therapy in intra-abdominal and skeletal infections. The use of quinolones in paediatrics has been restricted and most information available is in cystic fibrosis patients. High oral bioavailability is also important for step-down therapy. Amphotericin B has been the cornerstone of antifungal treatment in hospitalised patients. Its metabolism is poorly understood. The half-life increases with time and can be as long as 15 days after prolonged therapy. Oral absorption is poor. The azole antifungals are being used increasingly. Fluconazole is well tolerated, with high bioavailability and good penetration into the CSF. Itraconazole has greater activity against aspergillus, blastomycosis, histoplasmosis and sporotrichosis, although it's pharmacological and toxicity profiles are not as favourable.

Brain Abscess

Optimal treatment of a brain abscess requires early clinical suspicion, and the diagnosis is usually made by identification of the abscess on contrast-enhanced computed tomography (CT) or magnetic resonance imaging (MRI). The immediate first step is to reduce the potentially life-threatening brain mass (abscess and surrounding cerebral edema) and secure the diagnosis with culture specimens. This is usually accomplished by reducing the increased intracranial pressure (ICP) through surgical aspiration with or without drainage of the abscess pus. The surgical procedure chosen depends on several factors, including the location and type of abscess, multiplicity, and the medical condition of the patient. In addition, dexamethasone and hyperventilation may be required if brain herniation is imminent. The dexamethasone dose should be reduced as soon as the ICP is reduced because steroid administration may retard abscess capsule formation and decrease antibiotic concentrations within the abscess cavity. Antibiotic therapy should be started as soon as the diagnosis is made. Penicillin G or third-generation cephalosporins plus metronidazole are commonly given to treat both anaerobic and aerobic bacteria. The initial choice of antibiotic will vary on the basis of the suspected source of the brain organisms, which is most often either contiguous spread from a sinus or mastoid infection or hematogenous spread from a pulmonary, gastrointestinal, cardiac, or dental infection. Isolation and determination of the antibiotic sensitivities of the organism from abscess pus allow definitive antibiotic therapy. Patients should be managed in an intensive care unit. Phenytoin is often given to prevent seizures, which could further elevate the ICP. The duration of antimicrobial treatment is 4 to 8 weeks, during which time the patient should be monitored clinically and with repeated neuroimaging studies to ensure abscess resolution.

The cephalosporins

The cephalosporins are a large group of related beta-lactam antimicrobial agents. Favorable attributes of the cephalosporins include low rates of toxicity, relatively broad spectrum of activity, and ease of administration. Various cephalosporins are effective for treatment of many conditions, including pneumonia, skin and soft tissue infections, bacteremia, and meningitis. Differences among the numerous cephalosporin antimicrobial agents are sometimes subtle; however, an understanding of these differences is essential for optimal use of these agents. As a result of widespread use of cephalosporins, bacterial resistance to these drugs is increasingly common. New, fourth-generation agents (such as cefepime) offer an alternative for the treatment of infections caused by some drug-resistant microorganisms.

Clinical and pharmacological evaluation of a modified cefotaxime bid regimen versus traditional tid in pediatric lower respiratory tract infections

It is generally accepted that the treatment of community-acquired pneumonia, either in adults or in pediatric patients, is mainly empirical. Thus, the treatment selection must fulfill both the epidemiological requirements, according to the most frequently described pathogens, and the pharmacological criteria to ensure adequate and prolonged drug concentrations at the infection site, to reach clinical efficacy. Cefotaxime has proven to be effective in this indication when traditionally administered three times daily and, more recently, twice daily, as a result of a re-evaluation of its pharmacokinetic/pharmacodynamic features. To gain further evidence using this updated dosing schedule, 258 pediatric patients with lower respiratory tract infections were treated with cefotaxime 100 mg/kg/day, administered as a twice daily or three times daily regimen. In the cefotaxime 50 mg/kg twice-daily group (n = 130), a complete resolution of clinical signs and symptoms were observed in 88.5% of patients. Similarly, in the cefotaxime 33.3 mg/kg group (n = 128), 93.6% of patients had a complete resolution of clinical signs and symptoms. Both drug schedules were well tolerated. Pharmacokinetic parameters determined for the two cefotaxime dosing schedules showed comparability. The serum half-life of desacetylcefotaxime was marginally longer than for cefotaxime in both dosage groups (1.64 and 1.36 h for desacetylcefotaxime versus 1.2 and 0.85 h for cefotaxime after 50 mg/kg or 33.3 mg/kg doses, respectively). Results from this study support the use of twice-daily cefotaxime administration for the treatment of lower respiratory tract infections in pediatric patients.