Pharmacokinetics of amoxycillin/clavulanic acid in serum and ascitic fluid in cirrhotic patients

Evolving epidemiology and antimicrobial resistance in spontaneous bacterial peritonitis: a two-year observational study

BACKGROUND

Current recommendations for empirical antimicrobial therapy in spontaneous bacterial peritonitis (SBP) are based on quite old trials. Since microbial epidemiology and the management of patients have changed, whether these recommendations are still appropriate must be confirmed.

METHODS

An observational study that exhaustively collected the clinical and biological data associated with positive ascitic fluid cultures was conducted in four French university hospitals in 2010-2011.

RESULTS

Two hundred and sixty-eight documented positive cultures were observed in 190 cirrhotic patients (median age 61.5 years, 58.5% Child score C). Of these, 57 were classified as confirmed SBP and 140 as confirmed bacterascites. The predominant flora was Gram-positive cocci, whatever the situation (SBP, bacterascites, nosocomial/health-care related or not). Enteroccocci (27.7% E. faecium) were isolated in 24% of the episodes, and in 48% from patients receiving quinolone prophylaxis. E. coli were susceptible to amoxicillin-clavulanate and to third-generation cephalosporins in 62.5% and 89.5% of cases, respectively. No single antibiotic allowed antimicrobial coverage of more than 60%. Only combinations such as amoxicillin + third-generation cephalosporin or cotrimoxazole allowed coverage close to 75-80% in non-nosocomial episodes. Combinations based on broader spectrum antibiotics should be considered for empirical therapy of nosocomial infections.

CONCLUSIONS

Our study confirmed the changing spectrum of pathogens in SBP and bacterascites, and the need for more complex antibiotic strategies than those previously recommended. Our findings also underline the need for new clinical trials conducted in the current epidemiological context.

New formulations of amoxicillin/clavulanic acid: a pharmacokinetic and pharmacodynamic review

The pharmacokinetic properties of amoxicillin and clavulanic acid when used alone or in combination are extensively reviewed and discussed in this article. The reported data support a nonlinear absorption process for amoxicillin. Saturable transport mechanisms, limited solubility and the existence of an absorption window are possibly involved in the gastrointestinal absorption of this antibacterial, all leading to a decrease in the peak plasma concentration (Cmax)/dose ratio, a prolongation of the time to reach Cmax, and broad variability for high doses of amoxicillin. Data available in the literature also suggest a possible interaction between amoxicillin and clavulanic acid that might decrease the absolute bioavailability of clavulanic acid. In the present review the intrinsic pharmacodynamics of each drug, together with the synergism produced by the amoxicillin/clavulanic acid association, are also reviewed and analysed. Not only beta-lactamase-producing strains, but also Streptococcus pneumoniae strains, seem to be more efficiently eradicated by the association of amoxicillin and clavulanic acid, and a relevant post-antibacterial effect and post-beta-lactamase inhibitor effect are likely to operate when amoxicillin is administered together with clavulanic acid. The principles of pharmacokinetic/pharmacodynamic analysis applied to amoxicillin are reviewed, with special emphasis being placed on the results obtained from in vitro studies and animal models regarding the new pharmacokinetically enhanced formulation. Theoretical considerations concerning the efficacy of this formulation provided by the application of pharmacokinetic/pharmacodynamic analysis to the scarce pharmacokinetic data available are also included. The broad pharmacokinetic variability of both amoxicillin and clavulanic acid, particularly when administered together and at high doses of amoxicillin, is highlighted and the interest in considering this aspect to improve predictions based on pharmacokinetic/pharmacodynamic analyses for the new formulations is indicated. Methodological recommendations such as the Monte Carlo simulation are proposed in order to obtain more realistic predictions in clinical practice.

Antibiotic pharmacokinetic and pharmacodynamic considerations in critical illness

BACKGROUND

Many factors over which there may be little control may influence the response of a patient to therapy. However, therapy with antibiotics can be readily optimised.

DISCUSSION

Concentration-dependent agents such as aminoglycosides appear effective and to entail fewer side effects when given in large, infrequent doses. There is also evidence that time-dependent antibiotics often fail to reach adequate concentrations throughout the treatment period. To date no randomised controlled prospective trial has demonstrated improvement in clinical outcome following infusion rather than intermittent boluses of time-dependent antibiotics. Critical illness alters antibiotic pharmacokinetics principally through increases in volume of distribution. Other than glycopeptides and aminoglycosides, antibiotic blood concentrations are rarely monitored and therefore adequate concentrations can only be inferred from clinical response.

CONCLUSIONS

Failure to respond within the first few days of empirical treatment may be due to antibiotic resistance or inadequate doses. Therefore the same rigor should be applied to achieving adequate antibiotic concentrations as is applied to inotropes, which are titrated to achieve predetermined physiological targets.

Amoxicillin-clavulanic acid versus cefotaxime in the therapy of bacterial infections in cirrhotic patients

BACKGROUND/AIM

Cefotaxime is considered the first-choice antibiotic for empirical treatment in cirrhotic patients developing bacterial infections. It has been suggested that amoxicillin-clavulanic acid could be an alternative to cefotaxime, particularly in patients developing bacterial infections while on prophylactic norfloxacin. The aim of the present study was to compare amoxicillin-clavulanic acid with cefotaxime in the treatment of bacterial infections in cirrhosis.

METHODS

Ninety-six hospitalized cirrhotic patients with suspicion of bacterial infection were prospectively included and randomized into two groups: one group (n=48) received amoxicillin-clavulanic acid, first intravenously 1 g-0.2 g every 8 h, and then orally 500 mg-125 mg every 8 h, and the other group (n=48) received intravenous cefotaxime 1 g every 6 h. Patients were stratified for previous prophylaxis with norfloxacin and ascitic fluid infection.

RESULTS

Sixteen patients were excluded from the analysis because bacterial infection was not demonstrated or because of secondary peritonitis. Therefore, 38 patients from the amoxicillin-clavulanic acid group and 42 from the cefotaxime group were finally analyzed. There were 24 ascitic fluid infections in each group. Infection resolution (86.8% vs 88%, 95% CI: -0.15 to 0.13, p NS), spontaneous bacterial peritonitis resolution (87.5% vs 83.3%, 95% CI: -0.15 to 0.24, p NS), duration of treatment, incidence of complications, time of hospitalization and hospital mortality were similar in both groups. Considering patients on prophylactic norfloxacin, infection resolution was also similar (100% vs 83.3%, 95% CI: -0.04 to 0.37, p NS). No adverse events were observed in either of the two groups. The cost of antibiotics was statistically lower in the amoxicillin-clavulanic acid group (p<0.001).

CONCLUSIONS

Amoxicillin-clavulanic acid is as effective as cefotaxime in the treatment of bacterial infections in cirrhotic patients, but is less expensive and can be administered orally. These results suggest that amoxicillin-clavulanic acid is an effective alternative to cefotaxime for the empirical treatment of bacterial infections in cirrhosis.

Amoxicillin-clavulanic acid therapy of spontaneous bacterial peritonitis: a prospective study of twenty-seven cases in cirrhotic patients

Spontaneous bacterial peritonitis in cirrhosis is a serious complication that demands urgent attention. We report here a prospective study of the treatment of 27 episodes of spontaneous bacterial peritonitis in 22 cirrhotic patients with amoxicillin and clavulanic acid. The infection of ascitic fluid was diagnosed by a positive culture plus an ascitic neutrophil count exceeding 75/microliters, or by an ascitic neutrophil count exceeding 500/microliters. The infection was treated with 1 gm amoxicillin and 0.2 gm clavulanic acid every 6 hr for 14 days. In 17 cases (63%), bacteria were isolated from the ascitic fluid. All the bacteria isolated were sensitive to amoxicillin and clavulanic acid, whereas in five cases they were resistant to amoxicillin alone (Escherichia coli in two cases, Klebsiella pneumoniae in two cases and Bacteroides fragilis in one case). Cure of the infection was achieved in 23 episodes (85%) after 14 days' treatment; 17 patients (63%) were able to leave the hospital. Fourteen of 20 patients (70%) treated for the first episode of infection died within 1 yr: eight from infection, two from gastrointestinal hemorrhage, one from infection and hemorrhage and three from tumors. One patient who had repeated infections underwent liver transplantation and has not had any infectious complications 1.5 yr after surgery. Amoxicillin and clavulanic acid may be an effective first-line therapy for ascitic fluid infection in cirrhosis. Nevertheless, the 1-yr prognosis continues to be grave and the severity of the underlying liver disease remains the most important determinant for survival.