Amoxycillin clavulanate: an assessment after 15 years of clinical application

Pharmacodynamics of imipenem in combination with β-lactamase inhibitor MK7655 in a murine thigh model

MK7655 is a newly developed beta-lactamase inhibitor of class A and class C carbapenemases. Pharmacokinetics (PK) of imipenem-cilastatin (IMP/C) and MK7655 were determined for intraperitoneal doses of 4 mg/kg to 128 mg/kg of body weight. MIC and pharmacodynamics (PD) studies of MK7655 were performed against several beta-lactamase producing Pseudomonas aeruginosa and Klebsiella pneumoniae strains to determine its effect in vitro and in vivo. Neutropenic mice were infected in each thigh 2 h before treatment with an inoculum of approximately 5×10(6) CFU. They were treated with IMP/C alone (every 2 hours [q2h], various doses) or in combination with MK7655 in either a dose fractionation study or q2h for 24 h and sacrificed for CFU determinations. IMP/MK7655 decreased MICs regarding IMP MIC. The PK profiles of IMP/C and MK7655 were linear over the dosing range studied and comparable with volumes of distribution (V) of 0.434 and 0.544 liter/kg and half-lives (t1/2) of 0.24 and 0.25 h, respectively. Protein binding of MK7655 was 20%. A sigmoidal maximum effect (Emax) model was fit to the PK/PD index responses. The effect of the inhibitor was not related to the maximum concentration of drug in serum (Cmax)/MIC, and model fits for T>MIC and area under the concentration-time curve (AUC)/MIC were comparable (R2 of 0.7 and 0.75), but there appeared to be no significant relationship of effect with dose frequency. Escalating doses of MK7655 and IMP/C showed that the AUC of MK7655 required for a static effect was dependent on the dose of IMP/C and the MIC of the strain, with a mean area under the concentration-time curve for the free, unbound fraction of the drug (fAUC) of 26.0 mg · h/liter. MK7655 shows significant activity in vivo and results in efficacy of IMP/C in otherwise resistant strains. The exposure-response relationships found can serve as a basis for establishing dosing regimens in humans.

Oral antibiotics for fever in low-risk neutropenic patients with cancer: a double-blind, randomized, multicenter trial comparing single daily moxifloxacin with twice daily ciprofloxacin plus amoxicillin/clavulanic acid combination therapy--EORTC infectious diseases group trial XV

PURPOSE

This double-blind, multicenter trial compared the efficacy and safety of a single daily oral dose of moxifloxacin with oral combination therapy in low-risk febrile neutropenic patients with cancer.

PATIENTS AND METHODS

Inclusion criteria were cancer, febrile neutropenia, low risk of complications as predicted by a Multinational Association for Supportive Care in Cancer (MASCC) score > 20, ability to swallow, and ≤ one single intravenous dose of empiric antibiotic therapy before study drug treatment initiation. Early discharge was encouraged when a set of predefined criteria was met. Patients received either moxifloxacin (400 mg once daily) monotherapy or oral ciprofloxacin (750 mg twice daily) plus amoxicillin/clavulanic acid (1,000 mg twice daily). The trial was designed to show equivalence of the two drug regimens in terms of therapy success, defined as defervescence and improvement in clinical status during study drug treatment (< 10% difference).

RESULTS

Among the 333 patients evaluated in an intention-to-treat analysis, therapy success was observed in 80% of the patients administered moxifloxacin and in 82% of the patients administered combination therapy (95% CI for the difference, -10% to 8%, consistent with equivalence). Minor differences in tolerability, safety, and reasons for failure were observed. More than 50% of the patients in the two arms were discharged on protocol therapy, with 5% readmissions among those in either arm. Survival was similar (99%) in both arms.

CONCLUSION

Monotherapy with once daily oral moxifloxacin is efficacious and safe in low-risk febrile neutropenic patients identified with the help of the MASCC scoring system, discharged early, and observed as outpatients.

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.

Antimicrobial therapy in Dermatology

The extensive and sometimes indiscriminate use of antibiotics sometimes without strict indications has led to increases in both bacterial resistance and sensitization of patients. Systemic antibiotics in skin infections are indicated when a severe local infection occurs which spreads into the surrounding tissue or when there are signs of systemic infection. There are special indications in patients with peripheral arterial occlusive disease,diabetes or immunosuppression. Topical use of antibiotics should be abandoned and replaced by antiseptics. The beta-lactam antibiotics are the antibiotics of first choice for many skin infections. They are usually effective, have a well-defined profile of adverse events and most are affordable. Penicillin G or V are the first line treatment for erysipelas. Infections with Staphylococcus aureus are usually treated with isoxazolyl penicillins or second generation cephalosporins. In mixed infections in patients with diabetes or peripheral arterial occlusive disease,the treatment of choice is metronidazole plus beta-lactam-/beta-lactamase inhibitor antibiotics, but quinolones or second generation cephalosporins can also be used, once again with metronidazole. The aim of this review is to define the indications for antibiotics in dermatology, to highlight their modes of action and adverse effects and to make suggestions for rational antibiotic therapy in cutaneous infections frequently encountered in the practice of dermatology.

Proof of concept: performance testing in models

Pharmacokinetic (PK) and pharmacodynamic (PD) principles that predict antimicrobial efficacy can be used to set targets for antimicrobial design and optimisation. Although current formulations of amoxicillin and amoxicillin/clavulanate have retained their efficacy against many, but not all, penicillin-nonsusceptible Streptococcus pneumoniae, additional coverage is required to address the growing problem of drug-resistant strains. Accordingly, two new oral formulations of amoxicillin/clavulanate, a paediatric formulation at 90/6.4 mg/kg/day and a pharmacokinetically enhanced formulation at 2000/125 mg twice daily for adults, were designed using PK/PD principles. These principles indicate that for amoxicillin and amoxicillin/clavulanate, a time above MIC of 35-40% of the dosing interval is predictive of high bacterial efficacy. In line with PK/PD predictions, simulation of human pharmacokinetics in in-vitro kinetic models and in a rat model of pneumonia, amoxicillin/clavulanate 2000/125 mg twice daily was highly effective against S. pneumoniae strains with amoxicillin MICs of 4 or 8 mg/L. Against strains with amoxicillin MICs of 4 mg/L, amoxicillin/clavulanate 2000/125 mg twice daily was significantly more effective than the conventional 875/125 mg twice daily formulation, azithromycin and levofloxacin, even though all levofloxacin MICs were < or = 1 mg/L. Following infection with S. pneumoniae strains with amoxicillin MICs of 8 mg/L, the amoxicillin/clavulanate 2000/125 mg twice daily formulation was more effective than the conventional amoxicillin/clavulanate formulations of 875/125 mg twice daily and three times daily and 1000/125 mg three times daily, and had similar or better efficacy than azithromycin and levofloxacin, depending on the strain. These data indicate the potential benefit of therapy with amoxicillin/clavulanate 2000/125 mg twice daily compared with conventional formulations and other marketed antimicrobials in the treatment of respiratory tract infection.

In vitro activity of gemifloxacin and contemporary oral antimicrobial agents against 27,247 Gram-positive and Gram-negative aerobic isolates: a global surveillance study

This study was a multi-centre, multi-country surveillance of 27247 Gram-positive and Gram-negative isolates collected from 131 study centres in 44 countries from 1997 to 2000. MICs of gemifloxacin were compared with penicillin, amoxicillin-clavulanic acid, cefuroxime, azithromycin, clarithromycin, trimethoprim-sulphamethoxazole, ciprofloxacin, grepafloxacin and levofloxacin by broth microdilution. Penicillin resistance in Streptococcus pneumoniae was extremely high in the Middle East (65.6%), Africa (64.0%) and Asia (60.4%) and lower in North America (40.3%), Europe (36.9%) and the South Pacific (31.8%). Macrolide resistance in S. pneumoniae was highest in Asia (51.7%) but varied widely between laboratories in Europe (26.0%), North America (21.6%), the Middle East (13.7%), the South Pacific (10.6%) and Africa (10.0%). All the study quinolones were highly active against penicillin-resistant and macrolide-resistant S. pneumoniae. Overall, gemifloxacin had the lowest MIC(90) at 0.06 mg/l with MICs 4-64-fold lower than ciprofloxacin, levofloxacin and grepafloxacin against S. pneumoniae. Gemifloxacin MICs were more potent than grepafloxacin > levoflaxacin > ciproflaxin against the Gram-positive aerobes and shared comparable Gram-negative activity with ciprofloxacin and levofloxacin.

Current Issues in the Management of Bacterial Respiratory Tract Disease: The Challenge of Antibacterial Resistance

The worldwide burden of respiratory tract disease is enormous. Resistance to penicillins, macrolides, and cephalosporins is now detected among the leading bacterial pathogens that cause respiratory tract infections (RTIs)-Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. The increasing role of atypical/intracellular pathogens (eg, Chlamydia pneumoniae, Mycoplasma pneumoniae, Legionella pneumophila) in RTIs, as well as their increase in antibiotic resistance prevalence, continues to be of great concern. More recently introduced treatment options for RTIs include the newer respiratory fluoroquinolones, along with the macrolides and azalides. Although these agents demonstrate good activity against common respiratory pathogens, reduced susceptibility to these agents has been reported. The ketolides are recently developed antibacterial agents with targeted-spectrum activity against common respiratory tract pathogens, including atypical/intracellular pathogens, and a low potential for inducing resistance. These promising new drugs have shown in vitro and in vivo efficacy in the treatment of community-acquired RTIs, such as community-acquired pneumonia, acute exacerbations of chronic bronchitis, and acute bacterial maxillary sinusitis.

Comparative in vitro surveillance of amoxicillin-clavulanic acid and four oral comparators against 21232 clinical isolates from europe

The present study was conducted to determine the in vitro activity of amoxicillin-clavulanic acid compared to that of four newer antimicrobial agents (ampicillin, azithromycin, cefuroxime and trimethoprim-sulfamethoxazole). All of the agents were tested against 21232 recent clinical isolates encompassing 37 species submitted from 16 European countries between 1997 and 1999. After 20 years of clinical use, amoxicillin-clavulanic acid continues to retain much of its initial activity against targeted gram-positive organisms, selected gram-negative organisms and major respiratory pathogens.

Outcome of treatment of respiratory tract infections due to Streptococcus pneumoniae, including drug-resistant strains, with pharmacokinetically enhanced amoxycillin/clavulanate

The efficacy of a new pharmacokinetically enhanced formulation of amoxycillin/clavulanate (AMX/CA) 2000/125 mg, twice daily, designed to provide adequate levels of amoxycillin over the 12-h dosing interval to eradicate penicillin-resistant Streptococcus pneumoniae (PRSP) with amoxycillin (+/-clavulanic acid) MICs of </=4 mg/l, was evaluated in patients with respiratory infections caused by S. pneumoniae, including PRSP (penicillin MICs 2-16 mg/l). Data from nine clinical studies were combined (total intent-to-treat N=5531). Six randomized, double-blind studies used levofloxacin 500 mg od in acute bacterial sinusitis (ABS), levofloxacin 500 mg od in acute exacerbations of chronic bronchitis (AECB), clarithromycin 500 mg bid in AECB, AMX/CA 875/125 mg bid and tid in community-acquired pneumonia (CAP) and AMX/CA 1000/125 mg tid in CAP as comparators. The three remaining studies (two in ABS and one in CAP) were non-comparative. In the AMX/CA 2000/125 mg bid-treated patients evaluable at follow-up (Day 14-39), outcome was successful in 60/64 (93.7%) patients with S. pneumoniae infections in the comparative studies and 348/363 (95.9%) in the non-comparative studies, including 95.6% of all patients and 95.2% of patients whose isolates had AMX/CA MICs of >/=4 mg/l. In the pooled comparator group, the success rate at follow-up was 86.5% (45/52). For PRSP (AMX/CA MICs of 0.5-8 mg/l), the overall success rate was 98.2% (55/56) at follow-up for AMX/CA 2000/125 mg and 50.0% (2/4) for comparators. AMX/CA 2000/125 mg shows efficacy comparable to that of the comparators evaluated against S. pneumoniae infections. Due to its favorable pharmacokinetic/pharmacodynamic profile and promising clinical success, the new AMX/CA 2000/125 mg formulation should be considered for the empirical treatment of respiratory tract infections in regions with a high prevalence of antimicrobial-resistant S. pneumoniae and in patients at high risk of antimicrobial-resistant S. pneumoniae infection as this formulation covers many PRSP that are non-susceptible to amoxycillin (+/-clavulanic acid) (MICs of >/=4 mg/l) as well as common beta-lactamase-producing respiratory pathogens.

In vitro susceptibility of Staphylococcus aureus towards amoxycillin-clavulanic acid, penicillin-clavulanic acid, dicloxacillin and cefuroxime

Sixty-three Staphylococcus aureus isolates with a wide distribution in quantitative beta-lactamase production were tested in vitro against amoxycillin and penicillin in combination with clavulanic acid to establish the influence of total amount of beta-lactamase present on the ability of clavulanic acid to protect against beta-lactamase degradation. The beta-lactamase stability of cefuroxime and dicloxacillin was also evaluated. MIC was determined by agar dilution using Mueller-Hinton agar with both a conventional as well as a 100 times higher inoculum. The strains were tested both with and without induction of the beta-lactamase production. Clavulanic acid was highly effective in protecting against beta-lactamase degradation of both penicillin and amoxycillin. Even when using a high inoculum of strains with induced beta-lactamase production, all strains had MICs below the NCCLS breakpoint of 4/2 mg/l for amoxycillin-clavulanic acid. Both cefuroxime and dicloxacillin were highly stable against staphylococcal beta-lactamase degradation. This study encourages further in vivo evaluation of amoxycillin-clavulanic acid for severe staphylococcal infections.

Gemifloxacin versus amoxicillin/clavulanate in the treatment of acute exacerbations of chronic bronchitis. The 070 Clinical Study group

Six hundred patients were evaluated in this randomized, double-blind, double-dummy, multicenter, parallel-group study comparing the efficacy and safety of gemifloxacin (320 mg once-daily for 5 days) and amoxicillin/clavulanate (500/125 mg three-times daily for 7 days) for the treatment of acute exacerbations of chronic bronchitis (AECB). Of note, more than 90% of study participants had stage 2 disease at study entry. The two drugs were found to be equally effective, with clinical success rates of 93.6% for gemifloxacin and 93.2% on amoxicillin/clavulanate (95% CI -3.9 to 4.6). Bacteriological success rates favored gemifloxacin (90.9% compared with 79.5% for amoxicillin/clavulanate; 95% CI -3.3 to 26.0); however, this difference was not statistically significant. Gemifloxacin and amoxicillin/clavulanate were both well tolerated. In summary, gemifloxacin was found to be well tolerated and effective for the treatment of AECB, suggesting it is well suited for empirical treatment of this common respiratory condition in the current clinical environment.

Sinus tissue pharmacokinetics after oral administration of amoxicillin/clavulanic acid

OBJECTIVES

The in vitro synergy of the amoxicillin/clavulanic acid combination has not always translated in vivo into clinical superiority compared with amoxicillin alone. Specifically, conflicting reports have disputed the superiority of the combination in the treatment of both acute otitis media and acute sinusitis. One possible reason for this may have to do with inadequate target tissue pharmacokinetics. To explore this possibility in the sinuses, we undertook the present investigation.

STUDY DESIGN

A randomized, open, single-dose, sinus tissue pharmacokinetic study with oral amoxicillin/clavulanic acid.

METHODS

Twenty-three adult patients with chronic rhinosinusitis who had been selected for surgery were randomly allocated to receive a tablet of 875/125 mg amoxicillin/clavulanate 2 to 4 hours before surgery began. During the operation tissue samples were collected at specific sinonasal sites for determination of both amoxicillin and clavulanic acid concentration levels.

RESULTS

Amoxicillin displayed adequate tissue levels throughout the sinuses, high enough to cover common susceptible pathogens. However, the presence of clavulanate was detected in only half of the sinonasal tissue samples.

CONCLUSIONS

The kinetics of oral clavulanic acid apparently fails to provide a widespread anti-beta-lactamase activity capable of enhancing the activity of amoxicillin in all parts of the sinuses. Despite this, amoxicillin/clavulanic acid maintains a central role in the treatment of acute rhinosinusitis, because amoxicillin is still the most effective oral beta-lactam against Streptococcus pneumoniae, a particularly virulent and increasingly resistant upper respiratory tract pathogen. Also, as our data show, a concomitant anti-beta-lactamase activity can be expected to occur, although in an unpredictable fashion.

Prospective, randomised, double blind trial of prophylaxis with single dose of co-amoxiclav before percutaneous endoscopic gastrostomy

OBJECTIVE

To determine the efficacy of antibacterial prophylaxis in preventing infectious complications after percutaneous endoscopic gastrostomy.

DESIGN

Prospective, randomised, placebo controlled, double blind, multicentre study.

SETTING

Departments of internal medicine at six German hospitals.

SUBJECTS

Of 106 randomised adult patients with dysphagia, 97 received study medication, and 84 completed the study. The median age of the patients was 65 years. Most had dysphagia due to malignant disease (65%), and many (76%) had serious comorbidity.

INTERVENTIONS

A single intravenous 2.2 g dose of co-amoxiclav or identical appearing saline was given 30 min before percutaneous endoscopic gastrostomy performed by the thread pull method.

MAIN OUTCOME MEASURES

Occurrence of peristomal wound infections and other infections within one week after percutaneous endoscopic gastrostomy.

RESULTS

The incidence of peristomal and other infections within one week after percutaneous endoscopic gastrostomy was significantly reduced in the antibiotic group (8/41 (20%) v 28/43 (65%), P<0.001). Similar results were obtained in an intention to treat analysis. Several peristomal wound infections were of minor clinical significance. After wound infections that required no or only local treatment were excluded from the analysis, antibiotic prophylaxis remained highly effective in reducing clinically important wound infections (1/41 (2%) v 11/43 (26%), P<0.01) and non-wound infections (2 (5%) v 9 (21%), P<0.05).

CONCLUSIONS

Antibiotic prophylaxis with a single dose of co-amoxiclav significantly reduces the risk of infectious complications after percutaneous endoscopic gastrostomy and should be recommended.

Oral versus intravenous empirical antimicrobial therapy for fever in patients with granulocytopenia who are receiving cancer chemotherapy. International Antimicrobial Therapy Cooperative Group of the European Organization for Research and Treatment of Cancer

BACKGROUND

Intravenously administered antimicrobial agents have been the standard choice for the empirical management of fever in patients with cancer and granulocytopenia. If orally administered empirical therapy is as effective as intravenous therapy, it would offer advantages such as improved quality of life and lower cost.

METHODS

In a prospective, open-label, multicenter trial, we randomly assigned febrile patients with cancer who had granulocytopenia that was expected to resolve within 10 days to receive empirical therapy with either oral ciprofloxacin (750 mg twice daily) plus amoxicillin-clavulanate (625 mg three times daily) or standard daily doses of intravenous ceftriaxone plus amikacin. All patients were hospitalized until their fever resolved. The primary objective of the study was to determine whether there was equivalence between the regimens, defined as an absolute difference in the rates of success of 10 percent or less.

RESULTS

Equivalence was demonstrated at the second interim analysis, and the trial was terminated after the enrollment of 353 patients. In the analysis of the 312 patients who were treated according to the protocol and who could be evaluated, treatment was successful in 86 percent of the patients in the oral-therapy group (95 percent confidence interval, 80 to 91 percent) and 84 percent of those in the intravenous-therapy group (95 percent confidence interval, 78 to 90 percent; P=0.02). The results were similar in the intention-to-treat analysis (80 percent and 77 percent, respectively; P=0.03), as were the duration of fever, the time to a change in the regimen, the reasons for such a change, the duration of therapy, and survival. The types of adverse events differed slightly between the groups but were similar in frequency.

CONCLUSIONS

In low-risk patients with cancer who have fever and granulocytopenia, oral therapy with ciprofloxacin plus amoxicillin-clavulanate is as effective as intravenous therapy.

Penetration of beta-lactamase inhibitors into the periplasm of gram-negative bacteria

The effectiveness of a beta-lactamase inhibitor/beta-lactam combination against Gram-negative pathogens depends on many interplaying factors, one of which is the penetration of the inhibitor across the outer membrane. In this work we have measured the relative penetrations of clavulanic acid, sulbactam, tazobactam and BRL 42715 into two strains of Escherichia coli producing TEM-1 beta-lactamase, two strains of Klebsiella pneumoniae producing either TEM-1 or K-1, and two strains of Enterobacter cloacae each producing a Class C beta-lactamase. It was shown that clavulanic acid penetrated the outer membranes of all these strains more readily than the other beta-lactamase inhibitors. For the strains of E. coli and K. pneumoniae clavulanic acid penetrated approximately 6 to 19 times more effectively than tazobactam, 2 to 9 times more effectively than sulbactam and 4 to 25 times more effectively than BRL 42715. The superior penetration of clavulanic acid observed in this study is likely to contribute to the efficacy of clavulanic acid/beta-lactam combinations in combating beta-lactam resistant bacterial pathogens.

Comparison of cefuroxime axetil and amoxicillin/clavulanate in the treatment of acute bacterial sinusitis

This double-masked, multicenter, randomized clinical trial compared the efficacy and tolerability of cefuroxime axetil and amoxicillin/clavulanate in the treatment of acute bacterial maxillary sinusitis. A total of 263 patients with acute bacterial maxillary sinusitis were randomly assigned to receive 10 days of treatment with either cefuroxime axetil 250 mg twice daily (n = 132) or amoxicillin/clavulanate 500/125 mg 3 times daily (n = 131). Patients' responses to treatment were assessed once during treatment (6 to 8 days after the start of treatment), at the end of treatment (1 to 3 days posttreatment), and at follow-up (26 to 30 days after cessation of treatment). Clinical success, defined as cure or improvement, was equivalent in the cefuroxime axetil and amoxicillin/ clavulanate groups at the end-of-treatment and follow-up assessments. Patients in both groups showed improvements in symptoms of acute sinusitis at the during-treatment visit. Treatment with amoxicillin/clavulanate was associated with a significantly higher incidence of drug-related adverse events than treatment with cefuroxime axetil (29% vs 17%), primarily reflecting a higher incidence of gastrointestinal adverse events (23% vs 11%), particularly diarrhea. Two patients in the cefuroxime axetil group and 8 patients in the amoxicillin/clavulanate group withdrew from the study due to adverse events (P = 0.06). These results indicate that cefuroxime axetil 250 mg twice daily is as effective as amoxicillin/clavulanate 500 mg 3 times daily in the treatment of acute sinusitis and produces fewer gastrointestinal adverse events. cefuroxime axetil, amoxicillin/clavulanate, acute sinusitis.