Aztreonam concentration in abdominal tissues and bile

Antibiotics in the Biliary Tract: A Review of the Pharmacokinetics and Clinical Outcomes of Antibiotics Penetrating the Bile and Gallbladder Wall

Biliary tract infections (BTIs), including cholangitis and cholecystitis, are common causes of bacteremia. Bacteremic BTIs are associated with a mortality rate of 9-12%. The extent to which antibiotics are excreted in the bile and the ratio of their exposure to the minimum inhibitory concentration of the infecting organism are among the important factors for the treatment of BTIs. This review updates health care professionals on the distribution of antibiotics in the common bile duct, gallbladder, and gallbladder wall. Antibiotic efficacy in treating BTIs based on the latest available clinical studies is also discussed. The efficacy and pharmacokinetics of 50 antibiotics are discussed. Overall, most antibiotic classes exhibit biliary penetration that translates into clinical efficacy. Only seven antibiotics (amoxicillin, cefadroxil, cefoxitin, ertapenem, gentamicin, amikacin, and trimethoprim/sulfamethoxazole) had poor biliary penetration profiles. Three antibiotics (ceftibuten, ceftolozane/tazobactam, and doripenem) had positive clinical outcomes despite the lack of pharmacokinetic studies on their penetration into the biliary tract. Conflicting efficacy data were reported for ampicillin despite adequate biliary penetration, whereas conflicting pharmacokinetic data were reported with cefaclor and moxifloxacin. Even in the absence of supportive clinical studies, antibiotics with good biliary penetration profiles may have a place in the treatment of BTIs.

A review of the pharmacokinetics and pharmacodynamics of aztreonam

The monobactam aztreonam is currently being re-examined as a therapeutic agent in light of the global spread of carbapenem resistance in aerobic Gram-negative bacilli and aztreonam's stability to Ambler class B metallo-β-lactamases. Of particular interest are the pharmacokinetic and pharmacodynamic properties of aztreonam alone and in combination with β-lactamase inhibitors. The choice of inhibitor may vary depending on the spectrum of β-lactamases produced by Enterobacteriaceae. The monobactam ring is also being used to produce new developmental monobactams. Thus, a greater understanding of aztreonam pharmacokinetics and dynamics is of great relevance in drug development. This review summarizes the pharmacokinetic profile of aztreonam in man and its pharmacodynamics in human and pre-clinical studies when studied alone and with β-lactamase inhibitors.

Empiric antibiotic use--aztreonam as a model

Empiric antibiotic therapy, which accounts for over 90 percent of in-hospital therapeutic antibiotic decisions, may be defined as tentative therapy designed to decrease morbidity and mortality associated with severe infection due to unidentified bacterial pathogens. In the 48- to 72-hour interim between presentation and the availability of reliable culture and sensitivity data that allow for definitive therapy, empiric therapy is extremely important. Aztreonam, the first member of the monobactam class of monocyclic beta-lactam antibiotics, is highly active against most gram-negative aerobic bacteria, including Pseudomonas aeruginosa. Its spectrum of activity is similar to that of the aminoglycosides but without the toxicity associated with those agents. For this reason, aztreonam may play an important role in empiric therapy. Currently, it can be recommended as single-agent empiric therapy only for severe urinary tract infections, but in combination with a variety of other agents, it has proved useful against a wide range of bacterial infections, and in certain subgroups, such as penicillin-allergic patients, it may represent the treatment of choice. It is not yet clear whether aztreonam is superior to other relatively nontoxic agents, such as the third-generation cephalosporins or carbapenems, but there is little doubt that this new agent is a generally safe and effective drug for the treatment of suspected gram-negative sepsis.

Aztreonam can safely be used in combination with cyclosporin without aggravating nephrotoxicity

The administration of antibiotics to renal transplant patients using cyclosporin can be difficult because of the risk of severe nephrotoxicity. An investigation was therefore carried out to determine whether aztreonam, a synthetic monocyclic beta-lactam antibiotic, can safely be combined with cyclosporin. In this retrospective study 68 renal transplant patients who received preoperative antibiotic prophylaxis consisting of aztreonam, ampicillin, and lincomycin were compared with 68 patients who received ceftazidime instead of aztreonam. Both groups were treated with cyclosporin and prednisolone and followed for 3 months. After transplantation 28.7% of the patients suffered from an acute renal failure and 1.5% had a wound infection. There were no significant differences between the two groups in acute renal failure, would infections, other infections, incidence of rejections, duration of admission, or graft survival. We therefore conclude that aztreonam can safely be administered together with cyclosporin. We also conclude that the combination of aztreonam, ampicillin, and lincomycin is a good preoperative antibiotic prophylaxis in renal transplant patients.

A comparison of monobactam antibiotics in surgical infections

The introduction of gentamicin almost 20 years ago provided an effective option for the treatment of gram-negative bacillary infections. During the past few years, the availability of aztreonam (a monobactam), imipenem (a carbapenem), and newer cephalosporins within vitro activities comparable with aminoglycosides against many gram-negative bacilli, has stimulated a reassessment of the role of aminoglycosides in treating these infections. When determining the role of new antimicrobials as potential replacements for more established agents, the clinical focus should be on three factors: comparative efficacy, safety, and cost. Consideration of cost is relevant only when efficacy and safety are equivalent. Other factors, such as comparative in vitro antimicrobial activity, pharmacokinetics, and effect on normal flora can also influence the selection of an antimicrobial regimen. A new class of antimicrobials, the monobactams, is the focus of this review. The only member of this class currently in clinical use is aztreonam. A comparison with aminoglycosides is particularly relevant because aztreonam is active against aerobic gram-negative bacilli. This review will discuss the acknowledged concerns with aminoglycoside use and compare the characteristics of aztreonam and currently marketed aminoglycosides.