In vitro activity of ertapenem against common clinical isolates in relation to human pharmacokinetics

APPROPRIATE AND TIMELY EMPIRICAL ANTIMICROBIAL TREATMENT OF ICU INFECTIONS - A ROLE FOR CARBAPENEMS

Treatment of serious nosocomial infections in the intensive care unit requires swift, effective, well-tolerated and appropriate therapy from the outset. The consequences of inappropriate treatment, i.e. the use of antibiotics that are ineffective against the causative pathogen(s) or delayed therapy, are numerous and impact negatively upon both the patient and the ever-dwindling healthcare resources in many hospitals. Although antibiotics have revolutionised the treatment of infections, their inappropriate and untimely use within the intensive care setting has led to the emergence and spread of antibiotic-resistant bacteria worldwide. Consequently, to ensure successful patient outcomes (reduce morbidity and mortality), it is important that any antibiotic treatment employed is right first time. Treatment of serious infections in the intensive care unit requires an empirical stratagem providing broad-spectrum coverage to a wide range of suspected or difficult-to-treat pathogens such as Pseudomonas aeruginosa. However, to prevent the errors of the past, this needs to be tailored as soon as the pathogen has been identified and resistance patterns are known. The carbapenems are potent parenteral antibiotics, with an ultra-broad spectrum of activity that encompasses multi-drug resistant and difficult-to-treat Gram-negative bacteria. Clinical trial data supports the clinical effectiveness of these agents in patients with difficult to treat pathogens.

Design, synthesis, and evaluation of prodrugs of ertapenem

Carbapenems are intravenous lifesaving hospital antibiotics. Once patients leave the hospital, they are sent home with antibiotics other than carbapenems since they cannot be administered orally due to lack of oral absorption primarily because of very highly polarity. A prodrug approach is a bona fide strategy to improve oral absorption of compounds. Design and synthesis, in vitro and in vivo evaluation of diversified prodrugs of ertapenem, one of the only once daily dosed carbapenems is described. Many of the prodrugs prepared for evaluation are rapidly hydrolyzed in rat plasma. Only bis-(5-methyl-2-oxo-1,3-dioxol-4-yl)methyl (medoxomil) ester prodrug was rapidly hydrolyzed in most of the plasmas including rat, human, dog, and monkey. Although the rate of conversion of ertapenem diethyl ester prodrug (6) was slow in in vitro plasma hydrolysis, it showed the best in vivo pharmacokinetic profile in dog by an intraduodenal dosing giving >31% total oral absorption.

Management of Complicated Appendicitis and Comparison of Outcome with Other Primary Sites of Intra-abdominal Infection: Results of a Trial Comparing Ertapenem and Piperacillin-Tazobactam

A post-hoc analysis of data from a trial of complicated intra-abdominal infection was performed to compare the demographic and disease characteristics of patients with complicated appendicitis to those whose primary infection involved other intra-abdominal sites, assess the impact of site of primary infection on outcome, and compare the efficacy and safety of ertapenem 1 g daily with piperacillin-tazobactam 3.375 g every 6 h for treatment of complicated appendicitis. Compared with patients who had primary infection of the colon or another site in the abdomen, patients with complicated appendicitis were younger, had less severe disease (based on lower APACHE II score and lower proportion with generalized peritonitis), and were less likely to be managed by percutaneous drainage of an abscess or to have a postoperative infection. Patients with complicated appendicitis were more likely to have a favorable outcome than were patients with infection of the colon (OR, 3.02; 95% CI, [1.54-5.901; P = .001). At the test-of-cure assessment, 109/123 (88.6%) microbiologically evaluable patients with complicated appendicitis who received ertapenem and 102/113 (90.3%) who received piperacillin-tazobactam had a favorable combined clinical and microbiologic outcome. The frequency and severity of drug-related adverse events were similar in the two treatment groups.

Prophylaxis with ertapenem in patients with obstructive jaundice undergoing endoscopic retrograde cholangiopancreatography: safety, efficacy, and biliary penetration

BACKGROUND

Cholangitis and biliary sepsis are rare but serious complications of endoscopic retrograde cholangiopancreatography (ERCP). The aim of this study is to investigate the safety, efficacy, and biliary penetration of ertapenem, a newer carbapenem with a long half-life and broad-spectrum antimicrobial activity, for ERCP prophylaxis.

METHODS

Patients with obstructive jaundice without cholangitis received a single dose of ertapenem equal to 1 gram intravenously prior to ERCP. A 2-3 mL bile sample was collected after cannulation and prior to contrast injection. Patients were observed for 72 hours for cholangitis or drug-related adverse events. Biliary ertapenem levels were measured using high-performance liquid chromatography (HPLC).

RESULTS

Twenty-eight patients (ages 18-87 years, M/F ratio 1:1) were enrolled. Seven had no cholestasis and were included to study ertapenem penetration in unobstructed biliary trees. Cannulation was achieved in all patients. One patient (3.6%) with persistent intrahepatic stones developed cholangitis. No drug-related adverse events were noted. The mean time from ertapenem administration to bile collection was 60 ± 24 minutes. There was a significant negative correlation between serum bilirubin and biliary ertapenem levels (r = -0.542, P = 0.003) with the highest level (6.25 μg/mL) noted in unobstructed biliary systems.

CONCLUSION

Ertapenem appears to be a safe and effective prophylaxis in patients with obstructive jaundice undergoing ERCP despite a limited biliary penetration in patients with high-grade obstruction.

Ertapenem: the new carbapenem 5 years after first FDA licensing for clinical practice

Ertapenem, a parenteral broad-spectrum 1-beta-methyl-carbapenem, was licensed 5 years ago for clinical practice in the US and Europe. The substance has a good in vitro activity against many common aerobic and anaerobic Gram-positive and -negative bacteria. Its in vitro activity against Enterobacteriaceae carrying plasmid- or chromosomal-mediated beta-lactamases, including AmpC- and extended-spectrum beta-lactamases, is especially clinically significant. Advantages concerning in vitro activity and low potential for so-called 'collateral damage', and development of own resistance during therapy, as shown in several randomized, controlled clinical trials, make ertapenem an excellent treatment choice for complicated aerobic and anaerobic mix infections caused by ertapenem-sensitive bacteria. On the other hand, due to its limited activity against Acinetobacter spp., enterococci and Pseudomonas aeruginosa, it is less suitable for late-onset nosocomial infections. International guidelines recommend the initial empirical use of ertapenem for intra-abdominal infections, skin and skin-structure infections, acute pelvic infections, complicated urinary tract infections and pneumonia (both community-acquired and 'early-onset' nosocomial) in a dose of 1.0 g administered once daily. However, recent results from pharmacokinetic/pharmacodynamic modelling studies in critically ill patients with ventilator-associated pneumonia and adipose volunteers with a body mass index of > or = 20 kg/m(2) showed that the standard dose of 1.0 g/day may not provide adequate free, protein-unbound drug concentrations in plasma and organ tissues. Therefore, a shortening of the dosage interval or continuous infusion of ertapenem should be considered to ensure optimal free concentrations in these particular populations.

Comparative Review of the Carbapenems

The carbapenems are beta-lactam antimicrobial agents with an exceptionally broad spectrum of activity. Older carbapenems, such as imipenem, were often susceptible to degradation by the enzyme dehydropeptidase-1 (DHP-1) located in renal tubules and required co-administration with a DHP-1 inhibitor such as cilastatin. Later additions to the class such as meropenem, ertapenem and doripenem demonstrated increased stability to DHP-1 and are administered without a DHP-1 inhibitor. Like all beta-lactam antimicrobial agents, carbapenems act by inhibiting bacterial cell wall synthesis by binding to and inactivating penicillin-binding proteins (PBPs). Carbapenems are stable to most beta-lactamases including AmpC beta-lactamases and extended-spectrum beta-lactamases. Resistance to carbapenems develops when bacteria acquire or develop structural changes within their PBPs, when they acquire metallo-beta-lactamases that are capable of rapidly degrading carbapenems, or when changes in membrane permeability arise as a result of loss of specific outer membrane porins. Carbapenems (imipenem, meropenem, doripenem) possess broad-spectrum in vitro activity, which includes activity against many Gram-positive, Gram-negative and anaerobic bacteria; carbapenems lack activity against Enterococcus faecium, methicillin-resistant Staphylococcus aureus and Stenotrophomonas maltophilia. Compared with imipenem, meropenem and doripenem, the spectrum of activity of ertapenem is more limited primarily because it lacks activity against Pseudomonas aeruginosa and Enterococcus spp. Imipenem, meropenem and doripenem have in vivo half lives of approximately 1 hour, while ertapenem has a half-life of approximately 4 hours making it suitable for once-daily administration. As with other beta-lactam antimicrobial agents, the most important pharmacodynamic parameter predicting in vivo efficacy is the time that the plasma drug concentration is maintained above the minimum inhibitory concentration (T>MIC). Imipenem/cilastatin and meropenem have been studied in comparative clinical trials establishing their efficacy in the treatment of a variety of infections including complicated intra-abdominal infections, skin and skin structure infections, community-acquired pneumonia, nosocomial pneumonia, complicated urinary tract infections, meningitis (meropenem only) and febrile neutropenia. The current role for imipenem/cilastatin and meropenem in therapy remains for use in moderate to severe nosocomial and polymicrobial infections. The unique antimicrobial spectrum and pharmacokinetic properties of ertapenem make it more suited to treatment of community-acquired infections and outpatient intravenous antimicrobial therapy than for the treatment of nosocomial infections. Doripenem is a promising new carbapenem with similar properties to those of meropenem, although it appears to have more potent in vitro activity against P. aeruginosa than meropenem. Clinical trials are required to establish the efficacy and safety of doripenem in moderate to severe infections, including nosocomial infections.

Ertapenem: a review of its use in the treatment of bacterial infections

The Group 1, 1 beta-methyl carbapenem ertapenem (Invanz) is approved for parenteral use in patients with complicated intra-abdominal infection (cIAI), community-acquired pneumonia (CAP) and acute pelvic infection caused by susceptible strains of certain designated organisms in both the US and the EU. Additional approved indications in the US include complicated skin and skin structure infection (cSSSI) and complicated urinary tract infection (cUTI). Ertapenem is approved for use in adults in both the US and the EU and in paediatric patients aged >or=3 months in the US. Ertapenem has a broad spectrum of in vitro activity against Gram-negative pathogens, including extended-spectrum beta-lactamase (ESBL)- and AmpC-producing Enterobacteriaceae, Gram-positive pathogens and anaerobic pathogens. It has similar efficacy to comparator antibacterials such as piperacillin/tazobactam in cSSSI (including diabetic foot infection), cIAI and acute pelvic infection and ceftriaxone with or without metronidazole in cIAI, cUTI and CAP. The drug has also shown efficacy in the treatment of paediatric patients with complicated community-acquired bacterial infections. Ertapenem has a convenient once-daily administration schedule and is generally well tolerated. Thus, ertapenem is an important option for the empirical treatment of complicated community-acquired bacterial infections in hospitalised patients.

Intraabdominal tissue concentration of ertapenem

OBJECTIVES

Ertapenem, a class I carbapenem, is approved for the treatment of mild to severe intraabdominal infections, but its in vivo concentrations in intraabdominal tissues are unknown. The purpose of this study was to determine the concentration of ertapenem in intraabdominal tissue.

PATIENTS AND METHODS

After informed consent 48 patients, 23 female and 25 male with a median age of 58 years (34-81), requiring surgical intervention at intraabdominal organs were enrolled. Patients received 1 g of ertapenem intravenously for perioperative prophylaxis. Tissue samples were taken after resection of parts of the organs. Plasma samples were taken when tissue samples were taken. Drug concentrations were determined by liquid chromatography/mass spectrometry. An ANCOVA test (analysis of covariance) was performed to assess organ-specific differences in ertapenem concentration and penetration ratios.

RESULTS

Mean+/-SD ertapenem tissue concentration (mg/kg) was 16.0+/-8.8 in the gall bladder, 12.1+/-5.3 in the colon, 7.0+/-5.7 in the small bowel, 4.5+/-2.3 in the liver and 3.4+/-2.9 in the pancreas. The mean tissue/plasma ratio was 0.19 (colon), 0.17 (small bowel), 0.17 (gall bladder), 0.088 (liver) and 0.095 (pancreas). The ANCOVA test revealed statistically significant organ-specific differences in ertapenem tissue concentration in the gall bladder versus liver/pancreas and in tissue penetration for the colon versus liver/pancreas.

CONCLUSIONS

These pharmacokinetic results support the assumption that ertapenem is suitable for the treatment of intraabdominal infections.

Ertapenem: review of a new carbapenem

The carbapenems are beta-lactam-type antibiotics with an exceptionally broad spectrum of activity. Ertapenem is a new carbapenem developed to address the pharmacokinetic shortcomings (short half-life) of imipenem and meropenem. Ertapenem shares similar structural features with meropenem, including its stability to dehydropeptidase-1, allowing it to be administered without a dehydropeptidase-1 inhibitor. Ertapenem, like imipenem and meropenem, demonstrates broad-spectrum antimicrobial activity against many Gram-positive and -negative aerobes and anaerobes and is resistant to nearly all beta-lactamases, including extended-spectrum beta-lactamases and AmpCs. However, it differs from both imipenem and meropenem in demonstrating limited activity against Enterococcusspp., Pseudomonasaeruginosa and other nonfermentative Gram-negative bacteria commonly associated with nosocomial infections. The extensive protein binding of ertapenem extends the half-life and allows for once-daily dosing. Prospective, multicenter, randomized, double-blind, comparative clinical studies demonstrate similar clinical efficacy of ertapenem compared with other agents. Clinical trials of complicated intra-abdominal infection, acute pelvic infection, complicated skin and soft-structure infection, community-acquired pneumonia and complicated urinary tract infections demonstrated that ertapenem has equivalent efficacy and safety compared with ceftriaxone and piperacillin/tazobactam. Ertapenem is a promising new carbapenem with excellent efficacy and safety for the treatment of a variety of community-acquired infections. It also appears to be of great value as an outpatient parenteral antimicrobial therapy.

Pharmacokinetics of total and unbound ertapenem in healthy elderly subjects

Ertapenem is a new once-a-day parenteral carbapenem antimicrobial agent. The pharmacokinetics of unbound and total concentrations of ertapenem in plasma were investigated in elderly subjects and compared with historical data from young adults. In a single- and multiple-dose study, healthy elderly males and females (n = 14) 65 years old or older were given a 1-g intravenous (i.v.) dose once daily for 7 days. Plasma and urine samples collected for 24 h on days 1 and 7 following administration of the 1-g doses were analyzed by reversed-phase high-performance liquid chromatography. Areas under the concentration-time curve from 0 h to infinity (AUC(0- infinity )) for elderly females and males were similar following administration of 1-g single i.v. doses, and thus, the genders were pooled in subsequent analyses. Concentrations in plasma and the half-life of ertapenem were generally higher and longer, respectively, in elderly subjects than in young adults. The mean AUC(0- infinity ) of total ertapenem in the elderly was 39% higher than that in young subjects following administration of a 1-g dose. The differences were slightly greater for the mean AUC(0- infinity ) of unbound ertapenem (71%). The unbound fraction of ertapenem in elderly subjects ( approximately 5 to 11%) was generally greater than that in young adults ( approximately 5 to 8%). As in young adults, ertapenem did not accumulate upon multiple dosing in the elderly. The pharmacokinetics of ertapenem in elderly subjects, while slightly different from those in young adults, do not require a dosage adjustment for elderly patients.

Ertapenem: a review of its use in the management of bacterial infections

Ertapenem, a carbapenem antibacterial, has in vitro activity against many Gram- negative (including Enterobacteriaceae) and Gram-positive aerobic and anaerobic bacteria that are commonly associated with various infections.Once-daily parenteral (intravenous or intramuscular) ertapenem 1g was as effective as comparator antimicrobial agents (piperacillin/tazobactam or ceftriaxone +/- metronidazole) in patients with bacterial infections in randomised, double-blind, multicentre clinical trials. Response rates with ertapenem were 84% and 87% (combined microbiological and clinical) in patients with complicated intra-abdominal infections (CIAI), 82% (clinical) in patients with complicated skin and skin structure infections (CSSSI), 86% and 92% (microbiological) in patients with complicated urinary tract infections (CUTI), 92% (clinical) in patients with community-acquired pneumonia (CAP) associated with typical pathogens and 94% (clinical) in patients with acute pelvic infection. Respective response rates were statistically equivalent to those with comparators (81-94%). The efficacy of ertapenem was equivalent to that of piperacillin/tazobactam in patients infected with Enterobacteriaceae or anaerobes and to ceftriaxone in patients infected with Enterobacteriaceae. Ertapenem was generally well tolerated by patients with bacterial infections, with most adverse events being mild to moderate in severity. The most common ertapenem-associated adverse events were diarrhoea, infused vein complication, nausea, headache, vaginitis in females, phlebitis and/or thrombophlebitis and vomiting.

CONCLUSION

Ertapenem is a broad-spectrum parenteral antibiotic with activity against many Gram-negative (including Enterobacteriaceae) and Gram-positive aerobic and anaerobic bacteria and is suitable for once-daily administration. Ertapenem has a role in the treatment of CAP associated with typical respiratory pathogens and is of particular value in the treatment of polymicrobial infections (such as CIAI, CSSSI, CUTI and acute pelvic infections), especially where Enterobacteriaceae and anaerobic bacteria are involved.