A Clinical Review and Critical Evaluation of Imipenem-Relebactam: Evidence to Date

Imipenem-relebactam (I-R) is a novel beta-lactam/beta-lactamase inhibitor combination given with cilastatin. It is indicated for the treatment of complicated urinary tract infections, complicated intra-abdominal infections, and hospital-acquired or ventilator-associated bacterial pneumonia. A literature search was completed to evaluate the evidence to date of I-R. I-R has in vitro activity against multidrug-resistant organisms including carbapenem-resistant Pseudomonas aeruginosa and extended-spectrum beta-lactamase and carbapenem-resistant Enterobacterales. It was granted FDA approval following the promising results of two phase II clinical trials in patients with complicated urinary tract infections and complicated intra-abdominal infections. The most common adverse drug events associated with I-R were nausea (6%), diarrhea (6%), and headache (4%). I-R is a new beta-lactam/beta-lactamase inhibitor combination that will be most likely used for patients with multidrug-resistant gram-negative infections in which there are limited or no available alternative treatment options.

Single-Center Pharmacokinetic Study and Simulation of a Low Meropenem Concentration in Brain-Dead Organ Donors

Meropenem is an ultrabroad-spectrum antibiotic of the carbapenem family. In brain-dead organ donors, administration of standard meropenem dosages does not reach therapeutic levels. Our objectives were to determine the plasma concentration of meropenem after the administration of standard meropenem dose and to estimate an improved dosage regimen for these patients. One gram of meropenem was administered as a 1-h infusion every 8 h for 1 to 3 days, and blood samples were collected. The plasma concentration of meropenem was measured and subjected to pharmacokinetic analysis. Simcyp simulation was performed to predict the optimum plasma levels and dosage based on the patients' individual pharmacokinetic parameters. The maximum plasma concentration of meropenem was 3.29 μg/ml, which was lower than four times the MIC of 8 μg/ml. Although the mean creatinine clearance of patients was moderately low (67.5 ml/min), the apparent volume of distribution at steady state (Vss) and time-averaged total body clearance (CL) of meropenem were markedly elevated (4.97 liters/kg and 2.06 liters/h/kg, respectively), owing to massive fluid loading to decrease the high sodium levels and to treat shock or dehydration. The simulation revealed that dose and infusion time of meropenem should be increased based on patients' Vss and CL, and a loading dose is recommended to reach rapidly the target concentration. In conclusion, a standard meropenem regimen is insufficient to achieve optimal drug levels in brain-dead patients, and an increase in dose and extended or continuous infusion with intravenous bolus administration of a loading dose are recommended for these patients.

Meropenem: a new carbapenem antimicrobial

OBJECTIVE

To describe and then compare an investigational carbapenem antibiotic, meropenem, with the only currently available antibiotic in this class, imipenem/cilastatin.

DATA IDENTIFICATION

An English language search using MEDLINE (1988-1993); Abstracts of the 31st Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), 1991; and Abstracts of the 32nd ICAAC, 1992.

STUDY SELECTION

All current scientific publications were reviewed for study design and quality. Emphasis was placed on susceptibility and pharmacokinetic analysis. Phase 3 clinical trials are now being completed and have only been published in abstract form. Hence, conclusions derived regarding efficacy were tempered.

RESULTS

Meropenem is active against a broad spectrum of gram-positive and -negative pathogens including beta-lactamase producers. Meropenem appears to be two- to fourfold less active than imipenem against gram-positive organisms. Meropenem is two- to fivefold more active against enterobacteriaceae. The two compounds appear to be equally active against Pseudomonas aeruginosa. Pharmacokinetic disposition is also similar for imipenem and meropenem. Meropenem may exhibit greater tissue penetration. Meropenem is not labile to renal hydrolysis and can be administered without a competitive antagonist of dihydropeptidase, such as cilastatin. In clinical trials, meropenem appears to be as safe and effective as imipenem/cilastatin or ceftazidime in the treatment of infections involving soft tissue, urinary tract, upper respiratory tract, abdominal processes, and febrile neutropenic episodes.

CONCLUSIONS

Meropenem is comparable to imipenem in terms of in vitro susceptibility pattern and pharmacokinetic disposition. Overall, meropenem seems to offer promise as the second of the carbapenem class of antibiotics. Clinical data are preliminary, and further data are needed.

Newer cephalosporins: lessons to be learned from clinical trials in intraabdominal infections

Recent clinical trials testing the efficacy of newer cephalosporins in intraabdominal infections lack a number of the study design criteria proposed by Solomkin et al. Nevertheless, these trials all support the use of these newer cephalosporins in the treatment of intraabdominal infections. These newer agents demonstrate increased in vitro antimicrobial activity against potential aerobic pathogens, which suggests that they may be used in combination with an antianaerobic drug in the treatment of intraabdominal infections. Therefore, agents including cefotaxime, cefoperazone, ceftazidime, cefuroxime, ceftriaxone, and aztreonam may be chosen in place of the standard aminoglycoside. Previous studies have demonstrated the necessity of both aerobic and anaerobic coverage in empiric therapy of intraabdominal infections. Cefotetan, ceftizoxime, cefoxitin, moxalactam, mezlocillin, and piperacillin all have in vitro activity against aerobes and anaerobes (including B. fragilis), thus, these agents have a potential as monotherapy for acute intraabdominal infections in otherwise healthy patients. Directed combination chemotherapy or perhaps imipenem alone is recommended for persistent peritonitis and intraabdominal infections in immunocompromised hosts.

Recent developments in chemotherapy of ocular diseases

The profile of organisms responsible for ocular infections has changed over the past few decades. Although nonresistant and resistant staphylococci still lead the list, gram-negative, mixed infections and anaerobic organisms have become more evident. In spite of more potent and broader spectra antibiotics, resistant organisms still emerge. The therapy of intraocular infections requires an awareness of the latest antibiotics, particularly their advantages, limitations, toxicities, and administration. Iontophoresis through the sclera overlying the pars planum area with small diameter applicators may offer another route of administration which may reduce or eliminate the value of direct intravitreal injections of antibiotics. Reduction of the harmful effects of endotoxins of organismal origin might minimize the adverse effects of intraocular infection, particularly after gram-negative invasion. The choice of antibiotic may influence the quantities of endotoxins released.