Potential of imipenem as single-agent empiric antibiotic therapy of febrile neutropenic patients with cancer

Optimizing empirical antimicrobial therapy for infection due to gram-negative pathogens in the intensive care unit: utility of a combination antibiogram

OBJECTIVE

To determine whether the use of dual antimicrobial therapy based on the results of a combination antibiotic susceptibility report (antibiogram) increases the likelihood of selecting adequate empirical coverage in critically ill patients with infection due to potentially resistant gram-negative pathogens.

DESIGN

Retrospective data analysis.

SETTING

Urban academic medical center.

METHODS

An analysis of culture results and susceptibility data from intensive care unit patients determined by the clinical microbiology laboratory was performed. The proportion of 5 common gram-negative pathogens susceptible to monotherapy with 1 of 3 antipseudomonal antibiotics (piperacillin-tazobactam, ceftazidime, or imipenem) was compared with the proportion susceptible to each of these 3 "backbone" agents plus 1 of 4 additional antimicrobial agents used in combination.

RESULTS

More than 5,000 clinical isolates were examined. When all isolates recovered during the entire study period were included, the addition of any of the second antibiotics studied to each of the 3 backbone agents significantly increased the likelihood of covering the causative pathogen (P < .01 for each). The benefit of combination therapy was variable when results for each of the 5 organisms were examined individually. When temporal trends in susceptibility were examined, the decrease in the proportion of organisms susceptible to monotherapy was statistically significant for both imipenem and ceftazidime (P < .01).

CONCLUSIONS

Reporting antibiotic susceptibility data in the form of a combination antibiogram may be useful to clinicians who are considering empirical antimicrobial therapy in the intensive care unit.

Microdialysis study of imipenem distribution in skeletal muscle and lung extracellular fluids of noninfected rats

The aim of this study was to investigate the imipenem distribution in muscle and lung interstitial fluids by microdialysis in rats and to compare the free concentrations in tissue with the free concentrations in blood. Microdialysis probes were inserted into the jugular vein, hind leg muscle, and lung. Imipenem recoveries in these three media were determined in each rat by retrodialysis by drug period before drug administration. Imipenem was infused intravenously at a dose of 120 mg . kg-1 over 30 min, and microdialysis samples were collected for 150 min. The whole study was conducted with nonhydrated rats (n=4) and hydrated rats (n=6) while the animals were under isoflurane anesthesia. The decay of free concentrations in blood, muscle, and lung with time were monoexponential; and the concentration profiles in these three media were virtually superimposed in both groups. Accordingly, the ratios of the area under the curve (AUC) for tissue (muscle or lung) to the AUC for blood were always virtually equal to 1. Compared to values previously determined with awake rats, clearance was reduced by 2 and 1.5 in nonhydrated and hydrated rats, respectively, but the volume of distribution was unchanged. By combining microdialysis in blood and tissues, it was possible to demonstrate that free imipenem concentrations were virtually identical in blood, muscle, and lung.

The Importance of Bactericidal Drugs: Future Directions in Infectious Disease

BACKGROUND

Although a considerable amount of research has gone into the study of the role of bactericidal versus bacteriostatic antimicrobial agents in the treatment of different infectious diseases, there is no accepted standard of practice.

METHODS

A panel of infectious diseases specialists reviewed the available literature to try to define specific recommendations for clinical practice.

RESULTS

In infections of the central nervous system, the rapidity with which the organism is killed may be an important determinant, because of the serious damage that may occur during these clinical situations. The failure of bacteriostatic antibiotics to adequately treat endocarditis is well documented, both in human studies and in animal models.

CONCLUSION

The bulk of the evidence supports the concept that, in treating endocarditis and meningitis, it is important to use antibacterial agents with in vitro bactericidal activity. This conclusion is based on both human and animal data. The data to support bactericidal drugs' superiority to bacteriostatic drugs do not exist for most other clinical situations, and animal models do not support this concept in some situations. Clinicians should be aware that drugs that are bacteriostatic for one organism may in fact be bactericidal for another organism or another strain of the same organism.

Empiric antimicrobial therapy of febrile neutropenic patients undergoing haematopoietic stem cell transplantation

This study was conducted to assess the efficacy and toxicity of intravenous (i.v.) ceftazidime and ciprofloxacin in neutropenic febrile patients undergoing high dose myeloablative therapy and hematopoietic stem cell transplantation (HSCT). All patients undergoing HSCT for leukaemia, lymphoma, multiple myeloma and solid tumours received open-label ceftazidime 2 g i.v. every 8 h and ciprofloxacin 400 mg i.v. every 12 h if they developed fever while they were neutropenic. Success with or without modification of this regimen was defined as survival through the neutropenic period; failure was defined as death secondary to infection. Of 106 patients treated with this regimen, the success rate was 99%. Sixty-one of the patients (57.5%) defervesced within 48-72 h and remained afebrile without regimen modification. In 41.5% of the cases (44/106), the regimen was modified because of persistent fever. One patient died secondary to sepsis. The combination of ceftazidime and ciprofloxacin as initial empiric antibacterial therapy in febrile neutropenic patients undergoing myeloablative therapy and HSCT is highly effective and is associated with minimal toxicity.

Ceftazidime and ciprofloxacin as empiric therapy in febrile neutropenic patients undergoing hematopoietic stem cell transplantation

This pilot study was done to assess the efficacy and toxicity of intravenous ceftazidime and ciprofloxacin in patients developing febrile neutropenia while undergoing high-dose myeloablative therapy and hematopoietic stem cell transplantation (HSCT). All patients undergoing high-dose chemoradiotherapy and HSCT for leukemias, lymphomas, multiple myeloma, and solid tumors received open-label ceftazidime 2 g intravenously every 8 hours and ciprofloxacin 400 mg intravenously every 12 hours if they developed fever while they were neutropenic. Success with or without modification of this regimen was defined as survival through the neutropenic period; failure was defined as death secondary to infection. Among 45 patients treated with this regimen, the success rate was 98%. Sixty-two percent (28 of 45) of the patients achieved defervescence within 48 to 72 hours and remained afebrile without regimen modification. In 16 patients (36%) the regimen was modified because of persistent fever. The combination of ceftazidime and ciprofloxacin as initial empiric antibacterial therapy in febrile neutropenic patients undergoing myeloablative therapy and HSCT appears to be highly effective and is associated with minimal toxicity.

Randomised comparison of ceftazidime and imipenem as initial monotherapy for febrile episodes in neutropenic cancer patients

With the availability of new, broad-spectrum antibiotics, initial therapy with a single agent has become an alternative to classic combinations in the management of febrile, neutropenic cancer patients. The aims of this study were to compare the efficacy of ceftazidime and imipenem as empirical monotherapy of febrile episodes in neutropenic patients, and to examine the frequency with which second-line antibiotics (amikacin, vancomycin, or both) were required. A prospective clinical trial was carried out in a single centre. Eligible patients with solid tumours or lymphoma were randomised to receive monotherapy with ceftazidime or imipenem. In the event of no response, amikacin and/or vancomycin were added in 48-72 h intervals (sequentially, or according to clinical or microbiological data). Efficacy was evaluable for 111 assessable episodes. Median neutrophil count at entry was 100 cells/microliters and median duration of neutropenia was 4 days. Febrile episodes were classified as microbiologically (34%) or clinically documented (42%), and fever of unknown origin (24%). Gram-negative infections (57%) predominated over gram-positive isolates (30%). The overall success rate with monotherapy (69% versus 70%), or with modification (20% versus 23%) were equivalent for ceftazidime and imipenem (P = 0.75). The mortality in this series was 5%. Single-agent therapy with either ceftazidime or imipenem is effective for the empirical treatment of febrile episodes in neutropenic patients with solid tumours. Early addition of amikacin and/or vancomycin resolves most failures of the first step.

Feasibility of outpatient management of fever in cancer patients with low-risk neutropenia: results of a prospective randomized trial

PURPOSE

We recently demonstrated the efficacy of single-agent oral ofloxacin in the management of hospitalized neutropenic febrile patients. Ofloxacin was particularly effective in patients with short duration of neutropenia and fever of undetermined origin. These results prompted us to study the feasibility of outpatient management of neutropenic febrile patients who are otherwise at low risk of morbidity and mortality.

PATIENTS AND METHODS

This multi-institutional, prospective, randomized trial included 182 low-risk neutropenic febrile episodes. After an initial work-up for fever, patients were randomized to receive oral ofloxacin 400 mg immediately and twice daily thereafter in the hospital or as outpatients. Close monitoring and follow-up were carried out in all patients. Those who failed to respond and remained febrile were given parenteral antibiotics. Nonresponding outpatients were admitted to the hospital for parenteral therapy.

RESULTS

One hundred sixty-nine episodes were evaluable. The hospital and outpatient treatment groups had comparable clinical characteristics. Pyrexias of undetermined origin (PUO) comprised 69% of episodes managed in hospital and 73% of episodes treated outside. The success rate with PUO was similar with inpatient and outpatient management. Patients with clinical and microbiologic infections fared less well than those with PUO. Overall, 78% of inpatient and 77% of outpatient fevers resolved with no modification of the initial treatment. Twenty-one percent of patients originally assigned to outside management required hospitalization. Mortality was 2% among inpatients and 4% among outpatients. One early death in a nonhospitalized patient underscores the need for close monitoring and surveillance in these cases.

CONCLUSIONS

Outpatient management of low-risk neutropenic febrile patients with ofloxacin is as effective as inpatient management with the same agent. This approach should be limited to the subset of patients with low-risk factors who are not otherwise on quinolone prophylaxis.

Comparison of imipenem pharmacokinetics in patients with acute or chronic renal failure treated with continuous hemofiltration

The total clearance of imipenem, a carbapenem antibiotic, is reduced from approximately 230 mL/min in patients with normal renal function to approximately 50 mL/min in patients with chronic renal failure. This decline in clearance results not only from the loss of renal clearance, but also from a reduction in the nonrenal clearance from 130 to 50 mL/min. Current dosing recommendations for the administration of imipenem to patients with acute or chronic renal failure are based on this reduced clearance rate. We investigated the pharmacokinetics of imipenem in critically ill patients with acute or chronic renal failure to determine whether published dosing guidelines were applicable to both patient populations. Imipenem pharmacokinetic parameters were determined in 10 anuric patients with renal failure managed by continuous venovenous hemofiltration (CVVH). Seven patients had acute renal failure, while the other three had preexisting chronic renal failure. Imipenem serum concentration data were incorporated into a first-order, single-compartment pharmacokinetic model. Determinations of the area under the serum concentration-time curve were made by the trapezoidal rule. Dosing regimens were calculated from clearance data to achieve a mid-dose imipenem serum concentration of 12 mg/L. The total clearance of imipenem in patients with acute renal failure (108.3 +/- 13.8 mL/min; mean +/- SD) was significantly greater than the total clearance measured in patients with chronic renal failure (64.4 +/- 10.5 mL/min; P < 0.02). This increased clearance resulted from a greater nonrenal clearance of the drug in patients with acute renal failure (95.0 +/- 13.8 v 51.1 +/- 10.5 mL/min; P < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Fever and granulocytopenia in children with cancer: a study of 299 episodes with two treatment protocols in Brazil

In Brazil, 226 children with cancer presenting 299 episodes of fever and neutropenia (< or = 500/mm3) were treated with two consecutive empirical regimens. Regimen I-Cefoxitin Amikacin-Carbenicillin; and Regimen II Ceftriaxone-Amikacin. 67.0% of the patients had leukemias or lymphomas, documented infections occurred in 47.2%, superinfections occurred in 18.7% (Reg. I) and 17.8% (Reg. II) of the episodes. The most common agents identified in Reg. I and Reg. II were, respectively, Gram negative rods (55.0%) and Gram positive cocci (52.6%). The overall rate of success with modifications (Amphotericin B, Vancomycin, Clindamycin, Metronidazole) was higher in Reg. II (93.0%) than in Reg. I (84.0%). This study shows that the appropriate formula to maximize the successful treatment of children with cancer, fever and neutropenia in developing nations includes adherence to established principles of supportive care, utilizing the optimal antibiotic agents available in the country. It is important to promote the necessary modifications along the treatment having in mind the high index of resistant agents.

Infections in the compromised host

The normal defense mechanisms against infection include (1) normal skin and mucous membranes, (2) humoral immunity, (3) phagocytic system, and (4) cellular immunity. The compromised (immunocompromised) host is an individual who has one or more deficiencies in these defense mechanisms. This article reviews potential infections in the compromised host as well as an approach to evaluation of these patients.

Randomised comparison of oral ofloxacin alone with combination of parenteral antibiotics in neutropenic febrile patients

Prompt treatment with empirical antibiotics in neutropenic febrile patients reduces morbidity and mortality. Most patients have been treated with parenteral combination antibiotics, but newer antibiotics with broad-spectrum bactericidal activity have made monotherapy feasible. Ofloxacin, a broad-spectrum fluoroquinolone, has the additional advantage that bactericidal concentrations can be achieved with oral administration. We have compared ofloxacin as an oral single agent with standard parenteral combination antibiotics for the management of neutropenic febrile patients in a prospective, randomised trial. Patients with severe neutropenia (absolute neutrophil count less than or equal to 0.5 x 10(9)/l), fever above 38 degrees C, and ability to take drugs by mouth were eligible for the study. After initial investigations, 60 patients were randomly assigned to oral ofloxacin 400 mg twice daily and 62 to parenteral combination antibiotic therapy (amikacin 15 mg/kg daily, plus, at various times in the trial, carbenicillin, cloxacillin, or piperacillin). Patients were examined 72 h and 7 days after the start of treatment and when neutropenia resolved. 24 (40%) ofloxacin-treated and 26 (42%) combination-treated patients had pyrexia of unknown origin (PUO). In both treatment groups, the treatment success rate was higher for such patients than for those with clinically or microbiologically documented infections (92% vs 67% [p less than 0.05] for ofloxacin; 85% vs 64% for combination). There were no significant differences in success rates of ofloxacin and combination treatment for these subgroups or overall (77% vs 73%). Patients with neutropenia for less than 1 week had better responses to both treatments than patients with longer-lasting neutropenia. There were 4 (7%) deaths in the ofloxacin group and 6 (10%) in the combination group. Both regimens were well tolerated. We conclude that oral single-agent ofloxacin is as effective as parenteral combination antibiotic therapy in neutropenic febrile patients, especially those expected to have short durations of neutropenia.

Ceftazidime versus imipenem-cilastatin as initial monotherapy for febrile neutropenic patients

One hundred febrile episodes in 89 neutropenic patients after cytotoxic chemotherapy were randomized to be treated with either ceftazidime or imipenem as initial monotherapy. The clinical characteristics of the two groups of patients were comparable. The response of the fever in patients who received imipenem was significantly better than that in those who received ceftazidime (77 versus 56%, respectively; P = 0.04), especially in those with microbiologically documented infection (81 versus 33%, respectively; P = 0.02). The in vitro susceptibilities and the clinical responses suggested that, with the possible exception of Pseudomonas spp., imipenem was more effective than ceftazidime in treating neutropenic infections caused by both gram-positive and -negative organisms. An additional 23 and 21% of the patients in the ceftazidime and imipenem groups, respectively, responded to the addition of cloxacillin and amikacin following failure of monotherapy. The majority of the treatment failures, relapses, and superinfections were related to resistant infective organisms such as methicillin-resistant Staphylococcus spp. and Pseudomonas spp. or disseminated fungal infections.

Imipenem/cilastatin versus piperacillin plus amikacin as empiric therapy in the treatment of febrile episodes in neutropenic patients with haematologic malignancies

Recently, new beta-lactam antibiotics, such as imipenem/cilastatin (IMP) with an unusually broad antibacterial spectrum and especially an adequate P. aeruginosa activity, have introduced the possibility of using prospective agent as empiric management of febrile granulocytopenic patients. We randomized 83 febrile neutropenic cancer patients for a prospective evaluation of two regimens: IMP versus piperacillin plus amikacin (PA). Both patients groups were similarly distributed with regard to age, sex, primary diagnosis and degree of granulocytopenia. More than 20% of the 74 evaluable patients had bacteraemia. The overall response rate for clinically or microbiologically documented infections was 90% in the IMP regimen versus 76% in the PA regimen, but statistical difference was not achieved. All bacteraemias in the IMP group but only 60% in the PA group were cured, however statistical difference was not achieved. IMP had to be discontinued in only one patient and the most common side effects were nausea and vomiting; no seizures were noted. Nephro- and ototoxicity, skin rash and bleeding have been the major side effects requiring drug discontinuation in 6 patients treated by PA. In conclusion, these data suggest that IMP used alone is safe and as effective as the combination of P plus A for the management of febrile granulocytopenic patients with haematologic malignancies. Further studies on a larger number of patients are needed to confirm these findings.

Infectious complications in childhood acute leukemias

Infectious complications in children with acute leukemias are reviewed as to incidence, predisposing factors, microbiologic etiologies and treatment. Principles of antimicrobiologic therapy are presented for bacterial, fungal, viral, and protozoal infections seen in children with cancer. Prevention of infection is also discussed.

Controlled trials of double beta-lactam therapy with cefoperazone plus piperacillin in febrile granulocytopenic patients

The efficacy and safety of double beta-lactam therapy with cefoperazone plus piperacillin in febrile granulocytopenic patients were compared with moxalactam plus piperacillin, ceftazidime plus piperacillin, and imipenem alone in two separate clinical trials. All patients also received prophylactic vitamin K. When National Committee for Clinical Laboratory Standards breakpoints for susceptibility were used, a greater proportion of pretherapy isolates of gram-negative aerobic bacilli and gram-positive organisms were found to be susceptible to cefoperazone (94 percent) and imipenem (91 percent) than to moxalactam (84 percent), ceftazidime (85 percent), or piperacillin (85 percent). In trial I, the overall response rates for documented or possible infections were 78 percent (76 of 97 patients) for cefoperazone/piperacillin and 80 percent (72 of 90 patients) for moxalactam/piperacillin. In trial II, the overall response rates were 86 percent (25 of 29 patients) for cefoperazone/piperacillin, 74 percent (20 of 27 patients) for ceftazidime/piperacillin, and 72 percent (21 of 29 patients) for imipenem alone. There was no nephrotoxicity or hemorrhage related to the study drugs. Diarrhea was more frequent with each of the double beta-lactam regimens, whereas nausea and seizures were more common with imipenem given at a dosage of 1.0 g intravenously every six hours. Seizures occurred in three of 29 imipenem-treated patients but in none of 243 patients treated with the double beta-lactam regimens (p less than 0.001). These results suggest that cefoperazone plus piperacillin provides adequate coverage for most common bacterial pathogens and is safe and effective therapy for febrile granulocytopenic patients.

Antibacterial therapy in patients with malignancies

Patients with malignant disease may be predisposed to bacterial infections because of neoplastic disruption of normal tissue barriers, exogenous immunosuppressive therapy (drugs with or without radiation), and intrinsic host immune deficits secondary to these diseases. Diminished polymorphonuclear leukocyte numbers or function and impaired humoral immunity are highly correlated with the development of serious bacterial infections. The usual signs and symptoms of infection may be absent or altered in a compromised host. Therapy must be instituted promptly upon clinical suspicion of bacterial infection, and empirical choices should usually include combinations that are synergistic for likely pathogens based on knowledge of the local predominant flora and susceptibility data. Synergism has most often been demonstrated in combinations that utilize a beta-lactam (semisynthetic penicillin or cephalosporin) and an aminoglycoside. Triple drug therapy has not been shown to be advantageous. Monotherapy with third generation cephalosporins, carbapenems, monobactams, or ureidopenicillins has not been proven to offer advantages over 2-drug regimens for these patients. Patients with blood deficient in granulocytes (granulocytopenic) who respond to 2-drug therapy but remain deficient in neutrophils (neutropenic) may need continued treatment until the neutropenia subsides. Those who do not respond and remain febrile with an unclear focus of infection may need to be started on antifungal therapy in addition to the antibacterial agent. The use of oral agents for the prophylaxis of neutropenic patients against bacteremia remains controversial. If drugs are used, co-trimoxazole and nystatin suspension may be preferable.

Steady-state pharmacokinetics of imipenem in febrile neutropenic cancer patients

We ascertained the pharmacokinetics of imipenem in febrile granulocytopenic cancer patients. The values observed were both different from and significantly more variable than those observed in normal volunteers. Free drug concentrations exceeded the MIC for 90% of Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus strains for greater than 6 h. The MIC for 90% of Pseudomonas aeruginosa strains was exceeded for 4 h. Because imipenem induces a 2-h postantibiotic effect in P. aeruginosa, it is promising as single-agent empiric therapy in this setting.

Synergism of the combinations of imipenem plus ciprofloxacin and imipenem plus amikacin against Pseudomonas aeruginosa and other bacterial pathogens

The combinations of imipenem plus ciprofloxacin and imipenem plus amikacin were investigated for their activity against Pseudomonas aeruginosa and other bacterial pathogens. For imipenem-susceptible P. aeruginosa, synergy of imipenem plus ciprofloxacin and imipenem plus amikacin was observed against 36 and 45% of the strains, respectively. The incidence of synergy against imipenem-resistant isolates of P. aeruginosa was 10% for both combinations. Antagonism was not observed with either combination.

Imipenem/cilastatin. A review of its antibacterial activity, pharmacokinetic properties and therapeutic efficacy

Imipenem is the first available semisynthetic thienamycin and is administered intravenously in combination with cilastatin, a renal dipeptidase inhibitor that increases urinary excretion of active drug. In vitro studies have demonstrated that imipenem has an extremely wide spectrum of antibacterial activity against Gram-negative and Gram-positive aerobic and anaerobic bacteria, even against many multiresistant strains of bacteria. It is very potent against species which elaborate beta-lactamases. Imipenem in combination with equal doses of cilastatin has been shown to be generally well tolerated and an effective antimicrobial for the treatment of infections of various body systems. It is likely to be most valuable as empirical treatment of mixed aerobic and anaerobic infections, bacteraemia in non-neutropenic patients and serious hospital-acquired infections.

A randomized trial comparing ceftazidime alone with combination antibiotic therapy in cancer patients with fever and neutropenia

To assess the efficacy of single-agent therapy relative to standard combination antibiotic therapy for the initial management of fever and neutropenia in cancer patients, we conducted a randomized trial comparing ceftazidime alone with a combination of cephalothin, gentamicin, and carbenicillin. Of 550 evaluable episodes of fever and neutropenia, 282 were treated with ceftazidime alone and 268 with the combination. All episodes were evaluated for responses at 72 hours after the start of treatment and at resolution of the neutropenia. Of the patients with unexplained fever who were given ceftazidime alone, 99 percent were alive at 72 hours and 98 percent were alive when the neutropenia resolved, as compared with 100 percent and 98 percent, respectively, of those given combination therapy. Of the patients with documented infection who were given ceftazidime alone, 98 percent were alive at 72 hours and 89 percent when the neutropenia resolved, as compared with 98 percent and 91 percent, respectively, of those given combination therapy. The majority of episodes of documented infection in both treatment groups necessitated additional antimicrobial treatment or other modifications of the initial regimen, as compared with only 22 percent of the episodes of unexplained fever. We conclude that initial single-agent therapy with certain beta-lactam antibiotics is a safe alternative to standard combination antibiotic therapy, although patients with documented infection or protracted neutropenia are likely to require additional or modified treatment.