Initial Antibiotic Therapy for Febrile Neutropenia

Patient Risk Stratification

• The Infectious Diseases Society of America recommends that high-risk febrile neutropenic patients receive empirical intravenous antibiotic therapy with a beta-lactam anti-pseudomonal agent: cefepime, carbapenem (meropenem or imipenem-cilastatin), or piperacillin-tazobactam 1, 2
• High-risk patients are defined as those with anticipated prolonged neutropenia (>7 days) and profound neutropenia (ANC <100 cells/mm³), significant medical comorbidities, or clinical symptoms such as hypotension, pneumonia, or abdominal pain 1, 2, 3
• Low-risk patients have anticipated brief neutropenia (<7 days), minimal comorbidities, and may be candidates for oral antibiotic therapy 1, 2, 3, 4

Initial Antibiotic Therapy for High-Risk Patients

• The recommended initial antibiotic regimen for high-risk patients is a single agent: cefepime, meropenem, imipenem-cilastatin, or piperacillin-tazobactam 1, 2
• Vancomycin is not recommended as part of the standard initial regimen, except in specific situations such as suspected catheter-related infection, skin or soft tissue infection, pneumonia, or hemodynamic instability 1, 2, 5
• For patients with a history of penicillin allergy, ciprofloxacin plus clindamycin or aztreonam plus vancomycin may be used as alternative regimens 1, 2

Initial Antibiotic Therapy for Low-Risk Patients

• The recommended oral antibiotic regimen for low-risk patients is ciprofloxacin plus amoxicillin-clavulanate, with alternatives including levofloxacin monotherapy or ciprofloxacin plus clindamycin 1, 2, 6
• Patients receiving fluoroquinolone prophylaxis should not receive fluoroquinolone-based empirical therapy 1, 2, 6

Evaluation and Modifications

• Initial evaluation should include complete blood count, serum creatinine, electrolytes, liver function tests, and at least two sets of blood cultures 1, 2
• Imaging studies such as chest radiography should be performed as clinically indicated 1, 2
• Antibiotic regimens should be modified based on clinical response, microbiological results, and patient stability 5, 7, 6

Duration of Therapy

• The duration of antibiotic therapy is dictated by the specific infection and site of infection, and should be continued until the patient has recovered from neutropenia (ANC >500 cells/mm³) or until clinically indicated 6, 2
• For patients with unexplained fever, antibiotic therapy should be continued until there are clear signs of marrow recovery (ANC >500 cells/mm³) or until clinically indicated 6, 2

Initial Antibiotic Selection for Febrile Neutropenia with Shock

Rationale for Antibiotic Selection

• The presence of shock in febrile neutropenia patients mandates immediate broad-spectrum coverage with an anti-pseudomonal beta-lactam agent, and meropenem is specifically supported as first-line monotherapy for high-risk febrile neutropenia, as recommended by the Infectious Diseases Society of America 8
• The American College of Physicians and the Infectious Diseases Society of America recommend considering adding vancomycin to the initial regimen in patients with hemodynamic instability, such as shock 9
• The addition of vancomycin addresses potential MRSA, catheter-related infections, and severe sepsis scenarios, with a strength of evidence level of moderate to high 9, 10

Coverage Considerations

• Meropenem provides robust coverage against Pseudomonas aeruginosa, which remains associated with 18% mortality in gram-negative bacteremia, compared to 5% for gram-positive organisms, according to the Infectious Diseases Society of America 8
• Vancomycin alone is inadequate for febrile neutropenia due to its lack of coverage of gram-negative organisms, particularly Pseudomonas aeruginosa, as stated by the Infectious Diseases Society of America 8
• Gram-negative bacteremia carries higher mortality (18%) than gram-positive (5%), emphasizing the need for broad-spectrum coverage, as reported by the Infectious Diseases Society of America 8

Antifungal Therapy

• Antifungal therapy, such as caspofungin, is reserved for persistent fever after 5-7 days of appropriate antibacterial therapy without response, as recommended by the European Society for Medical Oncology and the Infectious Diseases Society of America 11, 12
• Initial empirical therapy must address bacterial pathogens first, as 23% of febrile neutropenic episodes involve bacteremia, according to the Infectious Diseases Society of America 8

Meropenem Dosing for Empiric Treatment of Neutropenic Fever

Standard Dosing Regimen

• The Infectious Diseases Society of America recommends meropenem 1 gram intravenously every 8 hours as monotherapy for empiric treatment of neutropenic fever in high-risk patients, providing adequate anti-pseudomonal coverage 13, 14
• Meropenem is recommended as first-line monotherapy alongside cefepime, imipenem-cilastatin, or piperacillin-tazobactam for high-risk patients, with an 18% mortality rate associated with gram-negative bacteremia compared to 5% for gram-positive organisms 13, 14

Vancomycin Considerations

• The Infectious Diseases Society of America does not recommend routinely adding vancomycin to meropenem for initial empiric therapy unless specific indications are present, such as suspected catheter-related infection or skin/soft tissue infection 13, 14
• Vancomycin should be added only for suspected catheter-related infection, skin/soft tissue infection, hemodynamic instability, or known colonization with resistant gram-positive organisms, and discontinued after 24-48 hours if no gram-positive infection is identified 14, 15, 16

Special Clinical Scenarios

• For neutropenic enterocolitis (typhlitis), meropenem or imipenem-cilastatin with anti-pseudomonal activity is recommended as part of conservative management, according to the European Society for Medical Oncology 17

Duration and Monitoring

• The Infectious Diseases Society of America recommends continuing meropenem until ANC recovery to >500 cells/mm³ or until clinically indicated based on documented infection, with a median time to defervescence of 5 days in hematologic malignancy patients and 2 days in solid tumor patients 15
• Persistent fever alone in a stable patient does not mandate changing antibiotics; reassess at 2-4 days, according to the Infectious Diseases Society of America 14, 15

Antibiotic De-escalation Based on Culture Results

Rationale for Discontinuing Vancomycin

• Vancomycin is not indicated as part of standard empirical therapy for febrile neutropenia and should be discontinued within 24-48 hours if no gram-positive infection is identified, as recommended by the Infectious Diseases Society of America 18
• The American College of Clinical Pharmacy suggests that continuing vancomycin unnecessarily increases risks of nephrotoxicity, drug-induced neutropenia, and selection of resistant organisms 18

Rationale for De-escalating Cefepime

• The Infectious Diseases Society of America guidelines recommend de-escalating to first or second-generation cephalosporins for Proteus mirabilis once susceptibility results are available, with a strength of evidence rated as strong 19
• The European Society of Clinical Microbiology and Infectious Diseases recommends switching from cefepime to ceftriaxone 1-2g IV daily for targeted therapy of pan-sensitive Proteus mirabilis complicated UTI, with a moderate level of evidence 19

Recommended Antibiotic Adjustment

• The American College of Clinical Pharmacy recommends alternative options including ampicillin 2g IV every 6 hours or ciprofloxacin 400mg IV every 12 hours, with a high level of evidence for ciprofloxacin 19, 20
• The Infectious Diseases Society of America suggests that the total duration of antibiotic therapy should be 7-10 days for complicated UTI with associated bacteremia, with a moderate level of evidence 19

Clinical Monitoring

• The American College of Emergency Physicians recommends monitoring for clinical improvement, including defervescence, resolution of urinary symptoms, and decreasing WBC, over the next 48-72 hours, with a high level of evidence 21, 22
• The Infectious Diseases Society of America suggests that if the patient remains febrile beyond 3-5 days despite targeted therapy, reassess for occult abscess or complicated pyelonephritis requiring imaging, with a moderate level of evidence 21

Empiric Antibiotic Management for Febrile Neutropenia

Immediate Antibiotic Initiation

• Initiate intravenous anti‑pseudomonal β‑lactam therapy within 1 hour of fever onset in neutropenic patients; delays are associated with markedly higher mortality from gram‑negative bacteremia (≈ 18 % vs 5 % for gram‑positive infections)【23】【24】.
• Recommended first‑line monotherapy agents (all provide anti‑pseudomonal coverage): cefepime 2 g IV q8 h, meropenem 1 g IV q8 h, imipenem‑cilastatin, or piperacillin‑tazobactam【24】.
• Anti‑pseudomonal β‑lactams are essential because Pseudomonas aeruginosa bacteremia carries a high mortality risk in neutropenic patients【24】.

Vancomycin Use

• Routine addition of vancomycin is not recommended for initial empiric therapy【24】.
• Vancomycin should be added only when high‑risk features are present, such as:

Combination Therapy with Aminoglycosides

• Aminoglycoside‑containing combination therapy is not recommended routinely; β‑lactam monotherapy yields comparable survival with fewer adverse events【24】.
• Combination (β‑lactam + aminoglycoside) may be considered in specific situations:

Antifungal Therapy Timing

• Empiric antifungal therapy should not be started immediately in febrile neutropenia【27】.
• Add a mold‑active antifungal (e.g., voriconazole or liposomal amphotericin B) when any of the following occur:

Reassessment and Therapeutic Modification

• Reassess clinical response at 48–72 hours:
• Modify antibiotics based on culture results and clinical response, narrowing the spectrum once a pathogen is identified【23】【24】.

Duration of Antimicrobial Therapy

• Continue antibiotics until all of the following are met:

Critical Pitfalls to Avoid

• Never delay antibiotic initiation; gram‑negative bacteremia can become fatal within hours【25】.
• Avoid ceftazidime monotherapy because of limited gram‑positive activity and declining efficacy against gram‑negative organisms【24】.
• Do not use aminoglycoside monotherapy; rapid emergence of resistance is common【24】.

Assessment and Management of Fever in Hospitalized Lymphoma Patients

Immediate Evaluation (Within 1 Hour)

• Prompt evaluation and empiric broad‑spectrum antibiotics must be started within 1–2 hours of fever onset (≥ 38 °C) in all hospitalized lymphoma patients; delays significantly increase mortality from gram‑negative bacteremia. 28

Risk Stratification

• High‑risk features – anticipated prolonged neutropenia (> 7 days), profound neutropenia (ANC < 100 cells/mm³), hemodynamic instability, pneumonia, abdominal pain, or serious comorbidities. 28
• Low‑risk features – anticipated brief neutropenia (< 7 days), ANC > 100 cells/mm³, hemodynamic stability, minimal symptoms, and absence of serious comorbidities. [28][29]
• A MASCC score ≥ 21 identifies low‑risk patients; the score incorporates burden of illness, blood pressure, COPD, tumor type, hydration status, outpatient status, and age. 29

Essential Initial Diagnostic Work‑up (Before or Immediately After Antibiotics)

• Obtain two sets of blood cultures (one peripheral, one from any central line) to allow differential time‑to‑positivity for catheter‑related infection. [28][29]
• Perform a complete blood count with differential to document the absolute neutrophil count. 28
• Acquire a chest radiograph when respiratory symptoms are present. [28][30]
• Conduct urinalysis and urine culture if urinary symptoms or an indwelling catheter are present. 28
• Order stool C. difficile testing when diarrhea is reported. 30
• Perform a focused physical examination of catheter sites, skin/soft tissue, oropharynx, lungs, abdomen, and perirectal area. 28

Empiric Antibiotic Strategy for High‑Risk Patients

• Initiate IV anti‑pseudomonal β‑lactam monotherapy (e.g., cefepime, meropenem, imipenem‑cilastatin, or piperacillin‑tazobactam) immediately. (Guideline recommendation; strength of evidence not specified).

Vancomycin Use

• Routine addition of vancomycin is not recommended to the initial empiric regimen. [28][31]
• Add vancomycin only when any of the following high‑risk features are present:
  
  • Suspected catheter‑related infection (erythema/tenderness at the site). [28][31]29
  • Documented skin or soft‑tissue infection. 28
  • Pneumonia with concern for MRSA.
  • Hemodynamic instability or septic shock. [28][31]
  • Known colonization with MRSA or VRE.
• If vancomycin is started empirically, discontinue after 48 hours when blood cultures show no gram‑positive organisms. 31

Reassessment at 48–72 Hours

• Persistent fever alone in a clinically stable patient does NOT require a change in antibiotics. Median time to defervescence is ≈ 5 days in hematologic malignancies. [28][31]30
• When the patient remains febrile but stable:
  
  • Continue the initial antibiotic regimen. [28][31]
  • Repeat blood cultures to rule out new bacteremia. 30
  • Obtain chest CT if high‑risk features suggest occult fungal infection. 30
  • Obtain abdominal CT for abdominal pain or diarrhea to evaluate neutropenic enterocolitis. 30
  • Consider non‑infectious etiologies (drug fever, thrombophlebitis, disease progression, hematoma resorption). 30
• If the patient deteriorates (hemodynamic decline, organ dysfunction):
  
  • Broaden antimicrobial coverage to include resistant gram‑negative, gram‑positive, and anaerobic organisms. 31
  • Add vancomycin if not already administered. 31
  • Consider empiric antifungal therapy when fever persists 4–7 days despite appropriate antibacterials. 28

Antifungal Therapy

• Do not start empiric antifungal agents immediately.
• Add mold‑active antifungal (voriconazole, liposomal amphotericin B, or caspofungin) when any of the following occur:
  
  • Fever persists after 4–7 days of adequate antibacterial therapy. 28
  • New pulmonary infiltrates suggestive of invasive fungal infection.
  • Persistent profound neutropenia (> 7–10 days).

Duration of Antibiotic Therapy

• Continue antibiotics until all of the following are achieved:
  
  • ANC > 500 cells/mm³. [28][31]
  • Afebrile for ≥ 48 hours.
  • Documented infection adequately treated (generally 7–10 days).
• For unexplained fever in a stable patient, antibiotics may be maintained until neutrophil recovery even if fever persists. 31

Critical Pitfalls to Avoid

• Never delay antibiotic initiation beyond 1–2 hours; gram‑negative bacteremia can be rapidly fatal. 28
• Do not add vancomycin reflexively for persistent fever without evidence of gram‑positive infection. [31][30]
• Do not switch antibiotics solely on the basis of persistent fever in a clinically stable patient. [28][31]30
• Do not overlook non‑neutropenic fever in lymphoma patients, which carries higher mortality than febrile neutropenia.
• Do not miss Pneumocystis jirovecii pneumonia in lymphoma patients with interstitial infiltrates, even when the pathogen is not yet identified.

Empirical Combination Therapy and Escalation of Coverage in Febrile Neutropenia

Combination Therapy for Documented Pseudomonas aeruginosa Bacteremia

Escalation of Antimicrobial Coverage When Clinical Deterioration Occurs

Empirical Antibiotic Management for Community‑Onset Urinary Sepsis in Neutropenic Patients

Pathogen‑directed β‑lactam selection

• First‑ and second‑generation cephalosporins lack activity against the Enterobacterales that most commonly cause urinary infections and peritonitis; therefore they should be avoided in neutropenic patients with suspected urinary sepsis. 34

Vancomycin – when to add

• Routine inclusion of vancomycin in the initial empirical regimen for febrile neutropenia is not recommended. 35
• Vancomycin should be added only when the patient presents with hemodynamic instability or septic shock at the time of evaluation. 35

Aminoglycoside – when to consider

• Adding an aminoglycoside (e.g., amikacin or gentamicin) is not recommended routinely; it should be considered only in the following high‑risk situations:
  
  • The patient is in septic shock on presentation. 35
  • There is suspected bacteremia caused by multidrug‑resistant gram‑negative organisms such as Pseudomonas or Acinetobacter. 35
  • The patient has deep, persistent neutropenia with a suspected gram‑negative bacteremia. 35

Combined regimen for septic shock or hemodynamic instability

• In neutropenic patients who are hemodynamically unstable or in septic shock, the recommended empirical regimen includes:
  
  • Meropenem (broad‑spectrum β‑lactam) plus vancomycin (for high‑risk gram‑positive coverage), and consideration of an aminoglycoside for additional gram‑negative coverage. 35

Evidence level for the above recommendations was not explicitly stated in the cited sources.

Antibiotic Coverage Strategies for Bacteremic Pancytopenia

Initial Empiric Therapy

• In pancytopenic patients with bacteremic urinary‑tract infection, administer an anti‑pseudomonal β‑lactam together with an aminoglycoside within 1 hour of presentation; add vancomycin only when the patient is hemodynamically unstable or when a catheter‑related infection is suspected. [36][37]

Recommended β‑lactam + Aminoglycoside Regimens for High‑Risk Patients

• Cefepime‑based regimen: Cefepime 2 g IV every 8 h plus an aminoglycoside (gentamicin or tobramycin) is an accepted anti‑pseudomonal combination for patients with profound neutropenia (ANC < 100 cells/mm³) or prolonged neutropenia (> 7 days). 36
• Imipenem‑cilastatin‑based regimen: Imipenem‑cilastatin 1 g IV every 8 h plus an aminoglycoside provides comparable coverage against gram‑negative bacilli, including ESBL‑producing organisms. 36

Clinical Benefit of Combination Therapy

• Adding an aminoglycoside to an anti‑pseudomonal β‑lactam raises the clinical improvement rate to roughly 85 % versus 50 % with β‑lactam monotherapy in documented Pseudomonas aeruginosa infections. 38

Indications for Vancomycin

• Vancomycin should not be used routinely; it is indicated only in the following situations:
• If vancomycin is started empirically, discontinue it after 48 hours when blood cultures are negative for gram‑positive organisms. 38

De‑escalation Based on Microbiology

• Re‑evaluate antimicrobial therapy 24–72 hours after initiation and adjust according to culture and susceptibility results.

Special Considerations for Severe Granulocytopenia

• Patients with deep granulocytopenia (ANC < 100 cells/mm³) who remain febrile after 4–7 days of appropriate antibacterial therapy have an increased risk of disseminated fungal infection; empirical addition of amphotericin B should be considered. [38][37]

Monotherapy Eligibility in Low‑Risk Patients

• Monotherapy with a single anti‑pseudomonal agent is acceptable only for low‑risk neutropenic patients (anticipated neutropenia < 7 days, ANC > 100 cells/mm³, hemodynamically stable). This approach is not appropriate for pancytopenic patients with documented bacteremia. [36][37]

Management of Febrile Neutropenia – Evidence‑Based Recommendations

Immediate Action (Within 1 Hour)

• Start empiric anti‑pseudomonal β‑lactam IV therapy within one hour of fever onset in any patient with an absolute neutrophil count (ANC) < 500 cells/µL; delays are linked to an 18 % mortality from gram‑negative bacteremia. [39][40]

Pre‑Antibiotic Diagnostic Work‑up

• Obtain two sets of blood cultures – one from a peripheral vein and one from each lumen of any indwelling central venous catheter. 40
• Perform baseline laboratory tests: complete blood count with differential, serum creatinine, electrolytes, hepatic transaminases, and total bilirubin. 40
• If respiratory symptoms are present, obtain a chest radiograph. 40
• Collect cultures from other suspected infection sites (e.g., urine when dysuria or catheter present, stool when diarrhea). 40

Risk Stratification (MASCC Score)

• Apply the Multinational Association for Supportive Care in Cancer (MASCC) scoring system to decide treatment setting and intensity. 40

High‑Risk Features (Require inpatient IV therapy)

• Anticipated prolonged neutropenia > 7 days or profound neutropenia (ANC < 100 cells/µL). [39][40]
• Hemodynamic instability (hypotension or septic shock). [39][40]
• Radiographically documented pneumonia. 40
• New‑onset abdominal pain or neurologic change. 40
• Significant comorbidities (e.g., chronic obstructive pulmonary disease, heart failure, renal insufficiency). 40
• MASCC score < 21. 40

Low‑Risk Features (Candidates for outpatient oral therapy)

• Anticipated neutropenia < 7 days. [39][40]
• Hemodynamic stability with minimal symptoms. 40
• MASCC score ≥ 21. 40

Empiric Antibiotic Selection

High‑Risk Patients – IV Monotherapy (Anti‑pseudomonal β‑lactams)

• Preferred agents (choose one): meropenem 1 g IV q8 h, imipenem‑cilastatin 500 mg IV q6 h, piperacillin‑tazobactam 4.5 g IV q6 h, or cefepime 2 g IV q8 h (use only when local resistance patterns allow). [39][40]
• Reserve carbapenems for settings with high rates of extended‑spectrum β‑lactamase (ESBL)–producing organisms or after failure of other agents. 39

Low‑Risk Patients – Oral Regimen

• Ciprofloxacin 500–750 mg PO q12 h + amoxicillin‑clavulanate 875 mg PO q12 h is the recommended outpatient regimen. [39][40]
• Alternative regimens (less studied): levofloxacin 750 mg PO daily monotherapy or ciprofloxacin + clindamycin. 39
• Fluoroquinolone‑based empiric therapy must not be used in patients already receiving fluoroquinolone prophylaxis. 39
• Administer the first oral dose in a clinic or hospital; transition to outpatient care only after the patient remains clinically stable. 39

Penicillin‑Allergic Patients

• For immediate‑type hypersensitivity (e.g., hives, bronchospasm, anaphylaxis): use ciprofloxacin + clindamycin or aztreonam + vancomycin. 39
• Patients with non‑immediate‑type penicillin allergy generally tolerate cephalosporins and carbapenems. 39

Vancomycin – Indications & De‑escalation

• Vancomycin is not part of the standard initial empiric regimen. [39][40]
• Add vancomycin (15–20 mg/kg IV q8–12 h) only when any of the following are present:
  
  • Hemodynamic instability or septic shock. 39
  • Suspected catheter‑related bloodstream infection (erythema, tenderness, or purulence at catheter site). [39][40]
  • Skin/soft‑tissue infection with cellulitis. [39][40]
  • Pneumonia on imaging with concern for MRSA. 39
  • Known MRSA or VRE colonization or treatment in a hospital with high endemic rates. 39
• Discontinue vancomycin after 24–48 h if blood cultures remain negative for gram‑positive organisms, to avoid nephrotoxicity and resistance selection. 39

Aminoglycoside Combination – Restricted Use

• Add an aminoglycoside (gentamicin or amikacin, dosed per institutional protocol) only when:
  
  • Documented or suspected bacteremia with multidrug‑resistant gram‑negative organisms (e.g., Pseudomonas aeruginosa, Acinetobacter, ESBL‑producers, KPC‑producers).** 39

Antifungal Therapy – When to Initiate

• Do not start empiric antifungal agents at presentation.
• Add a mold‑active antifungal when any of the following occur:
  
  • Fever persists 4–7 days despite appropriate broad‑spectrum antibacterial therapy. 39
  • Persistent profound neutropenia (ANC < 100 cells/µL) for > 7–10 days. 39
• Recommended agents (selected per suspected pathogen):
  
  • Liposomal amphotericin B 3–5 mg/kg IV daily (preferred for suspected invasive aspergillosis).
  • Voriconazole IV (alternative for aspergillosis).
  • Caspofungin 70 mg IV loading then 50 mg IV daily (for candidemia or when prior azole prophylaxis used). [Citation for caspofungin] 39

Duration of Antibiotic Therapy

• Continue antibiotics until all three criteria are met:
  
  • ANC > 500 cells/µL with a rising trend. [39][40]
  • Afebrile for ≥ 48 h.
  • Complete resolution of all infection‑related signs and symptoms. [39][40]
• For documented infections (e.g., bacteremia, pneumonia, soft‑tissue infection), maintain the full standard course (typically 7–14 days) even if neutrophil recovery occurs earlier. 39
• In stable patients with unexplained fever, antibiotics may be continued until neutrophil recovery, or oral fluoroquinolone prophylaxis may be resumed after completing the appropriate treatment course. 39

Prophylaxis

• Fluoroquinolone prophylaxis (levofloxacin 500 mg PO daily or ciprofloxacin 500 mg PO twice daily) is recommended for high‑risk patients with anticipated prolonged and profound neutropenia (ANC < 100 cells/µL for > 7 days). 39
• Levofloxacin is preferred when there is an increased risk of oral‑mucositis‑related invasive viridans group streptococcal infection. 39
• Do not add a gram‑positive‑active agent (e.g., amoxicillin) to fluoroquinolone prophylaxis. 39
• Implement systematic monitoring of fluoroquinolone resistance among gram‑negative bacilli. 39
• Antibacterial prophylaxis is not routinely recommended for low‑risk patients expected to remain neutropenic < 7 days. 39

Critical Pitfalls (Safety Alerts)

• Never delay the initiation of empiric antibiotics beyond one hour; gram‑negative bacteremia can become fatal within hours. [40][41]
• Avoid routine addition of vancomycin for persistent fever without evidence of gram‑positive infection, as this does not improve outcomes and promotes resistance. [39][40]
• Do not switch antibiotics solely on the basis of persistent fever in a clinically stable patient; median time to defervescence is approximately five days in high‑risk patients. (Evidence not cited, therefore omitted).

All patient‑specific identifiers have been generalized to preserve privacy.

Prolonged Infusion of Piperacillin‑Tazobactam Enhances PK/PD Targets

Dosing Optimization

• Administer piperacillin‑tazobactam 4.5 g IV every 6 hours as a prolonged 4‑hour infusion for high‑risk febrile neutropenic patients—including those with augmented renal clearance or infections caused by organisms with MIC ≥ 8 mg/L—to markedly improve attainment of the pharmacodynamic target (100 % fT>MIC) compared with standard 30‑minute infusions. 42