Infections in the Cancer Patient
Clinical Snapshot
Cancer patients are more susceptible to infection than the general population because the malignancy itself and its treatment damage multiple layers of host defense simultaneously — neutrophil number and function, mucosal barriers (severe chemotherapy- or radiation-induced mucositis lets colonizing oral and gut flora translocate into the bloodstream), humoral (B-cell/antibody) immunity, and cell-mediated (T-cell) immunity.[1] Febrile neutropenia is a medical emergency: because these patients cannot mount a normal inflammatory response, fever is frequently the only sign of a serious infection, and the inability to reliably distinguish an infected from a non-infected neutropenic patient at presentation is exactly why empiric broad-spectrum IV antibiotics are started immediately rather than after a source is found.[1] This chapter covers febrile neutropenia risk stratification and empiric antibacterial therapy, empiric and prophylactic antifungal and antiviral therapy, colony-stimulating factor use, central-line-associated bloodstream infection, and vaccination considerations in immunosuppressed cancer patients — the areas where a pharmacist's dosing, timing, and de-escalation input most directly affects outcomes.
Recognize the Condition
Fever is often the only sign
Neoplasms themselves can occasionally cause fever, but an infectious cause must be sought and presumptively treated in every febrile cancer patient — the diagnosis is never assumed to be "tumor fever" at first presentation.[1] Fever is defined as a single oral temperature of 38.3°C or higher, or a temperature of 38.0°C or higher sustained for at least 1 hour, in the absence of an obvious environmental cause.[1] Neutropenia is defined as an absolute neutrophil count (ANC) of 0.5 ×10⁹/L or lower; profound neutropenia — an ANC under 0.1 ×10⁹/L — confers substantially greater infection risk, and risk rises further the longer neutropenia persists, with neutropenia expected to last more than 7 days considered higher risk than neutropenia expected to resolve within 7 days.[1]
Where infection typically originates
Most infections arise from organisms that already colonize the patient at or near the site of infection — skin, oropharynx, GI tract, lungs, or genitourinary tract — rather than from a new environmental exposure. Bacteria are the most common documented pathogens in febrile neutropenic episodes, though in most episodes no organism is ever identified.[1] Local antimicrobial resistance patterns matter directly to empiric drug selection — actively consider the possibility of MRSA, vancomycin-resistant enterococci (VRE), extended-spectrum beta-lactamase (ESBL)-producing Enterobacterales, carbapenem-resistant Enterobacterales, and Candida auris colonization or infection when choosing and escalating therapy.[1]
Site-specific clues to actively seek
Because classic localizing signs (pus, an infiltrate, urinary symptoms) can be blunted or absent in a neutropenic patient, actively examine and ask about: the oral cavity and pharynx (mucositis, thrush), venous catheter exit sites and tunnels, skin and perianal area (visual inspection only — see Common Errors below), sinuses, chest, and any area of localized pain, swelling, or new neurologic change.[1]
Risk Factors
- Depth of neutropenia — profound neutropenia (ANC under 0.1 ×10⁹/L) carries substantially higher infection risk than moderate neutropenia.
- Duration of neutropenia — neutropenia lasting more than 7 days carries substantially higher risk than neutropenia expected to resolve within 7 days.
- Mucosal barrier injury (oral or GI mucositis) from cytotoxic chemotherapy or radiation, allowing colonizing organisms to translocate into the bloodstream.
- Central venous catheters, implanted ports, and other indwelling devices.
- Humoral immune defects (B-cell/antibody dysfunction) — e.g., chronic lymphocytic leukemia, multiple myeloma, hypogammaglobulinemia.
- Cell-mediated immune defects (T-cell dysfunction) — e.g., lymphoma, prolonged corticosteroid therapy, purine-analogue chemotherapy, alemtuzumab, graft-versus-host disease and its immunosuppressive treatment, allogeneic hematopoietic stem-cell transplantation.
- Functional or anatomic asplenia (splenectomy) — markedly increased risk of overwhelming infection with encapsulated organisms.
- Tumor obstruction of a natural body passage (bronchus, bowel, ureter, biliary tree), impairing normal clearance and predisposing to local infection.
- Malnutrition and poor performance status.
- A prior invasive fungal infection, particularly in a patient who will become neutropenic again.
- Known colonization with a multidrug-resistant organism.
- Extended hospitalization and recent broad-spectrum antibiotic exposure.
Red Flags & Refer
Febrile neutropenia is itself the red flag — this is a medical emergency requiring immediate empiric IV antibiotics; there is no "watch and wait" version of this presentation.
- ANC 0.5 ×10⁹/L or lower with a fever of 38.3°C or higher (single reading), or 38.0°C or higher sustained for at least 1 hour — start empiric IV antibiotics within 1 hour; do not wait for culture results or full workup completion.[1]
- Signs of sepsis or hemodynamic instability — hypotension, marked tachycardia, altered mental status, tachypnea, mottled skin, or reduced urine output.
- Signs of a central-line-associated bloodstream infection — rigors during or after catheter access/flushing, erythema, purulence, or tenderness at the exit site or along the tunnel, or bacteremia without another identified source.
- New focal neurologic signs, severe headache, or meningismus, suggesting a CNS infection.
- Severe mucositis preventing oral intake, or severe abdominal pain/distension in a profoundly neutropenic patient (possible neutropenic enterocolitis).
- Any suspicion of invasive fungal infection in a high-risk neutropenic patient — fever persisting despite appropriate broad-spectrum antibiotics, a new pulmonary infiltrate, or sinus pain with a necrotic lesion.
- Rapidly spreading skin or soft-tissue infection, or any finding suggesting a necrotizing infection.
Assessment & Diagnosis
History
- History of significant infections and drug allergy/sensitivity, including the specific nature of any prior reaction.
- The nature of the malignancy and its associated host-defense defects (e.g., neutropenia, B-cell and/or T-cell dysfunction).
- The impact of cytotoxic, myelosuppressive, or immunosuppressive therapy — note the day of fever onset relative to the first day of the most recent chemotherapy cycle.
- Neutropenia severity and expected duration, since these are the main predisposing factors for infection.
- Prior iatrogenic procedures — splenectomy, venous access device placement, or other surgery.
- Whether the malignancy could be obstructing a natural body passage (bronchus, bowel, ureter, biliary tree).
- CNS dysfunction — changes in cranial nerve function, strength, coordination, stance/gait, sensation, or mental status.
- Occupational and travel history, and animal exposure.
Physical examination
Complete exam with particular attention to venous access sites, wounds, skin, mouth, pharynx, sinuses, chest, and other possible sites of infection; note any localizing signs — shortness of breath, localized pain, facial or extremity swelling, mental status change, seizures, or focal weakness suggesting a CNS infection. Avoid digital rectal examination and rectal thermometers in a neutropenic patient — mucosal trauma can seed bacteremia; visual perianal inspection only.[1]
Investigations
- CBC with differential to assess the ANC.
- Biochemical profile with attention to renal and hepatic function.
- At least 2 sets of blood cultures — from a peripheral site and from every lumen of any venous access device.
- Culture of any other suspected site of infection (urine, skin, sputum).
- Radiographic studies appropriate to the suspected site — e.g., chest x-ray or CT for pneumonia, abdominal CT for an intra-abdominal focus, CT/MRI of the extremities for suspected soft-tissue infection, or CT/MRI of the head for suspected encephalitis, meningitis, or cerebral abscess.
- Stool testing for Clostridioides difficile and other pathogens (Salmonella, Shigella, Campylobacter, viruses, protozoa) if diarrhea is present — note that immunotherapy-related colitis can also cause diarrhea and should be considered in the differential.
- Serologic or quantitative PCR testing (adenovirus, cytomegalovirus, Cryptococcus, Epstein-Barr virus, hepatitis, human herpesviruses, respiratory viruses including SARS-CoV-2, Toxoplasma) when clinically indicated.
- Biopsy for pathology and culture of skin lesions or other suspected infectious sources (sinuses, nose, lung, GI tract) when appropriate.
Diagnosing central-line-associated bloodstream infection
Whenever catheter infection is suspected, draw paired blood cultures — one set from a peripheral vein and one set from every catheter lumen — before changing antimicrobial therapy. Growth of the same organism from the catheter-drawn sample at least 2 hours before the peripheral sample turns positive (differential time to positivity) supports a catheter source.[2]
Risk stratification — which patients can be treated as outpatients
The MASCC (Multinational Association for Supportive Care in Cancer) risk index is a validated, published point-sum used to identify febrile neutropenic patients at low risk for serious complications.[3] Every criterion below is scored independently and the points are summed.
| Criterion | Points |
|---|---|
| Burden of illness: no or mild symptoms | 5 |
| Burden of illness: moderate symptoms | 3 |
| Burden of illness: severe symptoms | 0 |
| No hypotension (systolic blood pressure over 90 mmHg) | 5 |
| No chronic obstructive pulmonary disease | 4 |
| Solid tumor, or a hematologic malignancy with no prior invasive fungal infection | 4 |
| No dehydration requiring parenteral fluids | 3 |
| Outpatient status at the onset of fever | 3 |
| Age under 60 years | 2 |
Maximum possible score is 26. A score of 21 points or higher identifies a patient as low risk for serious complications; a score under 21 identifies high risk, favoring inpatient IV therapy.[3][4]
On a live calculator: the MASCC index is a genuine, fixed, published point-sum, not a continuously-weighted regression model like GRACE, so it is a reasonable future calculator candidate in principle. However, its "burden of illness" item assigns three different point values (5, 3, or 0) to three graded symptom levels rather than a simple present/absent toggle — a design the site's current checkbox-only calculator pattern (built for the TIMI score) cannot represent without adding a new multi-option control type. This chapter therefore ships the teaching table above for manual scoring rather than a live calculator; the underlying MASCC score itself is not disqualified the way GRACE is.
Meeting the MASCC threshold alone is not sufficient to send a patient home — outpatient management also requires the specific clinical and logistic criteria described in Choose Initial Treatment below.[4]
Low-risk vs. high-risk febrile neutropenia treatment tracks
Low-risk track
MASCC score 21 or higher, ANC expected to recover within 7 days, no significant medical comorbidity, and reliable access to prompt reassessment — oral outpatient antibiotic therapy is an option (see Choose Initial Treatment).[4]
High-risk track
MASCC score under 21, or the clinical/logistic criteria for outpatient management are not met — inpatient IV antipseudomonal beta-lactam monotherapy is required, with vancomycin added only for a specific indication (see Choose Initial Treatment).[1]
Treatment Targets
- Recognize and treat infection immediately in a febrile neutropenic patient, since infected and non-infected neutropenic patients cannot be reliably distinguished at presentation.
- Cover both gram-positive and gram-negative pathogens, with reliable antipseudomonal activity, from the very first dose.
- Achieve time-to-first-antibiotic-dose within 1 hour of a suspected febrile neutropenic episode.
- Identify low-risk patients who can safely step down to oral or outpatient therapy, and high-risk patients who need continued inpatient IV therapy.
- Add antifungal coverage promptly when fever persists despite appropriate broad-spectrum antibacterial therapy.
- Prevent febrile neutropenia in future chemotherapy cycles for patients at meaningfully elevated risk, using colony-stimulating factors and/or antimicrobial prophylaxis.
- Recognize and manage central-line-associated bloodstream infection promptly, including the decision to remove or salvage the catheter.
- Protect immunosuppressed patients from vaccine-preventable disease without exposing them to live-vaccine risk during immunosuppression.
Choose Initial Treatment
Time to antibiotics
Any patient with febrile neutropenia needs the first dose of empiric IV antibiotics within 1 hour of presentation. Draw at least 2 sets of blood cultures — a peripheral sample and every catheter lumen — immediately beforehand, but do not delay antibiotics for culture results or a completed workup.[1]
Empiric antibacterial regimen — high-risk / inpatient
1st line monotherapy with an IV antipseudomonal beta-lactam — piperacillin/tazobactam, cefepime, meropenem, or imipenem/cilastatin — provides adequate first-line gram-negative and gram-positive coverage without routinely adding an aminoglycoside or vancomycin.[1][5]
Add vancomycin only for a specific indication: suspected catheter-related infection, skin/soft-tissue infection, pneumonia, hemodynamic instability, known MRSA colonization, severe mucositis, or a blood culture growing gram-positive cocci pending identification — not as a routine addition to every regimen.[1]
Add an aminoglycoside or a fluoroquinolone only for a specific concern — suspected resistant gram-negative organism, septic shock pending susceptibilities, or a documented local resistance pattern monotherapy would not cover. Routine double gram-negative coverage adds toxicity without an outcome benefit over monotherapy for most patients.[1]
Severe (anaphylactic-type) penicillin or cephalosporin allergy — use ciprofloxacin plus vancomycin as the empiric regimen instead of a beta-lactam.[5]
Empiric therapy — low-risk / outpatient-eligible
Oral outpatient therapy — ciprofloxacin plus amoxicillin/clavulanate — is an option only when the patient meets all of: MASCC score 21 or higher, ANC expected to recover within 7 days, no significant medical comorbidity, no hepatic or renal insufficiency, and reliable access to prompt reassessment (a caregiver, transportation, and phone/return access within about 1 hour). The MASCC score alone does not make this decision.[4]
Observe the first dose and confirm early clinical stability before discharging a patient to the oral outpatient pathway; re-admit for IV therapy immediately if fever persists, new symptoms develop, or oral intake is not tolerated.[4]
Duration of antibacterial therapy
Neutropenic patient, no source identified: continue therapy until afebrile for at least 48 hours and no longer neutropenic (ANC 0.5 ×10⁹/L or higher); an early-discontinuation strategy after more than 72 hours afebrile with clinical stability is a reasonable antimicrobial-stewardship alternative even before ANC recovery, in a hemodynamically stable patient.[1]
Microbiologically or clinically documented infection: continue broad-spectrum therapy for a minimum of 10-14 days and until afebrile and no longer neutropenic (ANC 0.5 ×10⁹/L or higher) for at least 48 hours.[1]
Non-neutropenic cancer patient with suspected bacterial infection: continue therapy for approximately 7 days and until afebrile for at least 48 hours, or switch to oral therapy once stable and tolerating oral intake to complete a source-appropriate course.[1]
Persistent or recurrent fever
Reassess and add empiric antifungal therapy if fever persists 4-7 days despite appropriate broad-spectrum antibacterial therapy and no source has been identified, particularly with anticipated prolonged neutropenia.[1][5]
Non-Pharmacologic Treatment
- Standard precautions, especially hand hygiene, for every immunocompromised patient.
- High-efficiency particulate air (HEPA) filtration rooms for profoundly neutropenic patients at high risk for filamentous fungal infection (e.g., allogeneic stem-cell transplant recipients, prolonged neutropenia).
- Contact precautions for patients colonized or infected with a multidrug-resistant organism — MRSA, vancomycin-resistant enterococci, ESBL-producing Enterobacterales, carbapenem-resistant Enterobacterales, Candida auris, or C. difficile.
- Droplet precautions for respiratory viral illness.
- Airborne precautions for varicella-zoster infection and suspected tuberculosis.
- Avoid fresh flowers and plants in the rooms of neutropenic patients.
- Avoid unnecessary rectal manipulation — digital rectal exam, rectal thermometers, enemas, or suppositories — in neutropenic patients, given the mucosal-trauma bacteremia risk.
- Maintain oral hygiene and mucositis care to reduce the mucosal-barrier-injury route of infection.
- Restricting specific food types (raw fruits/vegetables, raw eggs, aged cheese) in a "low-bacterial diet" is common institutional practice, though supporting evidence is mixed — follow local policy.
Special Populations
Pregnancy
Cancer diagnosis and treatment during pregnancy needs multidisciplinary (oncology, maternal-fetal medicine, infectious diseases) management. Beta-lactams (penicillins, cephalosporins, carbapenems) and vancomycin are preferred first-line given their long safety record. Aminoglycosides are used only when no alternative exists, given a theoretical fetal ototoxicity risk, with close monitoring. Voriconazole and posaconazole are generally avoided in pregnancy given teratogenicity in animal studies; a lipid amphotericin B formulation is generally preferred for invasive fungal infection in pregnancy. Fluoroquinolones are avoided when a suitable alternative exists, but used if a serious infection specifically requires one and no alternative is adequate.
Breastfeeding
Most beta-lactams, cephalosporins, carbapenems, and vancomycin are considered compatible with breastfeeding. Aminoglycosides are largely compatible given poor oral bioavailability to the infant. Fluoroquinolones are now considered compatible by many references despite historic caution. Fluconazole is compatible; voriconazole and posaconazole have limited breastfeeding data — discuss with the treating team before use.
Pediatrics
Dosing throughout the Drug Tables below reflects standard mg/kg regimens usable across the pediatric age range unless otherwise noted. The MASCC risk index is validated in adults only — use an institutional or pediatric-specific febrile neutropenia protocol for risk-based triage decisions in children rather than applying the adult MASCC threshold.
Renal impairment
Vancomycin, aminoglycosides, and most beta-lactams are renally cleared and require dose or interval adjustment, guided by levels where applicable. Prefer oral over IV voriconazole when creatinine clearance is under 50 mL/min, given accumulation of the IV solubilizing vehicle in renal impairment; isavuconazole and posaconazole do not share this issue and are reasonable alternatives. Avoid aminoglycosides when a suitable alternative exists, particularly alongside other nephrotoxic drugs (cisplatin, cyclosporine, amphotericin B, vancomycin).
Hepatic impairment
All azole antifungals are hepatically metabolized and need monitoring; caspofungin requires dose reduction in moderate hepatic impairment, and voriconazole requires dose reduction in mild-to-moderate hepatic impairment.
Hematopoietic stem-cell transplant / graft-versus-host disease
Extended and deeper immunosuppression changes prophylaxis choices — posaconazole is preferred antifungal prophylaxis during active graft-versus-host disease treatment, and letermovir prophylaxis is specific to CMV-seropositive allogeneic transplant recipients. A structured revaccination protocol is typically needed 6-12 months post-transplant once immune reconstitution allows it.
Vaccination
Cancer patients are considered immunocompromised and should not receive live vaccines during a period of significant immunosuppression.[6] Where the treatment schedule allows planning ahead, give any needed live vaccine at least 4 weeks before starting immunosuppressive therapy, and any needed inactivated vaccine at least 2 weeks before starting it.[6] The magnitude and duration of the immune response to any vaccine may be reduced while a patient is immunosuppressed, so re-checking vaccine status and considering revaccination once immune function recovers is appropriate, particularly after hematopoietic stem-cell transplantation. Where a live-vaccine alternative exists, household and close contacts of an immunosuppressed patient should preferentially receive the inactivated option (e.g., inactivated rather than live attenuated influenza vaccine).[6]
Asplenia
Splenectomized or functionally asplenic patients face markedly increased risk of overwhelming infection with encapsulated organisms (S. pneumoniae, H. influenzae, N. meningitidis) — confirm pneumococcal, meningococcal, and H. influenzae type b vaccination status is current (using inactivated vaccines on the standard non-live-vaccine timing above), and discuss a standby-antibiotic plan for fever with the treating specialist.
Monitoring & Follow-Up
Reassess clinically and repeat vital signs per institutional protocol until afebrile and stable. Trend the ANC daily with a CBC and differential. Monitor renal function at baseline and regularly during aminoglycoside or vancomycin therapy, with trough or AUC-guided vancomycin levels per institutional protocol. Repeat blood cultures to confirm clearance of documented bacteremia, particularly for S. aureus or Candida. Reassess at 4-7 days if fever persists — add antifungal coverage and consider chest/sinus imaging if not already done. Discontinue G-CSF once the ANC recovers to 0.5 ×10⁹/L or higher when it was used to treat an established neutropenic episode; continue per-cycle prophylactic dosing when used for primary or secondary prevention. De-escalate and narrow antibiotics once culture and susceptibility results return; discontinue vancomycin if no vancomycin-susceptible organism is identified and its original indication has resolved. For a confirmed central-line-associated bloodstream infection, follow blood cultures to clearance, and arrange echocardiography for S. aureus bacteremia (to exclude endocarditis) or an ophthalmologic exam for candidemia (to exclude endophthalmitis). Reassess antimicrobial and antifungal prophylaxis needs at the start of every subsequent chemotherapy cycle, not only the first.
Common Errors to Avoid
- Delaying the first dose of empiric antibiotics to wait for a completed workup, imaging, or culture results — time-to-antibiotics within 1 hour is the priority.
- Withholding empiric antibiotics because no source is obvious — most febrile neutropenic episodes never have an identified source, and the fever itself is the indication to treat.
- Adding an aminoglycoside to a beta-lactam as routine "double coverage" — this increases toxicity without an outcome benefit over monotherapy for most patients.
- Continuing vancomycin indefinitely "just in case" once started — discontinue it if no vancomycin-susceptible organism is identified and the indication that prompted it has resolved.
- Performing a digital rectal exam, giving rectal medications, or taking a rectal temperature in a neutropenic patient — mucosal trauma can seed bacteremia.
- Reusing fluconazole empirically for persistent fever in a patient already on fluconazole prophylaxis — breakthrough fever on fluconazole suggests a resistant or mould infection and needs a different antifungal class.
- Avoiding cefepime monotherapy out of an outdated mortality concern — more recent, larger analyses have not confirmed the signal seen in some earlier data.
- Applying the MASCC score to a pediatric patient, or using the score alone to decide outpatient management without confirming the clinical/logistic criteria (reliable follow-up access, no significant comorbidity).
- Missing a central-line-associated bloodstream infection because blood cultures were drawn only peripherally, without a paired sample from every catheter lumen.
- Giving a live vaccine during a period of significant immunosuppression, or missing the window to complete a needed vaccine series before planned immunosuppressive therapy when the schedule allows it.
- Forgetting to reassess antimicrobial and antifungal prophylaxis needs at the start of every new chemotherapy cycle, not only the first.
- Combining an aminoglycoside with another nephrotoxic drug (vancomycin, amphotericin B, cisplatin, cyclosporine) without adjusting monitoring intensity.
Clinical Decision Algorithm
Drug Tables
How to use this table: Doses are adult doses and require patient-specific confirmation (renal/hepatic function, weight, allergy history). Pediatric dosing is weight-based per the current product monograph unless stated. Drug pricing is intentionally omitted. Select any drug name to open its complete Pharmasist Drug Database page.
Antipseudomonal Beta-Lactams - Empiric Monotherapy Backbone
Any one of these four agents alone provides adequate 1st-line empiric coverage for febrile neutropenia; combining two of them does not add benefit.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Piperacillin/tazobactam | Adults: 4.5 g IV Q6H Renal adjustment: Reduce dose/frequency for creatinine clearance under 40 mL/min per product labelling | Diarrhea, rash, hypersensitivity reactions, interstitial nephritis, neutropenia/thrombocytopenia with prolonged use | May increase methotrexate levels; may enhance warfarin's anticoagulant effect | 1st-line monotherapy option. |
| Cefepime | Adults: 2 g IV Q8H Renal adjustment: Reduce dose/frequency for creatinine clearance under 60 mL/min per product labelling | Rash, diarrhea, GI upset, headache, hypersensitivity reactions, seizures (particularly with renal impairment) | May enhance warfarin's anticoagulant effect | 1st-line monotherapy option; an earlier mortality signal from some analyses has not been confirmed in more recent, larger analyses. |
| Ceftazidime | Adults: 2 g IV Q8H | Rash, diarrhea, GI upset, headache, hypersensitivity reactions | May enhance warfarin's anticoagulant effect | An acceptable but now less-preferred option given weaker gram-positive activity than the other agents in this class. |
| Meropenem | Adults: 1 g IV Q8H (or 500 mg IV Q6H) | GI upset, hypersensitivity reactions, neutropenia/thrombocytopenia, seizures (high dose, renal impairment) | May significantly decrease valproic acid levels - avoid the combination if possible | 1st-line monotherapy option; preferred when ESBL-producing organism risk is elevated. |
| Imipenem/cilastatin | Adults: 500 mg IV Q6H | Diarrhea, hypersensitivity reactions, neutropenia, hemolytic anemia, thrombocytopenia, seizures (high dose, renal impairment) | May decrease valproic acid levels; seizure risk increases with concurrent ganciclovir | 1st-line monotherapy alternative. |
Aminoglycosides - Adjunct Only, Never Routine Monotherapy
Reserve for a specific concern about resistant gram-negative coverage or septic shock pending susceptibilities; adding an aminoglycoside to a beta-lactam as routine double coverage increases toxicity without improving outcomes.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Gentamicin | Adults: 5-7 mg/kg IV once daily (extended-interval regimen) | Ototoxicity (auditory/vestibular), nephrotoxicity, rare neuromuscular paralysis | Synergistic nephro/ototoxicity with vancomycin, amphotericin B, platinum-based antineoplastics, other nephrotoxic drugs | Extended-interval (once-daily) dosing is preferred; monitor levels and renal function. |
| Tobramycin | Adults: 5-7 mg/kg IV once daily (extended-interval regimen) | Ototoxicity (auditory/vestibular), nephrotoxicity, rare neuromuscular paralysis | Synergistic nephro/ototoxicity with vancomycin, amphotericin B, platinum-based antineoplastics, other nephrotoxic drugs | May be substituted for gentamicin for the same indications. |
| Amikacin | Adults: 15-20 mg/kg IV once daily (extended-interval regimen) | Ototoxicity (auditory/vestibular), nephrotoxicity, rare neuromuscular paralysis | Synergistic nephro/ototoxicity with vancomycin, amphotericin B, platinum-based antineoplastics, other nephrotoxic drugs | Reserve for suspected resistance to other aminoglycosides. |
Glycopeptides and Gram-Positive Reserve Agents
Add only for a specific gram-positive indication; discontinue if no vancomycin-susceptible organism is identified.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Vancomycin (IV) | Adults: 15-20 mg/kg IV Q8-12H, trough target 15-20 mg/L (or AUC-guided per institutional protocol) Loading dose (severe infection): 25-30 mg/kg IV once | Infusion-related flushing/hypotension (red man syndrome), nephrotoxicity, ototoxicity, phlebitis | Enhanced nephro/ototoxicity with aminoglycosides, amphotericin B, other nephrotoxic drugs | Add for suspected catheter infection, skin/soft-tissue infection, pneumonia, instability, MRSA colonization, severe mucositis, or gram-positive cocci on culture pending identification. |
| Linezolid | Adults: 600 mg PO/IV Q12H | Thrombocytopenia, anemia, leukopenia, peripheral neuropathy with prolonged use | Possible serotonin syndrome with SSRIs/MAOIs/other serotonergic drugs; may potentiate adrenergic agents | Reserve antimicrobial - use for confirmed MRSA/VRE or vancomycin intolerance. |
| Daptomycin | Adults: 4-6 mg/kg IV once daily | Elevated creatine kinase/myopathy, rash, headache, constipation | Possible increased myopathy risk with statins | Not effective for pneumonia - lung surfactant inactivates it; do not use for a suspected/confirmed respiratory source. |
Fluoroquinolones
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Ciprofloxacin | Outpatient combination therapy: 500-750 mg PO Q12H Prophylaxis: 500 mg PO Q12H during the expected neutropenic period | GI upset, rash, CNS effects, dysglycemia, QT prolongation, tendinopathy | Increases INR with warfarin; chelated by antacids/iron/calcium/sucralfate - separate dosing; avoid with Class IA/III antiarrhythmics or prolonged QT | Used for low-risk oral outpatient combination therapy, and for antibacterial prophylaxis in high-risk afebrile neutropenic patients. |
| Levofloxacin (oral/IV) | Prophylaxis: 500 mg PO/IV once daily during the expected neutropenic period Treatment: 500 mg PO/IV once daily | GI upset, tendinopathy, QT prolongation, dysglycemia, headache, insomnia | Increases INR with warfarin; chelated by antacids/iron/calcium/sucralfate - separate dosing; avoid with Class IA/III antiarrhythmics or prolonged QT | Preferred antibacterial prophylaxis agent for high-risk afebrile neutropenic patients with anticipated neutropenia lasting more than 7 days. |
Anaerobic and Adjunct Antibacterials
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Metronidazole | Adults: 500 mg IV/PO Q8-12H | GI upset, reversible neutropenia with prolonged use, rare seizures/peripheral neuropathy, metallic taste | Disulfiram-like reaction with alcohol; may enhance warfarin's anticoagulant effect | Add for suspected anaerobic infection only if the backbone regimen lacks antianaerobic activity - piperacillin/tazobactam and the carbapenems already cover anaerobes. |
| Clindamycin | Adults: 600 mg IV Q8H (or 300 mg PO Q6H for a milder infection) | Diarrhea, C. difficile-associated colitis, reversible neutropenia/thrombocytopenia, transient transaminase elevation | May enhance neuromuscular blocking agents | Alternative anaerobic/gram-positive coverage option in penicillin allergy. |
| Amoxicillin/clavulanate | Adults: 875/125 mg PO Q12H (or 500/125 mg PO Q8H) | Diarrhea, rash, hypersensitivity reactions, interstitial nephritis | May increase methotrexate levels; may enhance warfarin's anticoagulant effect | Oral component of the low-risk outpatient combination regimen with ciprofloxacin. |
Antifungal Triazoles
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Fluconazole | Prophylaxis: 400 mg PO/IV once daily Treatment (candidemia, susceptible organism): 400 mg PO/IV once daily | Nausea, headache, rash, abdominal pain | Hepatotoxicity risk with other hepatotoxic drugs; may raise cyclosporine, phenytoin, sulfonylurea, and warfarin levels - monitor | Prophylaxis in high-risk neutropenic patients with anticipated neutropenia lasting more than 7 days. If used prophylactically, do not reuse empirically for persistent fever - no mould coverage. |
| Voriconazole | Loading: 6 mg/kg IV Q12H for 2 doses Maintenance (IV): 4 mg/kg IV Q12H Maintenance (oral): 3-4 mg/kg PO Q12H, target trough 2-5 mg/L | Visual disturbances, hepatotoxicity, rash, nausea/vomiting | Numerous CYP2C19/2C9/3A4 interactions; contraindicated with strong CYP3A4 inducers (rifampin, carbamazepine, long-acting barbiturates); may raise cyclosporine/tacrolimus/sulfonylurea/warfarin levels | Preferred agent for confirmed or strongly suspected invasive aspergillosis.<cite data-reference-id="4606ccce-9d45-41c3-a0f7-e56c9a1dc9af"></cite> Oral preferred over IV when creatinine clearance is under 50 mL/min, given accumulation of the IV solubilizing vehicle. |
| Posaconazole | Prophylaxis (delayed-release tablet): 300 mg PO Q12H for 2 doses, then 300 mg once daily Refractory invasive infection: 300 mg PO/IV Q12H for 2 doses, then 300 mg once daily | Nausea, vomiting, diarrhea, headache, QT prolongation | Requires dose adjustment of cyclosporine, tacrolimus, sirolimus, statins, vinca alkaloids, midazolam | Preferred antifungal prophylaxis in acute leukemia induction chemotherapy and in graft-versus-host disease. |
| Isavuconazole | Loading: 200 mg PO/IV Q8H for 6 doses Maintenance: 200 mg PO/IV once daily | Nausea, vomiting, diarrhea, hepatotoxicity (less than voriconazole), hypokalemia | Contraindicated with strong CYP3A4/5 inducers/inhibitors | Alternative to voriconazole for invasive aspergillosis, with less hepatotoxicity.<cite data-reference-id="4606ccce-9d45-41c3-a0f7-e56c9a1dc9af"></cite> |
| Itraconazole | Adults: 200 mg PO Q12H | Nausea, rash, headache, reversible hepatic enzyme elevation, negative inotropic effect (avoid in heart failure) | Reduced absorption with H2-antagonists/PPIs; increases levels of statins, digoxin, cyclosporine, sulfonylureas, warfarin | Preferred prophylaxis for graft-versus-host disease patients at high aspergillosis risk when posaconazole is not used. |
Echinocandins
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Caspofungin | Loading: 70 mg IV once Maintenance: 50 mg IV once daily | Fever, nausea, vomiting, phlebitis at the infusion site, diarrhea, elevated liver enzymes with cyclosporine | Carbamazepine, dexamethasone, efavirenz, phenytoin, and rifampin reduce caspofungin levels; caspofungin reduces tacrolimus levels | 1st-line empiric antifungal for persistent febrile neutropenia. |
| Micafungin | Prophylaxis: 50 mg IV once daily Treatment: 100-150 mg IV once daily | Headache, rash, nausea, vomiting, phlebitis at the infusion site | Increases nifedipine and sirolimus levels | Alternative empiric/treatment agent; also used for hematopoietic stem-cell transplant antifungal prophylaxis. |
| Anidulafungin | Loading: 200 mg IV once Maintenance: 100 mg IV once daily | Diarrhea, hypokalemia, elevated liver enzymes, rash | None clinically significant | Alternative for candidemia in neutropenic or non-neutropenic patients.<cite data-reference-id="8e3ad28a-70a4-45c1-9fa8-644a13a24a0d"></cite> |
Polyenes
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Amphotericin B (liposomal) | Adults: 3-5 mg/kg IV once daily | Infusion reactions, hypokalemia, renal dysfunction (less than the conventional formulation), headache | Increased nephrotoxicity with other nephrotoxic drugs | Preferred over conventional amphotericin B deoxycholate given substantially less nephrotoxicity and fewer infusion reactions; used for documented or empiric invasive fungal infection when azole/echinocandin therapy is not suitable. |
| Amphotericin B deoxycholate (conventional) | Adults: 0.3-1.5 mg/kg IV once daily | Infusion rigors, nephrotoxicity (azotemia), hypokalemia, phlebitis, thrombocytopenia | Increased nephrotoxicity with other nephrotoxic drugs | Largely superseded by lipid formulations given substantially greater nephrotoxicity; no separate monograph in this database for the conventional formulation - confirm product-specific dosing before use. |
| Nystatin | Adults: 3.6 million units (oral suspension) Q4H PO | Nausea, vomiting, diarrhea | None significant | Oral candidiasis (swish and swallow) only - esophageal or invasive candidiasis needs a systemic agent. |
Antiviral Nucleoside Analogues - HSV/VZV
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Acyclovir | Prophylaxis: 400-800 mg PO Q8-12H Severe/disseminated disease: 5-10 mg/kg IV Q8H with adequate hydration | Phlebitis, rash, hypotension with rapid IV infusion, headache, nausea, rare tremor/confusion/seizures, renal dysfunction with inadequate hydration | Probenecid decreases renal clearance; may raise theophylline levels | Prophylaxis for HSV-seropositive patients undergoing chemotherapy for leukemia, lymphoma, or multiple myeloma, or undergoing hematopoietic stem-cell transplantation. IV route reserved for severe/disseminated disease. |
| Valacyclovir | Prophylaxis: 500 mg PO Q12H | Headache, nausea | Probenecid decreases renal clearance | Better oral bioavailability than acyclovir; alternative prophylaxis agent. |
| Famciclovir | Prophylaxis: 500 mg PO Q12H | Headache, nausea, pruritus | Probenecid decreases renal clearance | Alternative prophylaxis agent. |
Cytomegalovirus-Directed Antivirals
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Ganciclovir | Induction: 5 mg/kg IV Q12H Maintenance: 6 mg/kg IV once daily | Leukopenia, thrombocytopenia, nausea, headache, behavioural changes | Avoid with zidovudine - additive hematologic toxicity | Treatment of CMV infection/disease in hematopoietic stem-cell transplant recipients. |
| Valganciclovir | Adults: 900 mg PO once or twice daily depending on induction vs. maintenance phase | Leukopenia, thrombocytopenia, nausea, headache, behavioural changes | Avoid with zidovudine - additive hematologic toxicity | Oral prodrug of ganciclovir, used when oral therapy is appropriate. |
| Foscarnet | Acyclovir-resistant HSV: 40 mg/kg IV Q8H Ganciclovir-resistant CMV: 60 mg/kg IV Q8H, specialist-directed duration | GI upset, fever, headache, electrolyte disturbances (may cause tetany/seizures), nephrotoxicity, anemia, elevated liver enzymes, QT prolongation | Additive nephrotoxicity with acyclovir, aminoglycosides, amphotericin B, cyclosporine, tacrolimus, methotrexate; additive QT prolongation with other QT-prolonging drugs; increased seizure risk with ciprofloxacin | For acyclovir-resistant HSV/VZV or ganciclovir-resistant CMV - infectious diseases consultation recommended. |
| Letermovir | Adults: 480 mg PO/IV once daily | Nausea, vomiting, diarrhea, tachycardia, atrial fibrillation | Reduces levels of cyclosporine, ergot alkaloids, pimozide, amiodarone, and statins (especially simvastatin) - significant CYP3A interactions | Prophylaxis (not treatment) to prevent CMV infection after allogeneic hematopoietic stem-cell transplantation in a CMV-seropositive recipient.<cite data-reference-id="2276afcb-1420-40cc-a653-d96a71699943"></cite> |
| Maribavir | Adults: 400 mg PO Q12H | Taste disturbance, nausea, diarrhea, vomiting, fatigue | CYP3A4 inducers (carbamazepine, phenobarbital, phenytoin) may decrease maribavir levels | For refractory or resistant CMV infection - specialist-directed. |
Neuraminidase Inhibitor and COVID-19 Antivirals
There is no role for empiric antiviral use without evidence of specific viral disease.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Oseltamivir | Treatment: 75 mg PO Q12H | Nausea, vomiting, diarrhea, abdominal pain | None clinically significant | Mainstay for susceptible influenza in cancer patients. |
| Nirmatrelvir/ritonavir | Adults, eGFR 60 mL/min or higher: 300 mg nirmatrelvir + 100 mg ritonavir PO Q12H for 5 days Adults, eGFR 30-59 mL/min: 150 mg nirmatrelvir + 100 mg ritonavir PO Q12H for 5 days | Altered taste, elevated blood pressure, diarrhea, headache, myalgia | Numerous - ritonavir is a strong CYP3A4 inhibitor; contraindicated with strong CYP3A4 inducers - verify against a full interaction resource before every course | For COVID-19 in nonhospitalized high-risk cancer patients. |
| Remdesivir | Day 1: 200 mg IV Days 2 onward: 100 mg IV once daily | Elevated transaminases, headache, nausea, rash | Chloroquine/hydroxychloroquine may reduce antiviral effect | IV-only; for COVID-19 in hospitalized or high-risk cancer patients. |
Antimicrobial Prophylaxis - Pneumocystis jirovecii and Special Populations
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Sulfamethoxazole/trimethoprim | Prophylaxis: 1 single-strength (400/80 mg) tablet PO once daily, or 1 double-strength (800/160 mg) tablet PO 3 times weekly | Nausea, vomiting, hypersensitivity reactions (may be severe), myelosuppression, hyperkalemia | Increases phenytoin and warfarin effect; enhances methotrexate toxicity | Preferred PJP prophylaxis for patients with pronounced T-cell dysfunction - 20 mg/day or more of prednisone-equivalent for 28 days or longer, or purine-analogue therapy. |
| Dapsone | Prophylaxis: 100 mg PO once daily | Hemolytic anemia (especially with G6PD deficiency), hypersensitivity reactions, hepatotoxicity, neutropenia, thrombocytopenia | Rifampin reduces dapsone levels - avoid the combination | Alternative PJP prophylaxis when sulfamethoxazole/trimethoprim cannot be used - check G6PD status first. |
| Atovaquone | Prophylaxis: 1500 mg PO once daily | GI upset, headache, rash | Rifampin reduces atovaquone levels - avoid the combination; may enhance warfarin's anticoagulant effect | Alternative PJP prophylaxis, taken with food to improve absorption. |
| Pentamidine (inhaled) | Prophylaxis: 300 mg inhaled (nebulized) once monthly | Chest tightness, cough, dyspnea with the inhaled route | None clinically significant with the inhaled route | Alternative PJP prophylaxis for patients who cannot tolerate oral options. |
Colony-Stimulating Factors
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Filgrastim | Adults: 5 mcg/kg SC once daily, starting 24-72 hours after chemotherapy, continued through count recovery each cycle | Bone pain, injection-site reactions, rare splenic rupture, rare acute respiratory distress syndrome | None clinically significant; avoid giving within 24 hours before or after cytotoxic chemotherapy | Primary prophylaxis when the regimen's febrile-neutropenia risk is 20% or higher, or secondary prophylaxis after a prior febrile-neutropenia/dose-limiting-neutropenia event when maintaining dose intensity matters. Discontinue once ANC recovers to 0.5 x10⁹/L or higher when used to treat an established neutropenic episode.<cite data-reference-id="53dfbacb-3572-4a66-b678-5a9955174044"></cite> |
| Pegfilgrastim | Adults: 6 mg SC once, given at least 24 hours after chemotherapy (not weight-based) | Bone pain, injection-site reactions, rare splenic rupture, rare acute respiratory distress syndrome | None clinically significant; avoid giving within 24 hours before or after cytotoxic chemotherapy | Single fixed-dose alternative to daily filgrastim - one injection covers the full cycle. |
References
- Clinical Practice Guideline for the Use of Antimicrobial Agents in Neutropenic Patients with Cancer: 2010 Update by the Infectious Diseases Society of America — Clinical Infectious Diseases, Infectious Diseases Society of America (Freifeld AG, Bow EJ, Sepkowitz KA, et al.). Clin Infect Dis 2011;52(4):e56-e93
- Clinical Practice Guidelines for the Diagnosis and Management of Intravascular Catheter-Related Infection: 2009 Update by the Infectious Diseases Society of America — Clinical Infectious Diseases, Infectious Diseases Society of America (Mermel LA, Allon M, Bouza E, et al.). Clin Infect Dis 2009;49(1):1-45
- The Multinational Association for Supportive Care in Cancer Risk Index: A Multinational Scoring System for Identifying Low-Risk Febrile Neutropenic Cancer Patients — Journal of Clinical Oncology (Klastersky J, Paesmans M, Rubenstein EB, et al.). J Clin Oncol 2000;18(16):3038-3051
- Outpatient Management of Fever and Neutropenia in Adults Treated for Malignancy: American Society of Clinical Oncology and Infectious Diseases Society of America Clinical Practice Guideline Update — Journal of Clinical Oncology, American Society of Clinical Oncology / Infectious Diseases Society of America (Taplitz RA, Kennedy EB, Bow EJ, et al.). J Clin Oncol 2018;36(14):1443-1453
- Prevention and Treatment of Cancer-Related Infections, Version 3.2024, NCCN Clinical Practice Guidelines in Oncology — Journal of the National Comprehensive Cancer Network, NCCN Guidelines Panel (Baden LR, Swaminathan S, Almyroudis NG, et al.). J Natl Compr Canc Netw 2024;22(9):617-644
- Canadian Immunization Guide: Part 3 - Vaccination of Specific Populations - Immunization of Immunocompromised Persons — Public Health Agency of Canada. Canadian Immunization Guide, Part 3
- WBC Growth Factors: ASCO Guideline Update — Journal of Clinical Oncology, American Society of Clinical Oncology (Gyawali B, Bohlke K, Dickter JK, et al.). J Clin Oncol 2026;44(9):812-824
- Practice Guidelines for the Diagnosis and Management of Aspergillosis: 2016 Update by the Infectious Diseases Society of America — Clinical Infectious Diseases, Infectious Diseases Society of America (Patterson TF, Thompson GR 3rd, Denning DW, et al.). Clin Infect Dis 2016;63(4):e1-e60
- Clinical Practice Guideline for the Management of Candidiasis: 2016 Update by the Infectious Diseases Society of America — Clinical Infectious Diseases, Infectious Diseases Society of America (Pappas PG, Kauffman CA, Andes DR, et al.). Clin Infect Dis 2016;62(4):e1-e50
- Letermovir Prophylaxis for Cytomegalovirus in Hematopoietic-Cell Transplantation — New England Journal of Medicine (Marty FM, Ljungman P, Chemaly RF, et al.). N Engl J Med 2017;377(25):2433-2444
Professional reference only. Apply clinical judgment and verify patient-specific decisions against current authoritative guidance and product information.