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Topoisomerase I inhibitor

Irinotecan

Camptosar · Irino

Topoisomerase I inhibitor · approved 1996 · 5 references

A topoisomerase I poison whose severe diarrhea is the real threat to the kidneys.

Signature injury
Prerenal / Hemodynamic AKI
Severity
Mild
Reversibility
Reversible
Onset
Acute cholinergic diarrhea within hours of infusion; delayed diarrhea after ~24 hours and over subsequent days, with AKI following cumulative volume loss.

Signature kidney injury & incidence

Prerenal / Hemodynamic AKI.

Direct nephrotoxicity is not a recognized feature; the principal renal risk is prerenal AKI from severe early (cholinergic) and delayed diarrhea with volume depletion. Severe (grade 3-4) irinotecan toxicity, mostly diarrhea/neutropenia, occurs in roughly a quarter to a third of patients and is enriched in UGT1A1 poor metabolizers. AKI incidence specifically attributable to irinotecan is not well quantified.

Source: Hulshof et al., Eur J Hum Genet 2022

Reported injury signatures: Prerenal / Hemodynamic AKI.

Onset timing & rechallenge

Acute (~1–7 days) — Delayed diarrhea from ~24 hours and over subsequent days, with AKI following the cumulative volume loss.

Mechanism of kidney injury

Volume depletion from profuse SN-38-mediated secretory diarrhea (plus vomiting and poor intake) reduces effective circulating volume and renal perfusion, producing prerenal azotemia that can progress to ischemic ATN if uncorrected. The drug does not directly injure tubular cells at usual exposures; impaired SN-38 glucuronidation (UGT1A1*28/*6/*37) raises active-metabolite exposure and the severity of the diarrhea.

Clinical presentation

Watery diarrhea, orthostasis, decreased urine output, and rising BUN/creatinine with a high BUN:creatinine ratio and bland sediment; urine is concentrated (low FeNa) consistent with prerenal physiology. Early cholinergic syndrome (diaphoresis, cramping, lacrimation) reverses with atropine.

Management

Restore volume with IV crystalloid, control diarrhea, and hold chemotherapy until recovery. Prerenal AKI typically reverses promptly once euvolemia is restored; persistent injury warrants evaluation for ischemic ATN.

Risk factors

  • Severe or unmanaged delayed diarrhea
  • UGT1A1 poor-metabolizer genotype (*28/*28, *6, *37) - higher SN-38 exposure
  • ABCG2 c.421C>A and other transporter variants
  • Older age, baseline volume depletion, concurrent diuretics

Prevention

  • Aggressive antidiarrheal management (high-dose loperamide for delayed diarrhea; atropine for acute cholinergic symptoms)
  • Patient education and early oral/IV rehydration at first loose stools
  • Consider UGT1A1 genotyping; reduce starting dose to ~70% in confirmed poor metabolizers

Renal dose adjustment

Largely hepatic/biliary elimination, so no formal eGFR-based renal dose table — but the FDA label advises caution in renal impairment and directs not using irinotecan in patients on dialysis. UGT1A1 poor metabolizers warrant a ~30% starting-dose reduction. Caution and possible reduction in significant hepatic dysfunction (hyperbilirubinemia).

Dialyzability & ESKD dosing

Irinotecan and SN-38 are protein-bound and hepatically/biliary cleared; not effectively removed by dialysis, and the FDA label directs not using irinotecan in patients on dialysis.

Differential diagnosis

Diarrhea-driven prerenal AKI (volume signs, low FeNa, bland urine) vs C. difficile or neutropenic enterocolitis vs concurrent nephrotoxin ATN. The temporal link to delayed diarrhea and rapid reversal with fluids is characteristic.

Monitoring

  • Stool frequency and hydration status each cycle
  • Serum creatinine/BUN and electrolytes with significant diarrhea
  • CBC for neutropenia
  • UGT1A1 genotype before first dose where available

Key trials & series

  • DPWG UGT1A1-irinotecan pharmacogenetic guideline (Hulshof 2022)
  • FOLFIRINOX and FOLFIRI registrational regimens

Clinical pearls

  • Atropine treats the acute cholinergic diarrhea; loperamide treats the delayed diarrhea - they are different syndromes.
  • UGT1A1 poor metabolizers get worse diarrhea and thus more prerenal AKI; genotype-guided dose reduction helps.
  • The kidney is collateral damage from gut fluid loss - the renal-protective intervention is controlling diarrhea early.

Anticancer mechanism

Prodrug converted by carboxylesterases (CES1/CES2) to the active metabolite SN-38, which stabilizes the topoisomerase I-DNA cleavable complex, causing lethal double-strand breaks during DNA replication. Used in colorectal, pancreatic, and other gastrointestinal cancers (FOLFIRI, FOLFIRINOX).

Note

Kidney injury is essentially diarrhea-driven and prerenal; preventing and treating diarrhea is the key renal-protective step.

Guidelines & consensus

Each recommendation below is this atlas's faithful summary of the source, not a quotation from it — follow the PubMed link for the wording the society published. Summaries may be superseded; consult the current full text and individualize to the patient.

  • ADQI (2026) — The nephrotoxic effects of anti-cancer therapies: consensus report of the 34th Acute Disease Quality Initiative workgroupProvides expert-based statements (modified Delphi) on preventing and managing cisplatin/platinum-associated AKI, including isotonic IV hydration, attention to volume status and concomitant nephrotoxins, and incorporates evidence that IV magnesium supplementation may reduce cisplatin-associated AKI; emphasizes risk stratification and standardized AKI definitions.Nat Rev Nephrol · PMID 41361704
  • SIRM (2022) — SIRM-SIN-AIOM: appropriateness criteria for evaluation and prevention of renal damage in the patient undergoing contrast medium examinations-consensus statements from Italian College of Radiology (SIRM), Italian College of Nephrology (SIN) and Italian Association of Medical Oncology (AIOM)Recommends eGFR-based renal risk assessment and pre/post-contrast isotonic saline or sodium bicarbonate hydration; advises maintaining a 5-7 day interval between iodinated contrast administration and cisplatin in cancer patients to reduce additive nephrotoxicity.Radiol Med · PMID 35303246
  • KDIGO (2020) — KDIGO Controversies Conference on onco-nephrology: understanding kidney impairment and solid-organ malignancies, and managing kidney cancerIdentifies platinum compounds (especially cisplatin) as leading cytotoxic causes of acute tubular injury, AKI, and electrolyte/magnesium wasting; calls for interdisciplinary onco-nephrology care, accurate GFR estimation, and individualized drug dosing in patients with reduced kidney function.Kidney Int · PMID 33126977
  • KDIGO (2020) — KDIGO Controversies Conference on onco-nephrology: kidney disease in hematological malignancies and the burden of cancer after kidney transplantationAddresses chemotherapy-associated AKI/CKD in hematologic cancer, GFR estimation and chemotherapy dosing in patients with reduced kidney function, and management priorities and research gaps for onco-nephrology care.Kidney Int · PMID 33276867
  • ADDIKD (2025) — Integrating International Consensus Guidelines for Anticancer Drug Dosing in Kidney Dysfunction (ADDIKD) into everyday practiceProvides GRADE-based, drug-specific dose-adjustment recommendations for anticancer agents in kidney dysfunction (illustrated for methotrexate, cisplatin, carboplatin and nivolumab); the recommendations build on Part 1's standardised CKD-EPI eGFR assessment rather than Cockcroft-Gault creatinine clearance.EClinicalMedicine · PMID 40290844
  • ADDIKD (2025) — Aligning kidney function assessment in patients with cancer to global practices in internal medicineThree consensus recommendations: assess kidney function by GFR (measured GFR or CKD-EPI eGFR), classify it using KDIGO categories, and use this uniform approach to dose anticancer drugs — moving cancer medicine away from Cockcroft-Gault estimated creatinine clearance.EClinicalMedicine · PMID 40290845
  • ADDIKD (2025) — A methodology for determining dosing recommendations for anticancer drugs in patients with reduced kidney functionEstablishes that, where RCT evidence is lacking, anticancer drug dosing recommendations in kidney dysfunction should be derived by critically appraising observational literature via GRADE combined with structured international multidisciplinary consensus voting.EClinicalMedicine · PMID 40290846
  • KDIGO (2013) — Diagnosis, evaluation, and management of acute kidney injury: a KDIGO summary (Part 1)Defines/stages AKI by serum creatinine and urine output; emphasizes avoiding nephrotoxins, maintaining euvolemia/perfusion, dose-adjusting drugs to kidney function, and monitoring high-risk patients — the framework applied to nephrotoxic anti-cancer agents.Crit Care · PMID 23394211
  • KDIGO (2024) — Executive summary of the KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease: known knowns and known unknownsEvaluate and risk-stratify CKD, manage to delay progression and its complications, and practise explicit medication management and drug stewardship — the framework the atlas's G1–G5 eGFR banding and every renal dose-adjustment recommendation sit inside. Because the guideline excludes dialysis and transplant recipients by its own statement of scope, its recommendations do not carry to those settings, where this atlas's dialyzability and post-transplant guidance rests on other sources.Kidney Int · PMID 38519239
  • KDIGO (2021) — Executive summary of the KDIGO 2021 Guideline for the Management of Glomerular DiseasesProvides the staging/treatment framework for drug-associated glomerular lesions (e.g., bisphosphonate- and interferon-related collapsing FSGS, VEGF-inhibitor podocytopathy/proteinuria), including immunosuppression and supportive RAAS-blockade strategies.Kidney Int · PMID 34556300
  • KDIGO (2024) — Executive summary of the KDIGO 2024 Clinical Practice Guideline for the Management of ANCA-Associated VasculitisUpdates immunosuppressive induction (rituximab/cyclophosphamide), incorporates avacopan and lower-dose or glucocorticoid-sparing regimens — the management framework for drug- and checkpoint-inhibitor-associated ANCA/pauci-immune glomerulonephritis.Kidney Int · PMID 38388147
  • KDIGO (2024) — Executive summary of the KDIGO 2024 Clinical Practice Guideline for the Management of Lupus NephritisUpdates first-line lupus nephritis therapy to combination immunosuppression with the addition of belimumab or a calcineurin inhibitor (voclosporin) — informs management of immune-complex/lupus-like glomerulonephritis encountered with immunotherapy.Kidney Int · PMID 38182299
  • KDIGO (2025) — Executive summary of the KDIGO 2025 Clinical Practice Guideline for the Management of Immunoglobulin A Nephropathy (IgAN) and Immunoglobulin A Vasculitis (IgAV)Encourages liberal kidney biopsy and stricter proteinuria control (<0.5 g/d, ideally <0.3 g/d) with RAAS blockers, SGLT2 inhibitors, and targeted-release budesonide — the framework for IgA-dominant glomerular lesions, including those triggered by immune-modulating cancer therapy.Kidney Int · PMID 40975525

References

5 peer-reviewed references. Citation metadata via PubMed / NLM.

  1. 1.Dutch Pharmacogenetics Working Group (DPWG) guideline for the gene-drug interaction between UGT1A1 and irinotecan.Hulshof EC et al. · Eur J Hum Genet · 2022 · PMID 36443464
  2. 2.Irinotecan-Induced Toxicity: A Pharmacogenetic Study Beyond UGT1A1.de With M et al. · Clin Pharmacokinet · 2023 · PMID 37715926
  3. 3.Onconephrology.Kala J et al. · Crit Care Clin · 2021 · PMID 33752861
  4. 4.Onconephrology: mitigation of renal injury in chemotherapy administration.Selamet U et al. · Curr Opin Nephrol Hypertens · 2024 · PMID 38095483
  5. 5.Onconephrology: The intersections between the kidney and cancer.Rosner MH et al. · CA Cancer J Clin · 2020 · PMID 32853404
Educational monograph from NephTox (nephtox.com). Not medical advice — verify against current guidelines before any clinical decision.