The clinical companion
Beyond which drug hurts the kidney — how to act on it. An electrolyte mini-atlas, dosing in dialysis and CKD, and the pediatric and transplant angles, each grounded in the literature.
Electrolyte mini-atlas
Hypomagnesemia
- Mechanism
- Anti-EGFR monoclonal antibodies block EGFR signaling in the distal convoluted tubule, downregulating the TRPM6 magnesium channel and causing renal Mg2+ wasting. Cisplatin injures the proximal and distal tubule, impairing Mg2+ (and K+/Ca2+) reabsorption; the defect can persist for months to years after therapy.
- Presentation
- Often asymptomatic and detected on labs; when severe, neuromuscular irritability, tetany, tremor, seizures, and refractory hypokalemia/hypocalcemia. Magnesium wasting with anti-EGFR antibodies is dose- and duration-dependent and very common with prolonged therapy.
- Management
- Monitor Mg2+ before and during therapy. Oral Mg salts are limited by diarrhea; symptomatic or severe deficits usually need IV magnesium sulfate, sometimes as repeated/scheduled infusions. Correct coexisting hypokalemia/hypocalcemia (often refractory until Mg2+ is repleted). Hold or dose-reduce the culprit for severe cases.
Hyponatremia (SIADH)
- Mechanism
- Several agents cause a syndrome of inappropriate antidiuretic hormone secretion (SIADH). High-dose cyclophosphamide potentiates renal water reabsorption (and is given with large hypotonic fluid loads), and vinca alkaloids are classically associated with SIADH. EGFR-TKIs have rare reported SIADH. Platinum agents can also produce hypotonic hyponatremia when nephrotoxicity-prevention hydration uses hypotonic fluid.
- Presentation
- Euvolemic hyponatremia with low serum osmolality, inappropriately concentrated urine, and elevated urine sodium. Symptoms track severity/acuity: nausea, headache, confusion, and — when severe/acute — seizures and obtundation.
- Management
- Confirm SIADH (euvolemia, urine osm > serum osm, U[Na] typically > 30 mmol/L). Fluid restriction is first-line; avoid hypotonic fluids around cyclophosphamide. Hypertonic (3%) saline for severe/symptomatic cases with careful correction limits to avoid osmotic demyelination. For EGFR-TKI SIADH, dose reduction has allowed continued therapy in case reports.
Hyperphosphatemia
- Mechanism
- FGFR inhibitors block FGF23–FGFR/Klotho signaling in the proximal tubule, increasing renal phosphate reabsorption and raising serum phosphate. Hyperphosphatemia is an on-target, class effect and is used as a pharmacodynamic marker of adequate FGFR target engagement.
- Presentation
- Usually asymptomatic lab elevation; sustained/marked elevation risks soft-tissue and vascular calcification and cutaneous calcinosis. With erdafitinib it is among the most frequent adverse events.
- Management
- Monitor serum phosphate on a defined schedule. Institute a low-phosphate diet and add phosphate binders when phosphate exceeds the protocol threshold; restrict vitamin D supplementation. Dose-reduce, interrupt, or discontinue the FGFR inhibitor per phosphate level. (Note: the inhibitor-defined target phosphate range is part of dosing algorithms, distinct from CKD-MBD targets.)
Hypophosphatemia (Fanconi / FGF23)
- Mechanism
- Ifosfamide (via the metabolite chloroacetaldehyde) injures the proximal tubule and can cause acquired Fanconi syndrome — phosphaturia, glucosuria, aminoaciduria, bicarbonate wasting, and hypouricemia. Separately, FGF23-driven phosphate wasting (e.g., tumor-induced osteomalacia from FGF23-secreting mesenchymal tumors) causes renal phosphate loss with inappropriately low/normal 1,25-OH vitamin D.
- Presentation
- Proximal tubulopathy: hypophosphatemia, renal tubular acidosis, glucosuria with normoglycemia, low-molecular-weight proteinuria. Chronic phosphate depletion causes muscle weakness, bone pain, osteomalacia, and — in growing children — rickets and growth failure.
- Management
- Oral phosphate and calcitriol replacement; correct acidosis with bicarbonate/citrate. Monitor phosphate, bicarbonate, glucose, and growth (children). For FGF23-mediated tumor-induced osteomalacia, definitive treatment is tumor resection; burosumab (anti-FGF23) is an option when resection is not feasible.
Hypokalemia
- Mechanism
- Abiraterone (CYP17 inhibition) causes a compensatory rise in ACTH and upstream mineralocorticoid (e.g., corticosterone, deoxycorticosterone) excess, driving renal potassium wasting, hypertension, and fluid retention. Cisplatin-induced tubular injury causes renal K+ (and Mg2+) wasting; hypokalemia is frequently refractory until magnesium is corrected.
- Presentation
- Weakness, cramps, ileus, arrhythmia; with abiraterone, accompanying hypertension and edema. The abiraterone mineralocorticoid syndrome is dose-related.
- Management
- For abiraterone, co-administer prednisone/prednisolone to suppress ACTH-driven mineralocorticoid excess; add a mineralocorticoid-receptor antagonist (e.g., eplerenone — avoid spironolactone, which can stimulate the androgen receptor) for refractory cases, plus K+ repletion. For platinum-associated loss, replete K+ and correct coexisting hypomagnesemia.
Hypocalcemia
- Mechanism
- Potent anti-resorptive therapy (RANKL inhibition by denosumab; bisphosphonates) abruptly halts osteoclastic bone resorption, lowering calcium efflux from bone. Risk is amplified by vitamin D deficiency and by impaired kidney function (reduced renal 1,25-OH vitamin D and phosphate handling).
- Presentation
- Perioral/distal paresthesias, carpopedal spasm, Chvostek/Trousseau signs, QT prolongation, and — when severe — tetany or seizures. Often within days to weeks of dosing, particularly the higher oncology (bone-metastasis/myeloma) dosing.
- Management
- Correct vitamin D and replete calcium BEFORE and during therapy; check calcium (corrected/ionized), magnesium, and 25-OH vitamin D. Use special caution in CKD/dialysis (higher hypocalcemia risk). Treat symptomatic/severe hypocalcemia with IV calcium and ongoing oral calcium plus active vitamin D.
Tumor lysis electrolytes (hyperK / hyperphos / hyperuricemia)
- Mechanism
- Rapid lysis of tumor cells releases intracellular contents: potassium, phosphate, and nucleic acids (catabolized to uric acid). Hyperphosphatemia drives calcium-phosphate precipitation (causing secondary hypocalcemia) and, with uric acid, intratubular crystal deposition and acute kidney injury.
- Presentation
- Cairo–Bishop laboratory/clinical TLS: hyperkalemia, hyperphosphatemia, hyperuricemia, and hypocalcemia, with AKI, arrhythmia, seizures, and tetany. Typically within 12–72 h of starting therapy for bulky, chemosensitive tumors; highest risk in Burkitt lymphoma and acute leukemias.
- Management
- Risk-stratify and prevent: aggressive IV hydration, rasburicase for high-risk/established hyperuricemia (allopurinol for lower risk), cardiac monitoring, and treatment of hyperkalemia. Manage hyperphosphatemia with binders; renal replacement therapy for refractory electrolyte derangement, oliguric AKI, or volume overload. Avoid alkalinization when using rasburicase.
Dosing in dialysis & CKD
Dose by target AUC using the Calvert formula (dose = AUC x (GFR + 25)); accurate GFR is essential because carboplatin is almost entirely renally cleared. Free (non-protein-bound) carboplatin is dialyzable. In ESKD, individualized reduced AUC targets with chemotherapy timed relative to a hemodialysis session are used; coordinate dosing and HD timing with pharmacy.
Directly nephrotoxic; requires vigorous saline hydration ± mannitol and Mg/K repletion. Reduce dose or avoid with reduced CrCl (commonly substitute carboplatin). Only unbound platinum is removed by dialysis and it binds plasma proteins rapidly, so HD does not reliably rescue toxicity once bound.
Renally eliminated; AKI causes dangerous drug accumulation. Prevent with hydration, urinary alkalinization, and leucovorin rescue. For delayed clearance/AKI, glucarpidase rapidly cleaves plasma methotrexate (>87% reduction) and is preferred; high-flux/high-efficiency hemodialysis removes methotrexate but levels rebound, so it is adjunctive, not first-line.
Predominantly renal elimination; reduce dose with impaired CrCl and use cautiously (limited data) in moderate-to-severe impairment. Avoid in severe renal failure where data are sparse; dialyzability is not well characterized.
Substantial renal clearance; reduce dose for moderate renal impairment (commonly halved at low CrCl, e.g., CrCl 20–39 mL/min) per label. Limited dialysis data; HD timing data are sparse, so treat as not reliably removed.
About 40% renally excreted; reduce dose with reduced CrCl (e.g., ~25% reduction at CrCl 15–50 mL/min). Highly protein-bound, so it is not appreciably removed by hemodialysis — no rescue benefit and no need to dose around HD for removal.
Predominantly renally excreted; dose-reduce and extend the interval as CrCl falls. On hemodialysis it is removed, so the dose is given AFTER the HD session on dialysis days. Adjust by CrCl bands per label.
5-FU metabolites accumulate in renal impairment, increasing toxicity. Reduce dose at moderate impairment (CrCl 30–50 mL/min) and CONTRAINDICATED at CrCl < 30 mL/min. Avoid in dialysis-dependent patients given accumulation risk and limited removal data.
Large IgG monoclonal antibody cleared by reticuloendothelial/target-mediated routes, not the kidney. No renal dose adjustment and it is NOT removed by dialysis (too large to cross the membrane), so no dose timing around HD is required. Watch for TLS when treating bulky CD20+ disease.
IgG antibodies are not renally cleared and are NOT removed by hemodialysis; no dose adjustment for CrCl or dialysis. Case series report efficacy and acceptable safety in ESKD/dialysis patients. Remain alert for immune-related AKI (most often acute interstitial nephritis) and, in transplant recipients, allograft rejection.
Large proteins not eliminated renally and not dialyzed; no renal dose adjustment. Main onconephrology concern is cytokine-release-syndrome physiology (hemodynamics, AKI) and TLS, not drug accumulation. Limited dedicated ESKD pharmacokinetic data — monitor clinically.
A living cell product — not a renally cleared or dialyzable drug. AKI risk derives from cytokine release syndrome, tumor lysis, and supportive-care exposures rather than the cells themselves. Lymphodepleting chemotherapy (fludarabine/cyclophosphamide) does need renal dose adjustment.
The radioligand and its activity are renally excreted; kidneys are a dose-limiting organ. In dialysis-dependent patients it has been delivered with a planned HD schedule to clear circulating activity and manage radiation safety, with HD timed after administration (case-level evidence). Requires nuclear-medicine and nephrology coordination plus radiation-protection handling of effluent.
General rule: small renally-cleared cytotoxics need CrCl-based dose reduction and some are dialyzable (carboplatin, methotrexate, lenalidomide); large proteins (rituximab, checkpoint inhibitors, bispecifics) and cell therapies (CAR-T) are NOT renally cleared and NOT dialyzed, so they generally need no renal dose change — the kidney risk is downstream (TLS, CRS, immune-related AKI).
Pediatric onconephrology
Ifosfamide nephrotoxicity, Fanconi syndrome & rickets
Ifosfamide is a leading cause of chronic tubular nephrotoxicity in children, producing proximal (and sometimes glomerular) injury and acquired Fanconi syndrome — phosphaturia, renal tubular acidosis, glucosuria, and aminoaciduria. Younger age (especially under ~3–5 years) and higher cumulative dose increase risk. Persistent phosphate wasting can cause hypophosphatemic rickets, growth impairment, and long-term CKD; survivors need ongoing monitoring of phosphate, bicarbonate, and growth.
Carboplatin pediatric GFR-based dosing (Newell formula)
Children's carboplatin dosing is individualized to renal function. The Newell pediatric formula (dose (mg) = target AUC x (GFR + a body-size term)) was derived to target a defined plasma AUC and improves dosing accuracy over body-surface-area dosing, especially in infants where GFR and body size diverge. Accurate (ideally measured) GFR is essential because carboplatin clearance is almost entirely renal.
Cisplatin ototoxicity and nephrotoxicity
Cisplatin causes dose-dependent, often irreversible sensorineural hearing loss in children (a major late effect, with developmental/educational consequences) plus tubular nephrotoxicity with Mg2+/K+ wasting. In a randomized trial, sodium thiosulfate reduced the incidence of cisplatin-induced hearing loss in children with standard-risk hepatoblastoma and other tumors (with attention to potential effects on tumor control in disseminated disease). Hydration and electrolyte repletion mitigate renal injury.
Long-term CKD in childhood-cancer survivors
Survivors of childhood cancer carry an elevated long-term risk of CKD, hypertension, proteinuria, and chronic electrolyte abnormalities driven by nephrotoxic exposures (platinums, ifosfamide, methotrexate), nephrectomy, abdominal/total-body irradiation, and stem-cell transplant. Risk-stratified, lifelong kidney surveillance (eGFR, blood pressure, urinalysis) is recommended, with nephrology referral for those with established kidney injury.
Tumor lysis syndrome in pediatric ALL and Burkitt lymphoma
TLS is most frequent and severe in pediatric high-burden, rapidly proliferating malignancies — Burkitt lymphoma/leukemia and T-cell ALL — and can occur spontaneously or after starting therapy. Management mirrors adults: risk stratification, aggressive hydration, rasburicase for high-risk hyperuricemia, cardiac monitoring, and renal replacement therapy for refractory derangements, with hyperphosphatemia and secondary hypocalcemia often the most troublesome features in children.
Transplant onconephrology
Cancer risk in kidney-transplant recipients
Solid-organ transplant recipients have roughly a two-fold overall increase in cancer incidence versus the general population, with markedly higher risk for virus-associated malignancies (non-Hodgkin lymphoma, Kaposi sarcoma, anogenital and skin cancers) as well as several non-infection-related cancers. Chronic immunosuppression and oncogenic viral infection drive the excess risk, motivating cancer screening and judicious immunosuppression minimization in kidney-transplant recipients.
Checkpoint inhibitors and allograft rejection risk
Immune checkpoint inhibitors can precipitate acute allograft rejection in kidney-transplant recipients. In a multicenter cohort, about 42% of treated recipients developed acute rejection, frequently leading to graft loss, with rejection typically occurring early (median ~24 days). mTOR-inhibitor-based and triple-agent immunosuppression were associated with lower rejection risk, and some patients still derived meaningful antitumor benefit — so ICI use requires explicit shared decision-making, baseline immunosuppression optimization, and close graft monitoring.
mTOR inhibitors: dual anticancer and immunosuppressant role
Sirolimus and everolimus are unique in being both maintenance immunosuppressants and antiproliferative anticancer agents. In transplant recipients, mTOR-inhibitor-based regimens are associated with reduced incidence of certain post-transplant malignancies (notably skin cancers) and are favored when malignancy risk is a concern, though tolerability (proteinuria, mouth ulcers, metabolic effects) and rejection risk temper their use. Their anticancer activity also underlies oncology indications (e.g., renal cell carcinoma, certain breast cancers).
Post-transplant lymphoproliferative disorder (PTLD)
PTLD is a serious complication of chronic immunosuppression, most commonly B-cell and frequently Epstein–Barr virus (EBV)-driven, especially in EBV-seronegative recipients of seropositive donors. Management starts with reduction of immunosuppression, often with rituximab for CD20+ disease and chemotherapy for aggressive/refractory cases; EBV viral-load monitoring and pre-emptive immunosuppression reduction are used in high-risk recipients.
Drug-interaction cautions with calcineurin inhibitors
Cyclosporine and tacrolimus are CYP3A4 and P-glycoprotein substrates with narrow therapeutic windows, so co-administered cancer therapies and supportive drugs that inhibit or induce CYP3A4 can cause large swings in calcineurin-inhibitor levels — risking nephrotoxicity/neurotoxicity (with inhibitors) or rejection (with inducers). Anticipate interactions with azole antifungals, certain tyrosine-kinase inhibitors, and other CYP3A4 modulators; monitor trough levels closely and adjust dosing proactively around any new oncologic regimen.
Evidence
34 verified references. Citation metadata via PubMed / NLM.