Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
FOLEX vs CLOFARABINE
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Methotrexate, the active ingredient in FOLEX, is a folate analog that inhibits dihydrofolate reductase (DHFR), blocking the conversion of dihydrofolate to tetrahydrofolate, thereby interfering with thymidylate and purine synthesis, leading to inhibition of DNA replication and cell proliferation.
Clofarabine is a purine nucleoside antimetabolite that inhibits DNA synthesis by reducing intracellular deoxynucleotide triphosphate pools via inhibition of ribonucleotide reductase, and by terminating DNA chain elongation through incorporation into DNA, leading to apoptosis.
FDA-approved: Treatment of neoplastic diseases (e.g., acute lymphoblastic leukemia, breast cancer, head and neck cancer, non-Hodgkin lymphoma, osteosarcoma),FDA-approved: Treatment of severe psoriasis (adult, recalcitrant, disabling),FDA-approved: Treatment of active rheumatoid arthritis (adult, severe, active) and polyarticular juvenile idiopathic arthritis,Off-label: Management of ectopic pregnancy,Off-label: Treatment of Crohn's disease,Off-label: Management of uveitis
Treatment of relapsed or refractory acute lymphoblastic leukemia (ALL) in pediatric patients aged 1 to 21 years,Off-label: Treatment of acute myeloid leukemia (AML), myelodysplastic syndromes (MDS)
30 mg/m2 intravenously once weekly for 2 weeks followed by a 1-week rest period, or 5-10 mg/m2 intramuscularly or intravenously every 3-4 weeks. For rheumatoid arthritis, 7.5-15 mg orally once weekly.
52 mg/m^2 intravenously over 2 hours daily for 5 consecutive days, repeated every 28 days.
Terminal half-life: 3-10 hours (mean ~5 hours) for low-dose regimens; higher doses or renal impairment may prolong half-life up to 24 hours.
Terminal elimination half-life: 5.2 hours (range 4-6 hours) in adult patients; clinically, this supports a 5-day continuous infusion schedule
Methotrexate undergoes hepatic metabolism to polyglutamate metabolites which are retained in cells. It is partially metabolized by aldehyde oxidase and xanthine oxidase. Excretion is primarily renal via glomerular filtration and active tubular secretion.
Hepatic; primarily metabolized by deamination via cytidine deaminase to 6-ketoclofarabine, a major metabolite. Also undergoes phosphorylation intracellularly. CYP450 involvement is minimal.
Primarily renal excretion of unchanged drug: ~80-90% within 24 hours. Biliary/fecal excretion accounts for <10%.
Renal: 49-60% as unchanged drug; biliary/fecal: minimal (<1%)
Approximately 50% bound to serum proteins, primarily albumin.
47% bound to plasma proteins (primarily albumin)
Vd: 0.4-0.8 L/kg (total body water), indicating extensive tissue distribution; higher in pleural effusions or ascites.
Vd: 14.6 L/kg (range 10-20 L/kg); indicates extensive extravascular distribution and tissue binding
Oral bioavailability: dose-dependent, variable (20-80%, higher with low doses); IM: complete but slower absorption; IV: 100%.
IV: 100% (only IV route); oral: not approved
GFR >50 m L/min: no adjustment; GFR 10-50 m L/min: reduce dose by 50%; GFR <10 m L/min: avoid use or reduce dose by 75%.
Clcr ≥ 60 m L/min: no adjustment; Clcr 30-59 m L/min: reduce dose to 39 mg/m^2; Clcr < 30 m L/min: not recommended (no data).
Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use.
Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 25% (monitor toxicity); Child-Pugh C: not recommended (no data).
For acute lymphoblastic leukemia: 12.5 mg/m2 orally once weekly; for juvenile idiopathic arthritis: 10-15 mg/m2 orally or subcutaneously once weekly. Maximum single dose: 20 mg.
52 mg/m^2 intravenously over 2 hours daily for 5 days every 28 days (same as adult dosing per body surface area; safety and efficacy established in pediatric patients 1 year and older).
Start at lowest end of dosing range (e.g., 5-7.5 mg orally weekly for rheumatoid arthritis) due to increased risk of toxicity from reduced renal function and folate stores.
No specific dose adjustment based solely on age; monitor renal function closely due to increased risk of nephrotoxicity; use same dosing as adults with renal adjustment as per GFR.
FOLEX (methotrexate) may cause severe toxicity including death, especially with high doses. Severe reactions include myelosuppression, hepatotoxicity, pulmonary fibrosis, renal failure, and gastrointestinal ulceration. Must be used only by physicians experienced in antimetabolite therapy. Patients should be closely monitored for bone marrow, liver, and renal toxicity.
Clofarabine causes severe bone marrow suppression, including neutropenia, anemia, thrombocytopenia, and increased risk of infection. Hemorrhage and severe infections have been reported. Monitor blood counts regularly.
Hepatotoxicity: Risk of acute and chronic liver injury, fibrosis, and cirrhosis, especially with prolonged use or pre-existing liver disease,Myelosuppression: Risk of severe pancytopenia, especially in renal impairment or with concurrent NSAIDs,Pulmonary toxicity: Acute or chronic interstitial pneumonitis, fibrosis,Renal toxicity: Acute renal failure due to precipitation of methotrexate in renal tubules, especially with high doses,Gastrointestinal toxicity: Ulceration, perforation, hemorrhage,Dermatologic reactions: Stevens-Johnson syndrome, toxic epidermal necrolysis,Concurrent NSAIDs increase methotrexate toxicity
1) Myelosuppression: monitor CBCs; dose adjustment may be needed. 2) Infections: increased susceptibility. 3) Hemorrhagic cystitis: may occur; manage with hydration and monitoring. 4) Hepatic toxicity: monitor liver function tests; dose reduction in hepatic impairment. 5) Renal toxicity: monitor renal function; dose adjustment for creatinine clearance <60 m L/min. 6) Tumor lysis syndrome: hydrate and use prophylactic allopurinol. 7) Systemic inflammatory response syndrome (SIRS): monitor for signs; discontinue if occurs.
Hypersensitivity to methotrexate or any component,Breastfeeding,Severe renal impairment (creatinine clearance <10 m L/min),Severe hepatic impairment (e.g., cirrhosis, active hepatitis),Pre-existing severe bone marrow depression (e.g., pancytopenia),Pregnancy (teratogenic and embryotoxic)
Hypersensitivity to clofarabine or any component of the formulation; severe hepatic impairment (Child-Pugh class C); severe renal impairment (creatinine clearance <30 m L/min).
Avoid alcohol completely; may increase hepatotoxicity. No specific food restrictions, but maintain adequate hydration. Avoid folic acid-rich foods (e.g., fortified cereals, legumes) if combining with leucovorin rescue in high-dose therapy due to potential interference. Take folic acid supplements at a different time than methotrexate if prescribed.
Grapefruit and grapefruit juice may affect liver enzymes and should be avoided. No specific food restrictions, but avoid alcohol due to potential hepatotoxicity. Maintain adequate hydration; no other known food interactions.
FDA Pregnancy Category X. First trimester: High risk of miscarriage, neural tube defects, craniofacial anomalies, and limb defects. Second and third trimesters: Fetal growth restriction, skeletal abnormalities, functional deficits. Avoid use during pregnancy.
Clofarabine is embryotoxic and teratogenic in animal studies. In humans, it is classified as Pregnancy Category D. First trimester exposure is associated with major congenital malformations including neural tube defects, skeletal anomalies, and cardiovascular defects. Second and third trimester exposure may cause fetal myelosuppression, intrauterine growth restriction, and premature delivery.
Contraindicated during breastfeeding. Methotrexate (active component) is excreted in breast milk with an M/P ratio of approximately 0.08; risk of infant accumulation due to long half-life. Do not breastfeed during therapy or for at least 1 week after last dose.
It is unknown whether clofarabine is excreted in human breast milk. Due to the potential for serious adverse reactions in nursing infants, breastfeeding is contraindicated during therapy and for at least 1 week after the last dose. M/P ratio is not available.
Pregnancy is a contraindication; no dose adjustments are recommended. If used inadvertently, immediate discontinuation and high-dose folic acid rescue. Pharmacokinetic changes in pregnancy (increased Vd and clearance) may require dose reduction if used for non-pregnant patients, but absolute contraindication overrides.
No specific pharmacokinetic studies have been conducted in pregnant women. Dose adjustments based on pregnancy-induced physiologic changes (increased plasma volume, renal clearance) are not established. Use with caution; the lowest effective dose based on tolerability and clinical response is recommended. Close monitoring for toxicity is essential.
Folex (methotrexate) is a folate analog antimetabolite used in oncology and autoimmune diseases. Administer leucovorin rescue 24 hours after high-dose methotrexate to prevent severe toxicity. Monitor renal function and methotrexate levels closely. Avoid NSAIDs as they reduce renal clearance and increase toxicity. Hepatotoxicity and pulmonary fibrosis are serious adverse effects. Intrathecal administration requires preservative-free formulation.
Clofarabine is a purine nucleoside antimetabolite used primarily in pediatric relapsed or refractory acute lymphoblastic leukemia (ALL). It is associated with significant myelosuppression; monitor absolute neutrophil count and platelets closely. Capillary leak syndrome and systemic inflammatory response syndrome (SIRS) are rare but serious adverse effects; consider prophylactic corticosteroids. Hepatic veno-occlusive disease (VOD) has been reported, especially in patients with prior stem cell transplant. Administer with adequate hydration and monitor for tumor lysis syndrome.
Take folic acid supplements as prescribed to reduce side effects unless on high-dose therapy with leucovorin rescue.,Avoid alcohol completely during treatment due to increased risk of liver damage.,Report any signs of infection, unusual bleeding, or shortness of breath immediately.,Drink plenty of fluids to help flush the drug from your kidneys unless otherwise instructed.,Do not take any over-the-counter medications, especially NSAIDs (like ibuprofen), without consulting your doctor.,Use effective contraception during and for at least 3 months after treatment for both men and women.,Follow your dosing schedule exactly; missed doses can reduce effectiveness or increase toxicity.
Clofarabine is a chemotherapy drug that may lower your blood cell counts, increasing risk of infection, bleeding, and fatigue.,Report any signs of infection (fever, chills, sore throat), unusual bleeding or bruising, or shortness of breath immediately.,Drink plenty of fluids (8-10 glasses per day) to prevent kidney problems and tumor lysis syndrome.,Avoid live vaccines and close contact with people who have recently received oral polio vaccine.,Use effective contraception during treatment and for at least 6 months after the last dose.,Do not breastfeed while taking clofarabine.,You may experience nausea, vomiting, or diarrhea; your doctor can prescribe medications to manage these symptoms.
No interactions on record
"Clofarabine, a purine nucleoside antimetabolite used in hematologic malignancies, may reduce the metabolism of Eltrombopag, a thrombopoietin receptor agonist, via inhibition of UDP-glucuronosyltransferase (UGT) enzymes, particularly UGT1A1 and UGT1A3. This leads to increased systemic exposure of Eltrombopag, potentially elevating the risk of hepatotoxicity (e.g., elevated liver enzymes) and other adverse effects such as thrombosis. Clinical outcomes may include exacerbated liver injury, which is particularly concerning in patients with pre-existing hepatic impairment or those receiving other hepatotoxic agents."
"Concurrent use of clofarabine and mecamylamine may synergistically increase the risk of severe hypotension and syncope. Clofarabine is a purine nucleoside analog that can cause capillary leak syndrome and hypotension, while mecamylamine is a ganglionic blocker that inhibits sympathetic outflow, leading to orthostatic hypotension. The combined hypotensive effects may result in profound blood pressure reduction, dizziness, and potential falls, particularly in patients with impaired cardiovascular function."
"The combination of clofarabine and nifedipine may increase the risk of cardiotoxicity, particularly QT interval prolongation and left ventricular dysfunction. Clofarabine has been associated with pericardial effusion and cardiac tamponade, while nifedipine, a calcium channel blocker, can cause hypotension and reflex tachycardia, potentially compounding hemodynamic stress in patients with compromised cardiac function. Clinical outcomes may include arrhythmias, heart failure exacerbation, or sudden cardiac death, especially in patients with preexisting cardiovascular risk factors."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about FOLEX vs CLOFARABINE, answered by our medical review team.
FOLEX is a Antineoplastic Agent that works by Methotrexate, the active ingredient in FOLEX, is a folate analog that inhibits dihydrofolate reductase (DHFR), blocking the conversion of dihydrofolate to tetrahydrofolate, thereby interfering with thymidylate and purine synthesis, leading to inhibition of DNA replication and cell proliferation.. CLOFARABINE is a Antineoplastic Agent that works by Clofarabine is a purine nucleoside antimetabolite that inhibits DNA synthesis by reducing intracellular deoxynucleotide triphosphate pools via inhibition of ribonucleotide reductase, and by terminating DNA chain elongation through incorporation into DNA, leading to apoptosis.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between FOLEX and CLOFARABINE depend on the specific clinical indication. These are both Antineoplastic Agent agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of FOLEX is: 30 mg/m2 intravenously once weekly for 2 weeks followed by a 1-week rest period, or 5-10 mg/m2 intramuscularly or intravenously every 3-4 weeks. For rheumatoid arthritis, 7.5-15 mg orally once weekly.. The standard adult dose of CLOFARABINE is: 52 mg/m^2 intravenously over 2 hours daily for 5 consecutive days, repeated every 28 days.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between FOLEX and CLOFARABINE in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. FOLEX is classified as Category C. FDA Pregnancy Category X. First trimester: High risk of miscarriage, neural tube defects, craniofacial anomalies, and limb defects. Second and third trimesters: Fetal growth restri. CLOFARABINE is classified as Category C. Clofarabine is embryotoxic and teratogenic in animal studies. In humans, it is classified as Pregnancy Category D. First trimester exposure is associated with major congenital malf. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.