Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
FOLEX PFS 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 is a folate analog that inhibits dihydrofolate reductase (DHFR), blocking the synthesis of tetrahydrofolate and thereby interfering with DNA synthesis, repair, and cellular replication. It also exhibits immunosuppressive and anti-inflammatory effects through inhibition of purine and pyrimidine synthesis and reduction of cytokine production.
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.
Neoplastic diseases: gestational choriocarcinoma, chorioadenoma destruens, hydatidiform mole, acute lymphocytic leukemia, meningeal leukemia, breast cancer, head and neck cancer, advanced mycosis fungoides, lung cancer (especially squamous cell and small cell types), advanced non-Hodgkin's lymphomas.,Psoriasis (severe, recalcitrant, disabling, not adequately responsive to other therapy),Rheumatoid arthritis (active, severe, refractory to first-line therapy),Off-label uses: ectopic pregnancy, sarcoidosis, inflammatory bowel disease (Crohn's disease), vasculitis, systemic lupus erythematosus, dermatomyositis, juvenile idiopathic arthritis, graft-versus-host disease, multiple sclerosis, polymyositis, acute graft rejection prophylaxis
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)
Methotrexate 30-40 mg/m2 IV once weekly or 7.5-15 mg PO once weekly as single dose or divided into 3 doses over 24 hours.
52 mg/m^2 intravenously over 2 hours daily for 5 consecutive days, repeated every 28 days.
Terminal elimination half-life: 6-12 hours in patients with normal renal function. With impaired renal function, half-life is prolonged (up to 24-48 hours). Low-dose methotrexate (e.g., for rheumatoid arthritis) has half-life 3-10 hours. High-dose methotrexate has a triphasic elimination: alpha phase (0.75 hours), beta phase (3.5 hours), and terminal gamma phase (10-20 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 and intracellular metabolism to polyglutamated forms which are retained for prolonged periods. The primary metabolic pathway involves conversion to 7-hydroxymethotrexate by aldehyde oxidase. Renal excretion is the major route of elimination, with approximately 80-90% of the dose excreted unchanged in the urine within 24 hours. Enterohepatic recirculation occurs. Biliary excretion accounts for a minor fraction.
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 as unchanged drug; approximately 80-90% excreted unchanged in urine within 24 hours. Biliary/fecal excretion is minimal (<10%).
Renal: 49-60% as unchanged drug; biliary/fecal: minimal (<1%)
Approximately 50% bound to serum albumin, primarily to albumin. Binding is saturable at high doses.
47% bound to plasma proteins (primarily albumin)
Volume of distribution: 0.4-0.8 L/kg (40-80 L/70 kg). Higher doses may increase Vd due to tissue binding. Distributes into third-space fluids, including pleural effusions and ascites.
Vd: 14.6 L/kg (range 10-20 L/kg); indicates extensive extravascular distribution and tissue binding
Oral: 60-70% (dose-dependent, saturable absorption). IM: 76-100% relative to IV. IV: 100%.
IV: 100% (only IV route); oral: not approved
Cr Cl 30-60 m L/min: reduce dose by 30-50%; Cr Cl <30 m L/min: avoid use or use extreme caution with dose reduction >50%.
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).
Juvenile idiopathic arthritis: 10-15 mg/m2 IV/IM once weekly; leukemia maintenance: 15-30 mg/m2 PO/IM once weekly.
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 lower end of dosing range (e.g., 7.5-10 mg once weekly) due to reduced renal and hepatic function; monitor for myelosuppression and mucositis.
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.
WARNING: METHOTREXATE SHOULD BE USED ONLY BY PHYSICIANS EXPERIENCED IN ANTIMETABOLITE THERAPY. DEATHS HAVE BEEN REPORTED WITH THE USE OF METHOTREXATE IN THE TREATMENT OF MALIGNANCY, PSORIASIS, AND RHEUMATOID ARTHRITIS. PATIENTS SHOULD BE CLOSELY MONITORED FOR BONE MARROW SUPPRESSION, HEPATOTOXICITY, PULMONARY TOXICITY, AND RENAL TOXICITY. METHOTREXATE IS CONTRAINDICATED IN PREGNANCY AND LACTATION. DOSING FOR NON-NEOPLASTIC DISEASES (PSORIASIS AND RHEUMATOID ARTHRITIS) IS ONCE WEEKLY; DAILY DOSING HAS LED TO FATAL TOXICITY. ACCIDENTAL OVERDOSAGE HAS RESULTED IN FATALITIES.
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.
Bone marrow suppression: leukopenia, thrombocytopenia, anemia, pancytopenia,Hepatotoxicity: acute hepatitis, hepatic fibrosis, cirrhosis (especially with chronic use),Pulmonary toxicity: pneumonitis, interstitial alveolitis, pulmonary fibrosis,Renal toxicity: nephropathy, renal failure (due to precipitation of methotrexate and its metabolites in the renal tubules),Gastrointestinal toxicity: ulcerative stomatitis, diarrhea, hemorrhagic enteritis,Infections: increased risk of opportunistic infections (e.g., Pneumocystis jirovecii pneumonia),Dermatologic reactions: photosensitivity, Stevens-Johnson syndrome,Neurologic effects: encephalopathy, seizures, headache,Monitoring: baseline and periodic complete blood counts, liver function tests, renal function tests, chest X-ray,Methotrexate elimination is impaired in patients with renal impairment, ascites, or pleural effusions, leading to increased toxicity,Concurrent use of NSAIDs may 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.
Pregnancy and lactation (FDA Pregnancy Category X),Severe renal impairment (e GFR < 30 m L/min/1.73 m²),Severe hepatic impairment (cirrhosis, active hepatitis),Alcoholism or alcoholic liver disease,Pre-existing blood dyscrasias (e.g., bone marrow hypoplasia, severe anemia, leukopenia, thrombocytopenia),Active immunodeficiency syndromes (e.g., AIDS),Hypersensitivity to methotrexate or any component of the formulation,Concurrent treatment with live vaccines,Breastfeeding
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).
Foods high in folate (e.g., dark leafy greens, beans, liver) may theoretically reduce methotrexate efficacy; however, patients are often given folic acid supplements to mitigate toxicity. Caffeine may interfere with methotrexate clearance; avoid excessive caffeine intake (e.g., >4 cups coffee/day). Grapefruit and grapefruit juice may increase methotrexate levels via CYP inhibition; avoid concurrent consumption. Alcohol consumption during methotrexate therapy significantly increases risk of hepatocellular injury and is contraindicated. Avoid folic acid-fortified foods (e.g., enriched cereals, breads) in large amounts unless supplementing under medical direction.
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: severe teratogenic effects including neural tube defects, craniofacial anomalies, and limb defects. Second trimester: increased risk of fetal growth restriction, oligohydramnios, and fetal loss. Third trimester: neonatal myelosuppression, immunosuppression, and acute renal failure.
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 in breastfeeding. Methotrexate is excreted in human milk and can accumulate in neonatal tissues. M/P ratio not established but reported to be 0.08:1 in limited data.
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.
Not applicable; contraindicated in pregnancy. If inadvertent exposure occurs, immediate discontinuation is advised. Folinic acid rescue may be considered in first trimester exposure.
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.
Methotrexate (FOLEX PFS) is a folate analog antimetabolite; always confirm dose and route as intrathecal use has high risk of neurotoxicity. Leucovorin rescue is mandatory after high-dose methotrexate (typically >500 mg/m²) to prevent severe myelosuppression and mucositis. Monitor renal function closely as methotrexate is primarily renally excreted; accumulation can cause acute kidney injury. Hydration and urine alkalinization (target urine p H >7) enhance excretion and reduce nephrotoxicity. Avoid concurrent use of NSAIDs and weak acids (e.g., aspirin, penicillin) as they decrease renal clearance. Intrathecal administration carries risk of chemical arachnoiditis, seizures, and leukoencephalopathy; assess for neurotoxicity symptoms after dosing. Methotrexate can cause pneumonitis; rule out infection if new respiratory symptoms develop.
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 methotrexate exactly as prescribed; do not change dose or frequency without consulting your doctor.,Avoid alcohol completely during treatment to reduce risk of hepatotoxicity.,Drink plenty of fluids (aim for 2-3 liters daily) to prevent kidney damage.,Notify your healthcare provider immediately if you develop mouth sores, fever, chills, sore throat, easy bruising/bleeding, shortness of breath, or yellowing of skin/eyes.,Women of childbearing potential must use effective contraception during treatment and for at least 3 months after last dose; methotrexate is teratogenic.,Do not take any over-the-counter pain relievers (especially NSAIDs like ibuprofen, naproxen) without clearance, as they increase toxicity risk.,Folic acid supplementation may be prescribed to reduce side effects; take it exactly as directed.,Avoid live vaccines while on treatment and for 3 months after discontinuation.,Limit sun exposure and use sunscreen as methotrexate may increase photosensitivity.
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 PFS vs CLOFARABINE, answered by our medical review team.
FOLEX PFS is a Antineoplastic Agent that works by Methotrexate is a folate analog that inhibits dihydrofolate reductase (DHFR), blocking the synthesis of tetrahydrofolate and thereby interfering with DNA synthesis, repair, and cellular replication. It also exhibits immunosuppressive and anti-inflammatory effects through inhibition of purine and pyrimidine synthesis and reduction of cytokine production.. 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 PFS 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 PFS is: Methotrexate 30-40 mg/m2 IV once weekly or 7.5-15 mg PO once weekly as single dose or divided into 3 doses over 24 hours.. 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 PFS 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 PFS is classified as Category C. FDA Pregnancy Category X. First trimester: severe teratogenic effects including neural tube defects, craniofacial anomalies, and limb defects. Second trimester: increased risk of f. 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.