Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
FOLEX PFS vs CLOLAR
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.
Clolar (clofarabine) is a purine nucleoside antimetabolite that inhibits DNA synthesis and RNA transcription. It is phosphorylated intracellularly to its active triphosphate form, which competes with adenosine triphosphate for incorporation into DNA, leading to chain termination and inhibition of DNA polymerase and ribonucleotide reductase, resulting in 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
FDA: 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), chronic myeloid leukemia (CML) in blast crisis.
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.
5 mg/m2 intravenously over 2 hours daily for 5 consecutive days. Repeat 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 approximately 5.2 hours in patients with normal renal function; prolonged in renal impairment (up to 9.8 hours with Cr Cl <60 m L/min) and in elderly; clinical context: supports once-daily dosing adjustment for renal function.
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.
Clofarabine is partially metabolized by deamination via cytidine deaminase (CDA) to inactive 6-keto-clofarabine. Approximately 50-60% of the drug is excreted unchanged in urine.
Primarily renal excretion as unchanged drug; approximately 80-90% excreted unchanged in urine within 24 hours. Biliary/fecal excretion is minimal (<10%).
Renal: 50-60% as unchanged drug; biliary/fecal: minimal (<5%)
Approximately 50% bound to serum albumin, primarily to albumin. Binding is saturable at high doses.
47% bound to human 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.
Central Vd approximately 172 L/m² (extensive tissue distribution); in L/kg: ~4.6 L/kg (assuming 70 kg patient with BSA 1.73 m²). Clinical meaning: indicates wide distribution into total body water and tissues, exceeding total body water.
Oral: 60-70% (dose-dependent, saturable absorption). IM: 76-100% relative to IV. IV: 100%.
Intravenous: 100% (only route of administration); oral: not available (no oral formulation).
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%.
Cr Cl >= 60 m L/min: no adjustment. Cr Cl 30-59 m L/min: reduce dose by 20%. Cr Cl < 30 m L/min: contraindicated.
Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use.
No specific guidelines; use caution in severe hepatic impairment (Child-Pugh class C) and consider dose reduction based on tolerability.
Juvenile idiopathic arthritis: 10-15 mg/m2 IV/IM once weekly; leukemia maintenance: 15-30 mg/m2 PO/IM once weekly.
1-21 years: 5 mg/m2 IV over 2 hours daily for 5 days every 28 days; reduce dose by 50% in patients with renal impairment.
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, but monitor renal function closely due to age-related decline and increased risk of toxicity.
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.
WARNING: HEMATOLOGIC TOXICITY, INFECTION, AND HEPATIC TOXICITY. Clolar suppresses bone marrow function, causing severe neutropenia, thrombocytopenia, and anemia. Fatal infections have occurred. Hepatic toxicity, including hepatic failure and death, has been reported. Monitor blood counts and liver function frequently.
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
Bone marrow suppression: severe neutropenia, thrombocytopenia, and anemia require close monitoring. Infections: serious and fatal infections (bacterial, fungal, viral) may occur. Hepatic toxicity: elevation of liver enzymes, bilirubin, and hepatic veno-occlusive disease. Renal toxicity: increased creatinine, hematuria, and hemolytic uremic syndrome-like reactions. Cardiac toxicity: pericardial effusion, hypotension, and ventricular dysfunction. Tumor lysis syndrome. Hypersensitivity reactions. Use in pregnancy: embryo-fetal toxicity. Vaccination: avoid live vaccines.
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
Absolute: Hypersensitivity to clofarabine or any component of the formulation. Relative: Severe hepatic impairment (bilirubin >3 mg/d L or transaminases >5x ULN). 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.
No specific food interactions are documented. However, maintain adequate hydration to reduce risk of nephrotoxicity and tumor lysis syndrome. Avoid grapefruit and grapefruit juice as they may affect metabolism via CYP3A4 (theoretical concern, though clofarabine is primarily renally excreted).
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 contraindicated in pregnancy. Based on its mechanism of action (inhibitor of DNA synthesis) and animal studies, there is a high risk of fetal harm if administered during pregnancy. In the first trimester, there is a significant risk of embryolethality and teratogenicity (structural anomalies). In the second and third trimesters, fetal growth restriction and central nervous system damage may occur. Pregnancy must be excluded before initiation.
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.
No data available on the excretion of clofarabine into breast milk or its effects on the nursing infant. Due to potential for serious adverse reactions (e.g., myelosuppression, gastrointestinal toxicity), breastfeeding is contraindicated during therapy and for at least 3 months after the last dose. M/P ratio is unknown.
Not applicable; contraindicated in pregnancy. If inadvertent exposure occurs, immediate discontinuation is advised. Folinic acid rescue may be considered in first trimester exposure.
There are no established dose adjustments for clofarabine during pregnancy, as use is contraindicated. Physiological changes in pregnancy (e.g., increased plasma volume, altered renal clearance) may affect pharmacokinetics, but no dosing guidelines exist. If inadvertent exposure occurs, immediate discontinuation is recommended and the pregnancy should be managed by a maternal-fetal medicine specialist.
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.
Clolar (clofarabine) is a purine nucleoside analog indicated for pediatric relapsed/refractory acute lymphoblastic leukemia. Key pearls: (1) Monitor for systemic inflammatory response syndrome (SIRS) and capillary leak syndrome; premedicate with corticosteroids. (2) Requires aggressive hydration and allopurinol for tumor lysis prophylaxis. (3) Dose reductions needed for renal impairment (Cr Cl < 60 m L/min). (4) Avoid live vaccines during and after treatment.
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.
Clolar is a chemotherapy drug used to treat a type of leukemia in children that has not responded to other treatments.,You may experience side effects like fever, nausea, vomiting, diarrhea, and skin rashes. Report any signs of infection or unusual bleeding.,Drink plenty of fluids as directed to prevent kidney problems. You may receive IV fluids before and after treatment.,Avoid vaccinations without doctor approval, as live vaccines are not safe during treatment.,This drug can cause severe reactions including organ inflammation and fluid retention; seek immediate medical help if you have difficulty breathing, rapid weight gain, or swelling.
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about FOLEX PFS vs CLOLAR, 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.. CLOLAR is a Antineoplastic Agent that works by Clolar (clofarabine) is a purine nucleoside antimetabolite that inhibits DNA synthesis and RNA transcription. It is phosphorylated intracellularly to its active triphosphate form, which competes with adenosine triphosphate for incorporation into DNA, leading to chain termination and inhibition of DNA polymerase and ribonucleotide reductase, resulting in apoptosis.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between FOLEX PFS and CLOLAR 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 CLOLAR is: 5 mg/m2 intravenously over 2 hours daily for 5 consecutive days. Repeat 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 CLOLAR 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. CLOLAR is classified as Category C. Clofarabine is contraindicated in pregnancy. Based on its mechanism of action (inhibitor of DNA synthesis) and animal studies, there is a high risk of fetal harm if administered du. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.