Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
FOLEX 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, 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.
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.
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
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.
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.
5 mg/m2 intravenously over 2 hours daily for 5 consecutive days. Repeat 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 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 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.
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 of unchanged drug: ~80-90% within 24 hours. Biliary/fecal excretion accounts for <10%.
Renal: 50-60% as unchanged drug; biliary/fecal: minimal (<5%)
Approximately 50% bound to serum proteins, primarily albumin.
47% bound to human plasma proteins, primarily albumin.
Vd: 0.4-0.8 L/kg (total body water), indicating extensive tissue distribution; higher in pleural effusions or 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 bioavailability: dose-dependent, variable (20-80%, higher with low doses); IM: complete but slower absorption; IV: 100%.
Intravenous: 100% (only route of administration); oral: not available (no oral formulation).
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%.
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.
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.
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 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, but monitor renal function closely due to age-related decline and increased risk of toxicity.
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.
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.
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
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.
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)
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).
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.
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: 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 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 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.
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.
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.
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.
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.
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 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.
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 vs CLOLAR, 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.. 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 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 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 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 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 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. 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.