Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
FOLEX vs CLADRIBINE
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.
Cladribine is a purine nucleoside analog that is phosphorylated intracellularly to its active triphosphate form, which inhibits DNA synthesis and repair, leading to cell death, particularly in lymphocytes. It also depletes adenosine deaminase (ADA) and accumulates in cells with high deoxycytidine kinase activity.
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-approved: Treatment of hairy cell leukemia.,Off-label: Chronic lymphocytic leukemia (CLL), multiple sclerosis (relapsing forms), Waldenström macroglobulinemia, cutaneous T-cell lymphoma, and as part of conditioning regimens for hematopoietic stem cell transplantation.
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.
0.09 mg/kg/day IV over 2 hours for 7 consecutive days; or 0.14 mg/kg/day IV over 2 hours for 5 consecutive days (total dose 0.7 mg/kg per course).
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 is approximately 5.4 hours (range 4.6–6.7 hours) after intravenous administration; prolonged in renal impairment.
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.
Cladribine is primarily metabolized intracellularly by deoxycytidine kinase to its active triphosphate. It is also phosphorylated by deoxyguanosine kinase in mitochondria. Catabolism involves deamination by adenosine deaminase (ADA) to 2-chloroadenine, which is further metabolized.
Primarily renal excretion of unchanged drug: ~80-90% within 24 hours. Biliary/fecal excretion accounts for <10%.
Renal (approximately 50% as unchanged drug); fecal elimination is minimal (<5%).
Approximately 50% bound to serum proteins, primarily albumin.
Approximately 20–30% bound to plasma proteins.
Vd: 0.4-0.8 L/kg (total body water), indicating extensive tissue distribution; higher in pleural effusions or ascites.
Approximately 4.5 L/kg (range 2.3–9.6 L/kg), indicating extensive tissue distribution.
Oral bioavailability: dose-dependent, variable (20-80%, higher with low doses); IM: complete but slower absorption; IV: 100%.
Oral: approximately 37–55% (first-pass metabolism); subcutaneous: approximately 100%.
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%.
GFR <50 m L/min: reduce dose by 50%; GFR <10 m L/min: avoid use.
Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use.
Child-Pugh Class B: reduce dose by 50%; Child-Pugh Class C: contraindicated.
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.
0.09 mg/kg/day IV over 2 hours for 7 consecutive days; or 0.14 mg/kg/day IV over 2 hours for 5 consecutive days (total dose 0.7 mg/kg per course). No specific pediatric dose adjustments beyond weight-based dosing.
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 recommended; monitor renal function and adjust accordingly.
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: Neurotoxicity and Hematologic Toxicity. Cladribine can cause severe bone marrow suppression (neutropenia, anemia, thrombocytopenia) and neurotoxicity (including paralysis, coma, and death). Dose-dependent and more frequent in high doses.
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
Myelosuppression: Monitor blood counts regularly; dose adjustment or discontinuation may be needed.,Neurotoxicity: Risk increased with high doses and in patients with renal impairment.,Nephrotoxicity: Use with caution in renal impairment; reduce dose if Cr Cl < 60 m L/min.,Hepatotoxicity: Monitor liver function tests.,Secondary malignancies: Increased risk of myelodysplasia and acute myeloid leukemia.,Infections: Increased susceptibility due to lymphopenia; consider prophylaxis.
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 cladribine or any component of the formulation.,Pre-existing severe bone marrow suppression (e.g., neutropenia, thrombocytopenia) unless due to underlying disease.,Pregnancy: Can cause fetal harm.,Lactation: Discontinue nursing or drug.
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 significant food interactions. Avoid grapefruit juice due to potential CYP3A4 interaction (though minimal). Maintain adequate hydration to prevent tumor lysis syndrome in hematologic malignancies.
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.
FDA Pregnancy Category D. First trimester: Avoid due to known teratogenicity in animal studies (skeletal and visceral malformations) and potential for MDS and AML. Second and third trimesters: Risk of fetal myelosuppression, intrauterine growth restriction, and preterm labor. Cladribine crosses the placenta and may cause fetal hematopoietic suppression.
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.
Contraindicated during breastfeeding. Cladribine is excreted into human milk; M/P ratio not determined. Potential for severe adverse effects in nursing infants, including myelosuppression and immunosuppression. Discontinue breastfeeding during therapy and for at least 7 days after last dose.
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 established dose adjustments in pregnancy. Use is contraindicated. If unavoidable, lowest effective dose and close monitoring for maternal and fetal toxicity. Pharmacokinetic changes in pregnancy (increased volume of distribution, renal clearance) may reduce exposure; however, risks outweigh benefits.
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.
Cladribine is a purine nucleoside analog that causes lymphocyte depletion, effective in hairy cell leukemia and multiple sclerosis. Monitor for severe lymphopenia, opportunistic infections (e.g., herpes zoster, tuberculosis), and delayed myelosuppression. Do not administer live vaccines during or after treatment. Due to high bioavailability after subcutaneous administration, adjust dose for renal impairment. Hypersensitivity reactions may occur; premedicate with antihistamines if needed.
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.
Cladribine can significantly lower your white blood cell count, increasing infection risk. Report fever, chills, or sore throat immediately.,Avoid live vaccines (e.g., MMR, shingles) during and for at least 6 months after treatment.,You may experience fatigue, nausea, headache, or skin reactions at injection site. These are common but report severe symptoms.,Use effective contraception during treatment and for at least 6 months after the last dose. Cladribine may harm a fetus.,You will need regular blood tests to monitor your blood cell counts, liver, and kidney function.
No interactions on record
"The combination of cabazitaxel and cladribine may potentiate myelosuppression due to overlapping bone marrow toxicity profiles. Cabazitaxel, a taxane antineoplastic, inhibits microtubule disassembly, while cladribine, a purine analog, incorporates into DNA and induces apoptosis in dividing and resting lymphocytes. Concurrent use increases the risk of severe neutropenia, thrombocytopenia, and anemia, potentially leading to febrile neutropenia or bleeding complications."
"Cladribine, a purine nucleoside analog with potent immunosuppressive properties, may reduce the pharmacodynamic effects of cardiac glycosides such as acetyldigitoxin. This interaction is hypothesized to occur through cladribine-induced modulation of myocardial cellular signaling pathways that decrease sensitivity to digitalis compounds, potentially leading to reduced inotropic efficacy. Clinically, this could manifest as diminished control of heart rate in patients with atrial fibrillation or worsening heart failure symptoms, particularly in those relying on acetyldigitoxin for rate control or inotropic support."
"The risk or severity of adverse effects can be increased when Pimecrolimus is combined with Cladribine."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about FOLEX vs CLADRIBINE, 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.. CLADRIBINE is a Antineoplastic Agent that works by Cladribine is a purine nucleoside analog that is phosphorylated intracellularly to its active triphosphate form, which inhibits DNA synthesis and repair, leading to cell death, particularly in lymphocytes. It also depletes adenosine deaminase (ADA) and accumulates in cells with high deoxycytidine kinase activity.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between FOLEX and CLADRIBINE 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 CLADRIBINE is: 0.09 mg/kg/day IV over 2 hours for 7 consecutive days; or 0.14 mg/kg/day IV over 2 hours for 5 consecutive days (total dose 0.7 mg/kg per course).. 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 CLADRIBINE 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. CLADRIBINE is classified as Category C. FDA Pregnancy Category D. First trimester: Avoid due to known teratogenicity in animal studies (skeletal and visceral malformations) and potential for MDS and AML. Second and third. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.