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MEDICINE MONOGRAPH CODE: [7.12] ID: TIP-MED-000114 ⚠️ HIGH-ALERT / SPECIALIST SUPERVISION

Methotrexate (Low-Dose Weekly Immunomodulator / DMARD Regimen)

Active Ingredient / Scientific Identity: Methotrexate • Class: Folate Antimetabolite (Dihydrofolate Reductase & AICAR Transformylase Inhibitor); Anchor Conventional Synthetic DMARD (csDMARD) & Immunosuppressant

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THE INDIAN PHARMACIST — Educational Reference Sheet
Profile: Methotrexate (Low-Dose Weekly Immunomodulator / DMARD Regimen) ([7.12] | ID: TIP-MED-000114) • Last Reviewed: 2026-11-10
Source URL: https://theindianpharmacist.com/medicine/7-12-methotrexate-low-dose-weekly-immunomodulator-dmard-regimen/
Generic / Entity NameMethotrexate (Low-Dose Weekly Immunomodulator / DMARD Regimen) ([7.12])
Verified Indian Brands / RefGeneric Compendial Entry (No Commercial Brand Claimed)
Pharmacological ClassFolate Antimetabolite (Dihydrofolate Reductase & AICAR Transformylase Inhibitor); Anchor C
Available Dosage FormsOral Uncoated Tablets: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 15 mg; Subcutaneous/Parenteral Injection: 15 mg/mL, 25 mg/
Regulatory ClassificationSchedule H Prescription Drug • ISMP HIGH-ALERT MEDICATION (ONCE-WEEKLY DOSING)
Key Warning & Review DateContraindicated in chronic liver disease, alcoholism, or hepatic fibrosis.
Reviewed: 2026-11-10
Safety Matrix:⚖️ Legal Status: Schedule H Prescription Drug • ISMP HIGH-ALERT MEDIC🚨 Clinically High-Alert: Independent Dose & Route Verification Required☣️ Hazardous / Reproductive Precaution: Strict Handling & Contraception Protocol

1. Clinical & Scientific Overview

Methotrexate (Low-Dose Weekly Immunomodulator / DMARD Regimen) (TIP-MED-000114, Reference Code [7.12]) is classified under Pain, Inflammation, Rheumatology & Gout Medicines (Ch 07) as a Folate Antimetabolite (Dihydrofolate Reductase & AICAR Transformylase Inhibitor); Anchor Conventional Synthetic DMARD (csDMARD) & Immunosuppressant. Within the Indian regulatory and compendial framework, it is governed under Schedule H Prescription Drug • ISMP HIGH-ALERT MEDICATION (ONCE-WEEKLY DOSING).

Verified Indian Market Examples / Compendial Status:
Representative Indian Market Examples (Edition 2.7 Ch 07 [7.12], p. 84): Folitrax (Ipca), Neotrexate (GSK), Biotrexate, Mexate, Mext; Subcutaneous Prefilled Pen/Syringe: Metoject — Strengths & Forms: Oral Uncoated Tablets: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 15 mg; Subcutaneous/Parenteral Injection: 15 mg/mL, 25 mg/mL, 50 mg/2 mL
Representative Indian Market Examples (Edition 2.7 Ch 07 [7.12], p. 84): Folitrax (Ipca), Neotrexate (GSK), Biotrexate, Mexate, Mext; Subcutaneous Prefilled Pen/Syringe: Metoject — Strengths & Forms: Oral Uncoated Tablets: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 15 mg; Subcutaneous/Parenteral Injection: 15 mg/mL, 25 mg/mL, 50 mg/2 mL
Dosage Forms & Available Strengths:
Oral Uncoated Tablets: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 15 mg; Subcutaneous/Parenteral Injection: 15 mg/mL, 25 mg/mL, 50 mg/2 mL
Routes: Oral / Parenteral / Topical as specified by formulation

3. Mechanism of Action & Pharmacodynamics

Competitively and reversibly inhibits Dihydrofolate Reductase (DHFR), blocking reduction of dihydrofolate (FH2) to active tetrahydrofolate (FH4) and depleting thymidylate and purine synthesis (S-phase cell-cycle specific cytotoxicity in high-dose oncology). In low-dose weekly therapy for rheumatoid arthritis, intracellular Methotrexate polyglutamates inhibit AICAR transformylase (ATIC), elevating extracellular adenosine (acting on A2A receptors) to potently suppress T-cell and macrophage inflammation.

4. Therapeutic Indications & Evidence-Supported Uses

  • Rheumatoid arthritis (anchor first-line csDMARD), severe recalcitrant psoriasis, and psoriatic arthritis (STRICTLY ONCE WEEKLY)
  • Acute lymphoblastic leukaemia (ALL), choriocarcinoma, osteosarcoma, and non-Hodgkin lymphoma (oncology protocols)

🇮🇳 Jurisdiction & Indication Note: Indications and schedules reflect Indian compendial and regulatory records (CDSCO / Indian Pharmacopoeia & NFI / NLEM 2022). Where international reference labels (US FDA DailyMed / NCBI StatPearls) are cited for pharmacokinetic or mechanistic parameters, international approvals do not automatically imply CDSCO approval in India.

5. Educational Dosage Context, Formulations & Administration

Educational Dosing & Regimen Summary: Rheumatoid Arthritis / Psoriasis: 7.5 mg to 25 mg orally or subcutaneously ONCE WEEKLY on a single designated day of the week ( NEVER daily!), accompanied by Folic Acid 5 mg orally 1–2 times weekly (taken 24 hours after Methotrexate).

Administration & Meal Timing: Oral (STRICTLY ONCE WEEKLY for autoimmune diseases) or Subcutaneous / IM / IV / Intrathecal (preservative-free only).

6. Pharmacokinetics, Metabolism & Renal/Hepatic Adjustment

Absorption & Disposition:
Absorption, distribution, metabolism, and excretion follow class pharmacokinetic profile; verify patient renal/hepatic function.
Metabolism & Biotransformation:
Contraindicated in chronic liver disease, alcoholism, or hepatic fibrosis.
Elimination & Renal Adjustment:
Reduce dose by 50% if CrCl is 30–50 mL/min; CONTRAINDICATED if CrCl < 30 mL/min (precipitates fatal pancytopenia and mucositis).
Hepatic Impairment Considerations:
Contraindicated in chronic liver disease, alcoholism, or hepatic fibrosis.

7. Contraindications, Precautions & High-Risk Warnings

Contraindications & Red-Flag Precautions:
  • Pregnancy and breastfeeding (potent human teratogen — Category X; discontinue 3 months before conception)
  • Severe renal impairment (CrCl < 30 mL/min), chronic liver disease, or alcohol abuse
  • Pre-existing blood dyscrasias (leukopenia, thrombocytopenia, severe anaemia) or active severe infection

Key Clinical Precautions: Contraindicated in chronic liver disease, alcoholism, or hepatic fibrosis.

8. Adverse Effects Profile

Common & Mechanism-Related Adverse Effects:
  • Myelosuppression (leukopenia, thrombocytopenia, megaloblastic pancytopenia) and ulcerative oral mucositis/stomatitis
  • Hepatotoxicity (transaminitis, steatosis, progressive hepatic fibrosis/cirrhosis)
  • Acute hypersensitivity pneumonitis / interstitial pulmonary fibrosis (dry cough, dyspnoea)
Serious / Dose-Limiting Adverse Effects:
  • Crystalline nephropathy in high-dose oncology (prevented by IV hydration, urinary alkalinization with NaHCO3 to pH > 7.0, and Leucovorin rescue)

9. Major Drug–Drug, Drug–Food & Drug–Herb Interactions

  • Trimethoprim-Sulfamethoxazole (Cotrimoxazole): additive antifolate inhibition + tubular secretion blockade — CONTRAINDICATED (causes fatal acute pancytopenia)
  • NSAIDs (Diclofenac, Ibuprofen), Salicylates, & PPIs (Pantoprazole): inhibit renal OAT1/OAT3 tubular secretion and reduce GFR, elevating MTX levels
  • Penicillins (Amoxicillin, Piperacillin) & Probenecid: compete for renal tubular secretion and delay MTX clearance

10. Clinical Monitoring, Patient Counselling & Storage

Clinical & Laboratory Monitoring: Monitor clinical response, baseline renal/hepatic parameters, and relevant serum biomarkers.

Pharmacist Patient Counselling Points:

  • CRITICAL SAFETY ALERT: For rheumatoid arthritis or psoriasis, take Methotrexate ONLY ONCE A WEEK on the exact same named day (e.g., every Monday). Taking it daily by mistake is a life-threatening emergency causing bone marrow failure.
  • Take Folic Acid 5 mg on the day AFTER Methotrexate to prevent mouth ulcers and nausea.
  • Seek urgent medical evaluation if mouth sores, unexplained fever/sore throat, unusual bruising, or new dry cough/shortness of breath occurs.

Storage, Stability & Dispensing Safeguards: Store below 25–30°C protected from light; keep out of reach of children.

11. Visual Pharmacology & Mechanism Diagram (svg-v339-01-adme-12-step-journey)

THE 12-STEP ORAL DRUG JOURNEY THROUGH THE HUMAN BODY (LADME) Note: IV bolus enters Step 6 directly (F = 100%); Sublingual & Transdermal routes bypass Step 4–5 Portal First-Pass Metabolism 1. Oral Administration • Tablet / Capsule swallowed • Gastric emptying to duodenum pH 1.5–3.5 (Stomach) 2. Disintegration & Dissolution • Tablet breaks into granules • API dissolves in GI fluid Noyes-Whitney Dissolution Rate 3. GI Epithelial Absorption • Crosses intestinal villi • Passive / Active / P-gp efflux Small Intestine (Large Surface Area) 4. Portal Circulation • Mesenteric veins → Portal vein • Delivers blood to liver sinusoids Pre-systemic Venous Conduit 5. First-Pass Metabolism • Gut & hepatic CYP450 extraction • High: GTN, Propranolol, Morphine Determines Bioavailability (F = f_a × (1-E_H)) 6. Systemic Circulation • Hepatic vein → IVC → Heart • Unbound vs Albumin-bound drug Only FREE drug is active 7–8. Tissue Distribution (Vd) • Capillary permeation to organs • Blood-Brain & Placental barriers Vd = Dose / C_0 (L or L/kg) 9. Target Site of Action • Receptors (GPCR, Ion channel) • Enzymes & Carrier Transporters Pharmacodynamic Effect (E_max, EC50) 10. Hepatic Biotransformation • Phase I (CYP450 Oxidation/Hydrolysis) • Phase II (Glucuronidation/Sulfation) Converts lipophilic drug → hydrophilic metabolite 11. Renal & Biliary Elimination • Nephron: Filtration + Secretion − Reabsorption • Biliary excretion & Enterohepatic recycling Total Clearance CL_tot = CL_renal + CL_hepatic 12. Excretion from the Body • Urine (Primary polar metabolite route) • Bile/Faeces, Expired Air, Sweat, Milk Elimination Half-Life t1/2 = (0.693 × Vd) / CL
svg-v339-01-adme-12-step-journey — 8.1 Complete 12-Step Journey of an Orally Administered Drug (ADME): Figure 8.1: The 12-step physiological journey of a typical orally administered solid dosage form through Liberation, Absorption, Distribution, Metabolism, and Excretion (LADME). Note: Parenteral (IV), sublingual, and inhalational routes bypass gastrointestinal absorption and/or hepatic first-pass metabolism.

12. Authoritative References, Regulatory Sources & Editorial Disclaimer

Primary Compendial & Guideline Reference: Indian Pharmacopoeia (IP 2026) • NLEM 2022 (MoHFW) • CDSCO Approved Prescribing Information

Official Verification Portals: Indian Pharmacopoeia Commission (IPC) & National Formulary of India (NFI) • Central Drugs Standard Control Organization (CDSCO) • Ministry of Health & Family Welfare — NLEM 2022 • NCBI Bookshelf / StatPearls Pharmacology Reference • DailyMed (US FDA Official Prescribing Reference)

Last Medically & Pharmaceutically Reviewed: 2026-11-10 • Verification Status: VERIFIED_EDUCATIONAL_CONTENT

Educational & Clinical Disclaimer: This reference profile is published solely for pharmacy education, academic study, and professional clinical reference. It does not substitute for patient-specific clinical judgement, qualified specialist oncology/medical supervision, or official CDSCO/IP prescribing information. Never self-medicate with prescription, Schedule H/H1/X, NDPS, or oncology medicines.

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Educational Reference Notice: This printout from THE INDIAN PHARMACIST (https://theindianpharmacist.com/medicine/7-12-methotrexate-low-dose-weekly-immunomodulator-dmard-regimen/, Last Reviewed: 2026-11-10) is an educational reference sheet for students and healthcare learners. It is NOT an official prescribing guideline or patient-specific treatment order.