Baby Safety / Compounds / Methotrexate

Is Methotrexate safe for babies and kids?

Very high risk for kids

Infants have immature drug-metabolizing enzymes (CYP450 ontogeny), reduced renal clearance, and different volume of distribution. Accidental exposure or breast milk transfer of Methotrexate poses heightened risk.

What is methotrexate?

The IUPAC name is (2S)-2-[[4-[(2,4-diaminopteridin-6-yl)methyl-methylamino]benzoyl]amino]pentanedioic acid.

Also known as: (2S)-2-[[4-[(2,4-diaminopteridin-6-yl)methyl-methylamino]benzoyl]amino]pentanedioic acid, Rheumatrex, Amethopterin, Metatrexan.

IUPAC name
(2S)-2-[[4-[(2,4-diaminopteridin-6-yl)methyl-methylamino]benzoyl]amino]pentanedioic acid
CAS number
59-05-2
Molecular formula
C20H22N8O5
Molecular weight
454.4 g/mol
SMILES
CN(CC1=CN=C2C(=N1)C(=NC(=N2)N)N)C3=CC=C(C=C3)C(=O)NC(CCC(=O)O)C(=O)O
PubChem CID
126941

Risk for babies

Very high risk

Infants have immature drug-metabolizing enzymes (CYP450 ontogeny), reduced renal clearance, and different volume of distribution. Accidental exposure or breast milk transfer of Methotrexate poses heightened risk.

Neonates and infants up to 12 months have incomplete blood-brain barrier development, immature Phase I/II metabolic enzymes (particularly CYP3A4, UGT1A1), and higher gastrointestinal permeability. Equivalent doses produce higher internal concentrations and longer residence times.

What to do: Minimize infant exposure through source control. For breastfeeding mothers: reduce maternal exposure. For formula-fed infants: use certified low-migration bottles and verified water sources. Consult pediatrician regarding any concerns.

Risk for pregnant and nursing people

High risk

Methotrexate poses pregnancy risk through potential teratogenicity, altered pharmacokinetics (increased blood volume, changed CYP activity), and placental transfer. FDA pregnancy category should be evaluated.

Suspected reproductive toxicant (GHS H361) or suspected endocrine disruptor. Precautionary approach warranted. Animal studies or limited human data suggest developmental toxicity potential.

What to do: Minimize exposure during pregnancy and lactation. Consult healthcare provider regarding specific risks. Consider alternative products with lower hazard profiles.

Regulatory consensus

4 regulatory and scientific bodies have classified Methotrexate. The classifications differ — that's the data.

AgencyYearClassificationNotes
IARC2012Group 1IARC Group 1 classification for methotrexate based on sufficient evidence of carcinogenicity in humans — specifically, immunosuppression-related lymphomas (including non-Hodgkin lymphoma) associated with long-term immunosuppressive therapy. Methotrexate at low doses used in autoimmune disease (rheumatoid arthritis, psoriasis) is associated with increased lymphoma risk primarily through immunosuppression-mediated mechanisms; some lymphomas regress on drug withdrawal. At higher doses used in oncology, the carcinogenic risk must be weighed against the therapeutic benefit for life-threatening malignancies.
EPA CTX / IARC—Group 3 - Not classifiable as to its carcinogenicity to humans
EPA CTX / Genetox—Genotoxicity: positive (Ames: positive, 16 positive / 3 negative reports)
EPA CTX / Genetox—Genotoxicity: positive (Ames: positive, 16 positive / 3 negative reports)

Regulators apply different standards of evidence — animal-data weighting, exposure-pattern assumptions, epidemiological power thresholds — which is why two scientific bodies can review the same data and reach different conclusions. The disagreement is the data.

Where kids encounter methotrexate

  • Industrial Facilities — Manufacturing plants, Chemical storage areas, Waste treatment sites
  • Occupational Environments — Factories, Warehouses, Transportation vehicles

Safer alternatives

Lower-risk approaches that achieve a similar outcome to Methotrexate:

  • Alternative drug class; Non-pharmacological therapy; Lowest effective dose
    Trade-offs: Direct chemical substitution requires verification that the replacement does not introduce new hazards (regrettable substitution). Conduct full hazard assessment of proposed alternative before adoption.
    Relative cost: 1.2-2×

Frequently asked questions

Is methotrexate safe for kids?

Infants have immature drug-metabolizing enzymes (CYP450 ontogeny), reduced renal clearance, and different volume of distribution. Accidental exposure or breast milk transfer of Methotrexate poses heightened risk.

What products contain methotrexate?

Methotrexate appears in: Manufacturing plants (Industrial facilities); Chemical storage areas (Industrial facilities); Factories (Occupational environments); Warehouses (Occupational environments).

What should I do if my child is exposed to methotrexate?

Minimize infant exposure through source control. For breastfeeding mothers: reduce maternal exposure. For formula-fed infants: use certified low-migration bottles and verified water sources. Consult pediatrician regarding any concerns.

Why do regulators disagree about methotrexate?

Methotrexate has been classified by 4 agencies including IARC, EPA CTX / IARC, EPA CTX / Genetox, EPA CTX / Genetox, with differing conclusions. Regulators apply different standards of evidence (animal data weighting, exposure-pattern assumptions, epidemiological power thresholds), which is why two scientific bodies can review the same data and reach different conclusions. See the regulatory consensus table on this page for the full picture.

See Methotrexate in the baby app

Look up products containing methotrexate, compare to alternatives, and explore the full data record.

Open in baby View raw API data

Sources (5)
  1. IARC Monographs Volume 100A: Pharmaceuticals — Methotrexate, Group 1 Classification (Immunosuppression-Associated Lymphomas) (2012) — regulatory
  2. US FDA: Methotrexate Prescribing Information — Indications, Dosing, Black Box Warnings (Myelosuppression, Hepatotoxicity, Pulmonary Toxicity, Teratogenicity), and Leucovorin Rescue (2022) — regulatory
  3. ASPCA Animal Poison Control Center: Methotrexate Toxicosis in Dogs and Cats — Emergency Management and Leucovorin Rescue Protocol (2023) — veterinary
  4. Plumb's Veterinary Drug Handbook (10th ed.) — Methotrexate: Veterinary Oncology Use and Toxicity Management (2023) — veterinary
  5. NIOSH: Safe Handling of Hazardous Drugs — Antineoplastic Agents, PPE Requirements, Engineering Controls, and Pharmaceutical Waste Disposal (2016) — regulatory

Reference data, not professional advice. Aggregates publicly available regulatory and scientific data; not a substitute for veterinary, medical, legal, or regulatory advice. Why we built ALETHEIA →