Baby Safety / Compounds / Phenytoin

Is Phenytoin safe for babies and kids?

Context-dependent 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 Phenytoin poses heightened risk.

What is phenytoin?

Also known as: 5,5-DIPHENYLHYDANTOIN, Diphenylhydantoin, 5,5-diphenylimidazolidine-2,4-dione, Phenytoine.

CAS number
57-41-0
Molecular formula
C15H12N2O2
Molecular weight
252.27 g/mol
SMILES
C1=CC=C(C=C1)C2(C(=O)NC(=O)N2)C3=CC=CC=C3
PubChem CID
1775

Risk for babies

Context-dependent

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

Context-dependent

Regulatory consensus

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

AgencyYearClassificationNotes
EDC Assessment—Suspected endocrine disruptor
Regulatory Framework—Regulated as pharmaceutical (FDA/EMA); not typically classified under industrial chemical regulations

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 phenytoin

  • Consumer Products — antiepileptic medication

Safer alternatives

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

  • 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 phenytoin 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 Phenytoin poses heightened risk.

What products contain phenytoin?

Phenytoin appears in: antiepileptic medication (Consumer products).

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

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.

See Phenytoin in the baby app

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

Open in baby View raw API data

Sources (1)
  1. PubChem (2026) — database

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 →