Baby Safety / Compounds / Busulfan

Is Busulfan safe for babies and kids?

Extreme risk for kids

(Babies-specific data is limited; this page draws from human pregnant context.) Busulfan is a known teratogen and reproductive toxicant classified as FDA Pregnancy Category D (positive evidence of fetal risk). Administration of busulfan during pregnancy, particularly in the first trimester, is associated with severe fetal malformations and growth retardation. Animal reproductive toxicity is extensive across multiple species. The clinical dilemma of managing CML diagnosed during pregnancy has been extensively documented — before imatinib, pregnant women with CML had extremely limited safe treatment options, as busulfan was the only effective agent and carried severe teratogenic risk. Imatinib also has teratogenic potential (Category D) but with a different malformation profile; current guidelines recommend hydroxyurea (lower teratogenic risk) as cytoreductive therapy during the first trimester, with consideration of leukopheresis in extreme cases, followed by imatinib after the first trimester. Busulfan must be avoided throughout pregnancy unless no safer alternative exists and maternal survival is at immediate risk. Busulfan also causes premature ovarian insufficiency and azoospermia — fertility is rarely preserved after busulfan-containing conditioning regimens, and gonadal protection is generally impossible given the systemic nature of conditioning.

What is busulfan?

The IUPAC name is 4-methylsulfonyloxybutyl methanesulfonate.

Also known as: 4-methylsulfonyloxybutyl methanesulfonate, Myleran, Busulphan, Sulphabutin.

IUPAC name
4-methylsulfonyloxybutyl methanesulfonate
CAS number
55-98-1
Molecular formula
C6H14O6S2
Molecular weight
246.3 g/mol
SMILES
CS(=O)(=O)OCCCCOS(=O)(=O)C
PubChem CID
2478

Risk for babies

Extreme risk

Busulfan is a known teratogen and reproductive toxicant classified as FDA Pregnancy Category D (positive evidence of fetal risk). Administration of busulfan during pregnancy, particularly in the first trimester, is associated with severe fetal malformations and growth retardation. Animal reproductive toxicity is extensive across multiple species. The clinical dilemma of managing CML diagnosed during pregnancy has been extensively documented — before imatinib, pregnant women with CML had extremely limited safe treatment options, as busulfan was the only effective agent and carried severe teratogenic risk. Imatinib also has teratogenic potential (Category D) but with a different malformation profile; current guidelines recommend hydroxyurea (lower teratogenic risk) as cytoreductive therapy during the first trimester, with consideration of leukopheresis in extreme cases, followed by imatinib after the first trimester. Busulfan must be avoided throughout pregnancy unless no safer alternative exists and maternal survival is at immediate risk. Busulfan also causes premature ovarian insufficiency and azoospermia — fertility is rarely preserved after busulfan-containing conditioning regimens, and gonadal protection is generally impossible given the systemic nature of conditioning.

Risk for pregnant and nursing people

Extreme risk

Busulfan is a known teratogen and reproductive toxicant classified as FDA Pregnancy Category D (positive evidence of fetal risk). Administration of busulfan during pregnancy, particularly in the first trimester, is associated with severe fetal malformations and growth retardation. Animal reproductive toxicity is extensive across multiple species. The clinical dilemma of managing CML diagnosed during pregnancy has been extensively documented — before imatinib, pregnant women with CML had extremely limited safe treatment options, as busulfan was the only effective agent and carried severe teratogenic risk. Imatinib also has teratogenic potential (Category D) but with a different malformation profile; current guidelines recommend hydroxyurea (lower teratogenic risk) as cytoreductive therapy during the first trimester, with consideration of leukopheresis in extreme cases, followed by imatinib after the first trimester. Busulfan must be avoided throughout pregnancy unless no safer alternative exists and maternal survival is at immediate risk. Busulfan also causes premature ovarian insufficiency and azoospermia — fertility is rarely preserved after busulfan-containing conditioning regimens, and gonadal protection is generally impossible given the systemic nature of conditioning.

Regulatory consensus

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

AgencyYearClassificationNotes
IARC2012Group 1
US EPA2000carcinogenic to humans
EPA CTX / NTP RoC—Known Human Carcinogen
EPA CTX / IARC—Group 1 - Carcinogenic to humans
EPA CTX / CalEPA—Known human carcinogen
EPA CTX / Genetox—Genotoxicity: positive (Ames: positive, 24 positive / 0 negative reports)
EPA CTX / Genetox—Genotoxicity: positive (Ames: positive, 24 positive / 0 negative reports)
EPA CTX / Skin-Eye—Skin Irritation: SkinIrr2 (score: high)

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 busulfan

  • 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 Busulfan:

  • Safer process chemistry; Green chemistry alternatives; Exposure controls
    Trade-offs: Requires R&D investment to redesign synthesis routes; may reduce yield or throughput initially; long-term benefits include reduced waste treatment costs, regulatory compliance, and worker safety; 12 Principles of Green Chemistry framework available.
    Relative cost: 2-5×

Frequently asked questions

What products contain busulfan?

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

Why do regulators disagree about busulfan?

Busulfan has been classified by 8 agencies including IARC, US EPA, EPA CTX / NTP RoC, EPA CTX / IARC, EPA CTX / CalEPA, 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 Busulfan in the baby app

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

Open in baby View raw API data

Sources (2)
  1. IARC Monographs Volume 100A: Pharmaceuticals — Busulfan Group 1; AML in CML/Polycythemia Vera Patients; Alkylsulfonate DNA Alkylation; Busulfan Lung Interstitial Pneumonitis; Teratogenicity; Bu/Cy Transplant Conditioning (2012) — iarc_monograph
  2. US EPA Busulfan: Carcinogenic to Humans; NIOSH Hazardous Drug; FDA Pregnancy Category D Teratogen; CML Historical Treatment; Imatinib Replacement; Therapeutic Drug Monitoring; Hospital Wastewater Excretion (2000) — 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 →