Drug · FAERS side-effect profile with label screen
Busulfan side effects: what 15,644 FDA adverse event reports show
Who reports
15,644 reports · 95% serious · 4,592 with death outcome · 43% female
openFDA FAERS counts, all years, deduplication not applied
Used for
Busulfan Injection is indicated for use in combination with cyclophosphamide as a conditioning regimen prior to allogeneic hematopoietic progenitor cell transplantation for chronic myelogenous leukemia. Busulfan Injection is an alkylating drug indicate.
FDA label, Indications and Usage
What it is
Busulfan is a bifunctional alkylating agent known chemically as 1,4-butanediol, dimethanesulfonate.
FDA label, Description section
Boxed warning
MYELOSUPPRESSION Busulfan Injection causes severe and prolonged myelosuppression at the recommended dosage. Hematopoietic progenitor cell transplantation is required to prevent potentially fatal complications of the prolonged myelosuppression [see Warnings and Precautions ( 5.1 )] .
FDA label
How to read this page. FAERS is a spontaneous-reporting system: counts are not incidence rates and a signal is not proof of causation.
Each reaction below is run through an automated screen — is the term in the FDA label (known), in the indications (the disease being treated), an administrative/coding term, or none of these (unlabeled)?
That screen is mechanical text matching, not a causality assessment. The 30 hand-written Bradford Hill assessments are on the causality assessment page. Not medical advice.
Causality screen of the 40 strongest signals
Labeled adverse reaction 1Labeled (related wording) 18Likely indication confounding 1Not in label — unassessed 20
What the badges mean
- Labeled adverse reaction The exact term appears in the label's warnings or adverse-reactions sections: a known, expected effect. The FAERS signal confirms the label rather than discovering anything.
- Labeled (related wording) The label describes this effect under different wording (e.g. 'neutropenia' for 'neutrophil count decreased'). Treated as known.
- Likely indication confounding The term appears in the label's indications: reports probably describe the disease being treated (or its progression), not a drug effect. Classic confounding by indication.
- Not in label — unassessed Not found in the label text, not an artifact pattern. This is a genuine candidate for a formal causality assessment (Bradford Hill / WHO-UMC); it has NOT had one here.
Strongest disproportionality signals
Flagged terms (PRR ≥ 2, χ² ≥ 4, n ≥ 10), ranked by PRR; infinite PRRs (no comparator reports) excluded. The EBGM column is a second, shrinkage-based estimate (MGPS) with its 5th percentile EB05 and the BCPNN IC025; a pair flagged by PRR alone is marked PRR-only and should be read as fragile. The strata column recomputes the PRR on serious reports only and flags pairs whose reports are unusually skewed by sex or come mostly from consumers rather than clinicians. 984 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.
Show:
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Rhizobium radiobacter bacteraemia | 13 | 8,591.8 1,939.0–38,070.8ROR 8,598.9 · χ² 13,765 / p <1e-300 | 425.7 EB05 264.7 · IC025 +3.8 3/3 methods agree | Not in label — unassessed | serious n=13 | no trial arm names this drug |
| Actinomycotic sepsis | 18 | 3,398.9 1,419.8–8,136.6ROR 3,402.9 · χ² 16,182 / p <1e-300 | 472.2 EB05 316.0 · IC025 +4.4 3/3 methods agree | Not in label — unassessed | serious n=18 | no trial arm names this drug |
| Cytomegalovirus urinary tract infection | 20 | 2,403.3 1,151.7–5,014.9ROR 2,406.4 · χ² 16,199 / p <1e-300 | 468.9 EB05 320.5 · IC025 +4.5 3/3 methods agree | Labeled (related wording) related wording | serious n=20 · 100% clinician | no trial arm names this drug |
| Ovarian atrophy | 27 | 626.1 396.2–989.5ROR 627.2 · χ² 11,014 / p <1e-300 | 326.7 EB05 235.8 · IC025 +5.0 3/3 methods agree | Not in label — unassessed | serious n=27 · ♀ 100% (drug 43%) · 100% clinician | no trial arm names this drug |
| Viral haemorrhagic cystitis | 198 | 524.5 445.2–617.9ROR 531.2 · χ² 73,692 / p <1e-300 | 362.6 EB05 322.1 · IC025 +7.4 3/3 methods agree | Labeled (related wording) related wording | serious n=198 · 95% clinician | no trial arm names this drug |
| Cystitis viral | 97 | 459.6 365.0–578.7ROR 462.4 · χ² 32,594 / p <1e-300 | 319.7 EB05 269.8 · IC025 +6.6 3/3 methods agree | Labeled (related wording) related wording | serious n=97 · 94% clinician | no trial arm names this drug |
| Disseminated toxoplasmosis | 29 | 451.0 295.9–687.2ROR 451.8 · χ² 9,375 / p <1e-300 | 275.4 EB05 201.1 · IC025 +5.0 3/3 methods agree | Not in label — unassessed | serious n=29 · 93% clinician | no trial arm names this drug |
| Autoimmune lymphoproliferative syndrome | 15 | 450.6 250.8–809.5ROR 451.0 · χ² 4,689 / p <1e-300 | 235.6 EB05 151.6 · IC025 +4.0 3/3 methods agree | Not in label — unassessed | serious n=15 | no trial arm names this drug |
| Bronchiolitis obliterans syndrome | 39 | 402.7 281.5–576.2ROR 403.7 · χ² 11,673 / p <1e-300 | 268.3 EB05 204.8 · IC025 +5.4 3/3 methods agree | Not in label — unassessed | serious n=39 · ♀ 76% (drug 43%) · 100% clinician | no trial arm names this drug |
| Primary hypogonadism | 36 | 399.9 275.5–580.4ROR 400.8 · χ² 10,693 / p <1e-300 | 264.2 EB05 199.4 · IC025 +5.3 3/3 methods agree | Not in label — unassessed | serious n=34 · ♀ 83% (drug 43%) · 97% clinician | no trial arm names this drug |
| Idiopathic pneumonia syndrome | 64 | 367.8 278.9–485.0ROR 369.3 · χ² 18,030 / p <1e-300 | 265.2 EB05 215.0 · IC025 +6.1 3/3 methods agree | Labeled (related wording) related wording | serious n=64 · ♀ 72% (drug 43%) · 95% clinician | no trial arm names this drug |
| Acute graft versus host disease in skin | 585 | 361.5 330.4–395.6ROR 375.5 · χ² 164,884 / p <1e-300 | 281.5 EB05 262.8 · IC025 +7.7 3/3 methods agree | Labeled (related wording) related wording | serious n=585 · 99% clinician | no trial arm names this drug |
| Venoocclusive disease | 525 | 356.1 323.8–391.6ROR 368.4 · χ² 146,173 / p <1e-300 | 277.9 EB05 258.5 · IC025 +7.6 3/3 methods agree | Not in label — unassessed | serious n=525 | no trial arm names this drug |
| Chimerism | 18 | 339.9 202.5–570.4ROR 340.3 · χ² 4,572 / p <1e-300 | 210.4 EB05 140.8 · IC025 +4.2 3/3 methods agree | Not in label — unassessed | serious n=18 | no trial arm names this drug |
| Retinopathy haemorrhagic | 13 | 324.2 176.8–594.6ROR 324.5 · χ² 3,109 / p <1e-300 | 188.8 EB05 117.4 · IC025 +3.7 3/3 methods agree | Not in label — unassessed | serious n=13 | no trial arm names this drug |
| Chronic graft versus host disease in intestine | 36 | 321.5 223.4–462.6ROR 322.3 · χ² 8,996 / p <1e-300 | 227.6 EB05 171.8 · IC025 +5.3 3/3 methods agree | Not in label — unassessed | serious n=36 · 100% clinician | no trial arm names this drug |
| Engraft failure | 55 | 320.3 238.6–429.8ROR 321.4 · χ² 13,835 / p <1e-300 | 236.8 EB05 188.8 · IC025 +5.8 3/3 methods agree | Labeled (related wording) related wording | serious n=55 · 98% clinician | no trial arm names this drug |
| Heart failure with midrange ejection fraction | 10 | 314.7 157.9–627.1ROR 314.9 · χ² 2,279 / p <1e-300 | 171.7 EB05 99.7 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious n=10 | no trial arm names this drug |
| Acute graft versus host disease in intestine | 255 | 298.3 260.6–341.4ROR 303.2 · χ² 61,404 / p <1e-300 | 239.2 EB05 215.5 · IC025 +7.2 3/3 methods agree | Not in label — unassessed | serious n=255 · 100% clinician | no trial arm names this drug |
| Acute graft versus host disease | 825 | 292.1 271.4–314.5ROR 308.3 · χ² 195,835 / p <1e-300 | 238.1 EB05 224.8 · IC025 +7.6 3/3 methods agree | Labeled (related wording) related wording | serious n=823 · 96% clinician | no trial arm names this drug |
| Venoocclusive liver disease | 875 | 290.7 270.6–312.2ROR 307.8 · χ² 206,869 / p <1e-300 | 237.2 EB05 224.3 · IC025 +7.6 3/3 methods agree | Not in label — unassessed | serious n=873 · 95% clinician | no trial arm names this drug |
| Chronic graft versus host disease | 645 | 289.3 266.1–314.6ROR 301.7 · χ² 151,825 / p <1e-300 | 235.9 EB05 221.0 · IC025 +7.5 3/3 methods agree | Labeled (related wording) related wording | serious n=645 · 98% clinician | no trial arm names this drug |
| Hyperfibrinogenaemia | 12 | 288.4 154.5–538.4ROR 288.6 · χ² 2,590 / p <1e-300 | 172.4 EB05 105.1 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | serious n=12 | no trial arm names this drug |
| Viruria | 18 | 276.7 166.5–459.7ROR 277.0 · χ² 3,863 / p <1e-300 | 184.4 EB05 123.4 · IC025 +4.2 3/3 methods agree | Not in label — unassessed | serious n=18 | no trial arm names this drug |
| Retinitis viral | 20 | 269.8 166.8–436.2ROR 270.1 · χ² 4,227 / p <1e-300 | 184.9 EB05 126.4 · IC025 +4.4 3/3 methods agree | Not in label — unassessed | serious n=20 · ♀ 100% (drug 43%) · 100% clinician | no trial arm names this drug |
| Graft versus host disease in skin | 361 | 263.3 235.5–294.5ROR 269.5 · χ² 78,461 / p <1e-300 | 217.2 EB05 199.1 · IC025 +7.2 3/3 methods agree | Labeled (related wording) related wording | serious n=360 · 97% clinician | no trial arm names this drug |
| Acute graft versus host disease in liver | 117 | 259.9 213.3–316.7ROR 261.9 · χ² 25,003 / p <1e-300 | 209.9 EB05 179.9 · IC025 +6.5 3/3 methods agree | Labeled (related wording) related wording | serious n=117 · 97% clinician | no trial arm names this drug |
| Graft versus host disease in gastrointestinal tract | 343 | 257.9 230.0–289.2ROR 263.7 · χ² 73,236 / p <1e-300 | 213.4 EB05 195.1 · IC025 +7.2 3/3 methods agree | Labeled (related wording) related wording | serious n=343 · 96% clinician | no trial arm names this drug |
| Engraftment syndrome | 90 | 242.8 194.0–303.8ROR 244.2 · χ² 18,105 / p <1e-300 | 196.7 EB05 164.9 · IC025 +6.2 3/3 methods agree | Labeled (related wording) related wording | serious n=89 · 98% clinician | no trial arm names this drug |
| Epstein-barr virus infection reactivation | 191 | 238.6 204.7–278.2ROR 241.6 · χ² 38,086 / p <1e-300 | 198.3 EB05 175.8 · IC025 +6.8 3/3 methods agree | Not in label — unassessed | serious n=190 · 97% clinician | no trial arm names this drug |
| Chronic graft versus host disease in skin | 134 | 231.5 192.8–278.0ROR 233.5 · χ² 25,978 / p <1e-300 | 191.8 EB05 166.1 · IC025 +6.5 3/3 methods agree | Labeled (related wording) related wording | serious n=134 · 98% clinician | no trial arm names this drug |
| Chronic graft versus host disease in eye | 28 | 221.6 148.6–330.6ROR 222.0 · χ² 5,079 / p <1e-300 | 168.3 EB05 122.2 · IC025 +4.8 3/3 methods agree | Labeled (related wording) related wording | serious n=28 · 100% clinician | no trial arm names this drug |
| Cytomegalovirus infection reactivation | 595 | 217.4 199.6–236.7ROR 225.9 · χ² 109,891 / p <1e-300 | 185.7 EB05 173.5 · IC025 +7.2 3/3 methods agree | Labeled (related wording) related wording | serious n=592 · 98% clinician | no trial arm names this drug |
| Bone marrow transplant rejection | 31 | 216.8 148.3–316.9ROR 217.2 · χ² 5,537 / p <1e-300 | 167.3 EB05 123.5 · IC025 +5.0 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=31 · 97% clinician | no trial arm names this drug |
| Upper respiratory fungal infection | 26 | 209.6 138.6–316.8ROR 209.9 · χ² 4,480 / p <1e-300 | 160.0 EB05 114.7 · IC025 +4.7 3/3 methods agree | Labeled (related wording) related wording | serious n=26 · ♀ 100% (drug 43%) | no trial arm names this drug |
| Chronic graft versus host disease in liver | 48 | 206.7 152.5–280.0ROR 207.3 · χ² 8,319 / p <1e-300 | 167.1 EB05 131.0 · IC025 +5.5 3/3 methods agree | Labeled (related wording) related wording | serious n=48 · ♀ 15% (drug 43%) · 98% clinician | no trial arm names this drug |
| Short stature | 34 | 200.6 139.9–287.7ROR 201.1 · χ² 5,692 / p <1e-300 | 158.9 EB05 118.9 · IC025 +5.1 3/3 methods agree | Not in label — unassessed | serious n=34 · ♀ 0% (drug 43%) · 91% clinician | no trial arm names this drug |
| Graft versus host disease | 914 | 194.0 181.4–207.6ROR 206.0 · χ² 152,949 / p <1e-300 | 168.7 EB05 159.8 · IC025 +7.2 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 103.1 · 96% clinician | no trial arm names this drug |
| Complications of bone marrow transplant | 46 | 193.0 141.7–262.9ROR 193.6 · χ² 7,501 / p <1e-300 | 157.6 EB05 123.0 · IC025 +5.4 3/3 methods agree | Labeled (related wording) related wording | serious n=46 · 100% clinician | no trial arm names this drug |
| Herpes zoster infection neurological | 20 | 190.2 119.0–303.8ROR 190.4 · χ² 3,127 / p <1e-300 | 143.8 EB05 98.3 · IC025 +4.3 3/3 methods agree | Not in label — unassessed | serious n=20 · 90% clinician | no trial arm names this drug |
Trial evidence (ClinicalTrials.gov)
ClinicalTrials.gov returned results-bearing trials mentioning Busulfan only as a background or rescue medication (NCT00049517, NCT00416598); no trial listing it as the tested intervention was cached, so no trial cross-check is shown.
Most frequently reported reactions
By raw co-report count, regardless of disproportionality. Common terms here are often the illness itself or generic outcomes.
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Off label use (used outside approved label) | 2,019 | 3.1 3.0–3.3ROR 3.4 · χ² 3,031 / p <1e-300 | 3.1 EB05 3.0 · IC025 +1.6 3/3 methods agree | Reporting / coding artifact | serious PRR 3.4 · 93% clinician | no trial arm names this drug |
| Product use in unapproved indication | 1,723 | 9.5 9.1–10.0ROR 10.6 · χ² 13,181 / p <1e-300 | 9.4 EB05 9.1 · IC025 +3.2 3/3 methods agree | Reporting / coding artifact | serious PRR 9.4 · 97% clinician | no trial arm names this drug |
| Mucosal inflammation | 1,113 | 59.8 56.4–63.4ROR 64.3 · χ² 61,572 / p <1e-300 | 57.2 EB05 54.4 · IC025 +5.7 3/3 methods agree | Labeled (related wording) related wording | serious PRR 36.0 · 95% clinician | no trial arm names this drug |
| Drug ineffective (drug did not work) | 1,076 | 1.1 1.0–1.2ROR 1.1 · χ² 9 / p 0.001 | 1.1 EB05 1.0 · IC025 +0.0 | Reporting / coding artifact | serious PRR 1.9 · 97% clinician | no trial arm names this drug |
| Graft versus host disease | 914 | 194.0 181.4–207.6ROR 206.0 · χ² 152,949 / p <1e-300 | 168.7 EB05 159.8 · IC025 +7.2 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 103.1 · 96% clinician | no trial arm names this drug |
| Venoocclusive liver disease | 875 | 290.7 270.6–312.2ROR 307.8 · χ² 206,869 / p <1e-300 | 237.2 EB05 224.3 · IC025 +7.6 3/3 methods agree | Not in label — unassessed | serious n=873 · 95% clinician | no trial arm names this drug |
| Cytomegalovirus infection | 873 | 74.2 69.5–79.3ROR 78.6 · χ² 59,702 / p <1e-300 | 70.2 EB05 66.4 · IC025 +6.0 3/3 methods agree | Labeled (related wording) related wording | serious PRR 43.0 · 96% clinician | no trial arm names this drug |
| Febrile neutropenia | 863 | 17.7 16.6–18.9ROR 18.7 · χ² 13,435 / p <1e-300 | 17.5 EB05 16.5 · IC025 +4.0 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 10.6 · 95% clinician | no trial arm names this drug |
| Acute graft versus host disease | 825 | 292.1 271.4–314.5ROR 308.3 · χ² 195,835 / p <1e-300 | 238.1 EB05 224.8 · IC025 +7.6 3/3 methods agree | Labeled (related wording) related wording | serious n=823 · 96% clinician | no trial arm names this drug |
| Pyrexia (fever) | 816 | 3.2 3.0–3.4ROR 3.3 · χ² 1,223 / p 3e-268 | 3.2 EB05 3.0 · IC025 +1.5 3/3 methods agree | Labeled (related wording) related wording | serious PRR 2.4 · 95% clinician | no trial arm names this drug |
| Chronic graft versus host disease | 645 | 289.3 266.1–314.6ROR 301.7 · χ² 151,825 / p <1e-300 | 235.9 EB05 221.0 · IC025 +7.5 3/3 methods agree | Labeled (related wording) related wording | serious n=645 · 98% clinician | no trial arm names this drug |
| Cytomegalovirus infection reactivation | 595 | 217.4 199.6–236.7ROR 225.9 · χ² 109,891 / p <1e-300 | 185.7 EB05 173.5 · IC025 +7.2 3/3 methods agree | Labeled (related wording) related wording | serious n=592 · 98% clinician | no trial arm names this drug |
| Acute graft versus host disease in skin | 585 | 361.5 330.4–395.6ROR 375.5 · χ² 164,884 / p <1e-300 | 281.5 EB05 262.8 · IC025 +7.7 3/3 methods agree | Labeled (related wording) related wording | serious n=585 · 99% clinician | no trial arm names this drug |
| Thrombocytopenia (low platelets) | 566 | 6.8 6.3–7.4ROR 7.1 · χ² 2,814 / p <1e-300 | 6.8 EB05 6.3 · IC025 +2.6 3/3 methods agree | Labeled — boxed warning exact term | serious PRR 4.2 · 95% clinician | no trial arm names this drug |
| Infection | 533 | 5.0 4.6–5.4ROR 5.1 · χ² 1,692 / p <1e-300 | 4.9 EB05 4.6 · IC025 +2.2 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 3.8 · 96% clinician | no trial arm names this drug |
Unlabeled candidate signals
These flagged terms were not found in the FDA label text and do not match an artifact pattern. They are the pairs that would merit a structured assessment (temporality, dose-response, biological plausibility, consistency across databases, trial or cohort evidence). The screen has not done that; string-matching misses label wording, and a strong PRR can still be stimulated reporting, co-medication, or the disease itself.
- Ovarian atrophy — n=27, PRR 626.1
- Disseminated toxoplasmosis — n=29, PRR 451.0
- Bronchiolitis obliterans syndrome — n=39, PRR 402.7
- Primary hypogonadism — n=36, PRR 399.9
- Venoocclusive disease — n=525, PRR 356.1
- Chronic graft versus host disease in intestine — n=36, PRR 321.5
- Acute graft versus host disease in intestine — n=255, PRR 298.3
- Venoocclusive liver disease — n=875, PRR 290.7
- Retinitis viral — n=20, PRR 269.8
- Epstein-barr virus infection reactivation — n=191, PRR 238.6
Want to assess one of these properly? The runbook describes the Bradford Hill / trial-evidence workflow used on the assessment page, and handoff_top1000_signals.csv lists the strongest unassessed pairs across all drugs.
Common questions
What are the most reported side effects of Busulfan?
In FDA FAERS, the most frequently co-reported reaction terms for Busulfan are mucosal inflammation, graft versus host disease, venoocclusive liver disease, cytomegalovirus infection, febrile neutropenia, acute graft versus host disease. These are report counts, not rates: FAERS has no denominator, reporting is voluntary and uneven, and a term can be reported because of the illness being treated rather than the drug.
Does Busulfan have an FDA boxed warning?
Yes. The current FDA label carries a boxed warning: MYELOSUPPRESSION Busulfan Injection causes severe and prolonged myelosuppression at the recommended dosage. Hematopoietic progenitor cell transplantation is required to prevent potentially fatal complications of the prolonged myelosuppression [see Warnings and Precautions ( 5.1 )] .
Do FAERS signals prove that Busulfan causes these side effects?
No. A disproportionality signal (PRR, ROR) means a reaction is reported more often with this drug than with others in the database. That can reflect a real effect, but also the disease being treated, stimulated reporting after news or litigation, co-medications, or how reports are coded. Causality needs temporality, dose-response, biological plausibility, consistency across data sources and, ideally, trial or cohort evidence. This page screens each term against the FDA label and ClinicalTrials.gov results; it does not establish causation.
Sources & methods
- FDA label via openFDA (set ID 086a715e-4958-4bb5-9ebd-86171e6b6203, effective 20260729; matched on
openfda.generic_name.exact:"BUSULFAN") - Bayesian shrinkage measures computed offline over all 1,317,300 cached pairs: BCPNN information component (IC, with Norén closed-form IC025) and MGPS empirical-Bayes geometric mean (EBGM, EB05) with a two-component gamma prior fitted by maximum marginal likelihood (α₁=0.57, β₁=0.02, α₂=1.42, β₂=0.70, w=0.17); unstratified
- FAERS pair statistics from the OpenPV build of 2026-09-14 (openFDA
count=aggregation, fieldpatient.drug.openfda.generic_name.exact, 1,024 reaction terms, min 3 co-reports); PRR/ROR with 95% CI, chi-square with Yates correction - Serious-only and stratified counts (serious:1, patient.patientsex, primarysource.qualification) from openFDA count queries; serious-only PRR uses the drug serious report total and the term global serious total (N_serious=11,882,979); strata shown only when n ≥ 20
- Seriousness and sex counts from openFDA
count=serious,patient.patientsex,seriousnessdeath - ClinicalTrials.gov API v2 (query
BUSULFAN, results-bearing studies sorted by enrollment)
Page generated 2026-10-08. Label and PubChem text are retrieved automatically and may lag the current label; always check the current prescribing information. OpenPV is a beta research tool of the Open Source Medicine Foundation.