Busulfan: adverse event reports filed with FDA

11,825

reports as suspect product

0.1% of all reports · about 526 a year

1,095

reports, 12 months to June 2026

1,045 in the 12 months before

94.9%

marked serious by the reporter

93.5% across the class

28.9%

record death among outcomes, as reported

3,412 reports · not verified by FDA

Reports by month, five years

Reports by the month FDA received them. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.

By year received

2026 covers reports received through June 2026 only.

Reactions recorded in the reports

share of Busulfan reports recording the termmedian drug in alkylating drug

1. Product use in unapproved indicationused for a purpose not on the label12.1%1,428
2. Off label useused for a purpose or in a way not on the label11.7%1,386
3. Mucosal inflammation8%941
4. Venoocclusive liver disease6.8%804
5. Cytomegalovirus infection5.7%673
6. Febrile neutropeniafever with low white blood cells5.6%663
7. Graft versus host disease5.5%655
8. Drug ineffectivethe medicine did not work as expected5.2%610
9. Pyrexiafever4.9%577
10. Cytomegalovirus infection reactivation4.4%524
11. Acute graft versus host disease3.9%463
12. Infectionan infection, type not specified3.6%429
13. Thrombocytopenialow platelets3.6%428
14. Sepsisa severe body-wide response to infection3.6%421
15. Chronic graft versus host disease3.4%400
16. Respiratory failurethe lungs could not supply enough oxygen3.2%384
17. Diarrhoealoose or frequent stools3.2%379
18. Pneumonialung infection3.2%376
19. Acute graft versus host disease in skin3.2%374
20. Venoocclusive disease3.1%366
21. Cystitis haemorrhagic3.1%362
22. Pancytopenialow counts of all blood cells3%351
23. Neutropenialow neutrophils, a type of white blood cell2.8%335
24. BK virus infection2.6%313
25. Thrombotic microangiopathy2.4%283
26. Multiple organ dysfunction syndromeseveral organs failing2.3%275
27. Epstein-Barr virus infection2.2%258
28. Aplastic anaemia2.1%247
29. Acute kidney injurysudden loss of kidney function2%240
30. Septic shockshock arising from infection2%238

Top 30 of 1,407 MedDRA preferred terms recorded across these reports, with a plain-language gloss where one is available. One report can record several terms. The hollow bar is the median share across the 23 drugs in the alkylating drug class; it describes the reports, not the patients. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Outcomes recorded

Outcome flags as the reporter set them; a report can carry several, and "other serious" is FDA's own category for serious reports outside the named outcomes. Grey bar: all 253,205 reports in the class. FDA has not verified any outcome and states that the reports "cannot be used to estimate the incidence of these events."

Patients and reporters

Age and sex as stated in the report; the reporter's qualification is the primary source recorded by FDA. 24.9% of reports give the United States as the country of the event or reporter.

Reason for use recorded

The indication field is filled in by the reporter and is often blank; shares are of all 11,825 reports.

Drugs most often listed in the same reports

Other products listed in reports where Busulfan is a suspect product, whatever their own role. Co-listing means the two were recorded together; it says nothing about either product's part in the event. Only the 2,500 most-reported names are counted here.

In context

Shares are of reports, not of patients treated. The number of people taking a product is not in the data, so none of these figures is a rate, and differences between columns reflect who takes a product, who reports and how long it has been sold. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Other drugs in the alkylating drug class

Ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic." A brand and its generic are separate rows because reporters name them separately.

Where this comes from. Counts are built from the openFDA Drug Adverse Event (FAERS) bulk export released 28 Sep 2026, which holds reports FDA received through 30 Jun 2026. Drug names are as reported, resolved to the brand or generic name on the FDA label where openFDA's harmonisation matched them; classes are the pharmacologic class (EPC) from the label and the National Drug Code Directory of 17 Sep 2026. A report counts here when it lists Busulfan as a suspect or interacting product; reports listing it only as a concomitant medication (3,866) are excluded. No report narrative, lot number, patient detail or reporter identity is published. See the methodology and sources; FDA's record is authoritative, and corrections are handled within five working days.