Reported Reactions

Drugs › Nucleoside metabolic inhibitor

Brand name · Azacitidine

Onureg: adverse event reports filed with FDA

755 reports list it as a suspect or interacting product, 2020–2026. Class: Nucleoside metabolic inhibitor.

755
reports as suspect product
0% of all reports · about 131 a year
69
reports, 12 months to June 2026
147 in the 12 months before
49.8%
marked serious by the reporter
92.2% across the class
13.8%
record death among outcomes, as reported
104 reports · not verified by FDA

Between October 2020 and June 2026, 755 adverse event reports received by FDA list the brand name Onureg (azacitidine) as a suspect or interacting product. Reports that mention it only as a concomitant medication (37) are left out of every figure here.

In the 12 months to June 2026, 69 reports listed it, down 53% from 147 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. Over its reporting history that is about 131 reports a year and 0% of the 20,646,523 reports in the database, and 0.2% of the reports for the nucleoside metabolic inhibitor class. How many people take it is not in the data, so a count is not a rate of occurrence.

The MedDRA terms listed most often are off label use (16.6%), nausea (15.5%) and death (11.4%). A report can list several reactions, so shares add to more than 100%; 101 different terms appear across these reports. Off label use is recorded in 16.6% of these reports, a larger share than in the median nucleoside metabolic inhibitor drug (6.1%).

49.8% of the reports are marked serious by the reporter (92.2% across the class); 13.8% record death among the outcomes and 19.6% record hospitalisation, as reported. 55.5% of the reports came from consumers, and the largest patient age group is 65 to 74 (28.6%). FDA states that "a causal relationship cannot be established between product and reactions listed in a report" and that for any given report "there is no certainty that a suspected drug caused the event."

Reports by month, five years

01632Jul 2021: 12Aug 2021: 6Sep 2021: 16Oct 2021: 6Nov 2021: 12Dec 2021: 162022Jan 2022: 15Feb 2022: 9Mar 2022: 17Apr 2022: 11May 2022: 28Jun 2022: 10Jul 2022: 12Aug 2022: 17Sep 2022: 23Oct 2022: 15Nov 2022: 32Dec 2022: 92023Jan 2023: 10Feb 2023: 17Mar 2023: 18Apr 2023: 10May 2023: 10Jun 2023: 16Jul 2023: 12Aug 2023: 10Sep 2023: 8Oct 2023: 10Nov 2023: 18Dec 2023: 92024Jan 2024: 10Feb 2024: 14Mar 2024: 9Apr 2024: 10May 2024: 12Jun 2024: 13Jul 2024: 20Aug 2024: 20Sep 2024: 17Oct 2024: 11Nov 2024: 11Dec 2024: 142025Jan 2025: 11Feb 2025: 9Mar 2025: 8Apr 2025: 9May 2025: 8Jun 2025: 9Jul 2025: 4Aug 2025: 5Sep 2025: 3Oct 2025: 6Nov 2025: 3Dec 2025: 82026Jan 2026: 8Feb 2026: 5Mar 2026: 6Apr 2026: 5May 2026: 6Jun 2026: 10

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

0991982020: 620202021: 11920212022: 19820222023: 14820232024: 16120242025: 8320252026: 402026

2026 covers reports received through June 2026 only.

Reactions recorded in the reports

share of Onureg reports recording the termmedian drug in nucleoside metabolic inhibitor

  1. Off label useused for a purpose or in a way not on the label16.6%125
  2. Nauseafeeling sick15.5%117
  3. Deaththe patient died; cause not stated by this term11.4%86
  4. Vomitingbeing sick10.1%76
  5. Diarrhoealoose or frequent stools7.8%59
  6. Fatiguetiredness4%30
  7. Constipationconstipation3.8%29
  8. Hospitalisationadmission to hospital3.8%29
  9. White blood cell count decreasedlow white cell count3.7%28
  10. Neutropenialow neutrophils, a type of white blood cell2.8%21
  11. Illness2.6%20
  12. Astheniaweakness or lack of energy2.5%19
  13. Adverse eventan unwanted medical event, type not specified2.3%17
  14. Platelet count decreasedlow platelet count2.3%17
  15. Acute myeloid leukaemia recurrent2.1%16
  16. Covid-19COVID-19 infection2.1%16
  17. Painpain, site not specified1.6%12
  18. Thrombocytopenialow platelets1.6%12
  19. Drug ineffectivethe medicine did not work as expected1.5%11
  20. Decreased appetitereduced appetite1.3%10
  21. Pneumonialung infection1.3%10
  22. Abdominal pain upperupper stomach pain1.1%8
  23. Pancytopenialow counts of all blood cells1.1%8
  24. Pyrexiafever1.1%8
  25. Abdominal discomfortstomach discomfort0.9%7

Top 30 of 101 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 19 drugs in the nucleoside metabolic inhibitor 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

Death13.8%104
Life-threatening0.9%7
Hospitalisation (initial or prolonged)19.6%148
Disability0.3%2
Congenital anomaly0%0
Other serious30.7%232
Not serious50.2%379

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 313,386 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

Patient age

Under 20%0
2 to 110%0
12 to 170.5%4
18 to 448.5%64
45 to 6420.9%158
65 to 7428.6%216
75 and over21.5%162
Age not given20%151

Patient sex

Female43.8%331
Male50.3%380
Not given5.8%44

Who reported

Physician17.2%130
Pharmacist8.7%66
Other health professional15.9%120
Lawyer0%0
Consumer or non-health professional55.5%419
Not given2.6%20

Age and sex as stated in the report; the reporter's qualification is the primary source recorded by FDA. 87.4% of reports give the United States as the country of the event or reporter.

Reason for use recorded

Indication as recorded (MedDRA)ReportsShare
Acute myeloid leukaemia32042.4%
Myelodysplastic syndrome182.4%
Myeloid leukaemia111.5%
Acute monocytic leukaemia70.9%
Acute myeloid leukaemia (in remission)60.8%
Peripheral t-cell lymphoma unspecified60.8%

The indication field is filled in by the reporter and is often blank; shares are of all 755 reports.

Drugs most often listed in the same reports

Drug (any role in the report)ReportsShare of Onureg reports
Venclexta364.8%
Ondansetron354.6%
Acyclovir344.5%
Ergocalciferol162.1%
Venetoclax162.1%
Zofran131.7%
Allopurinol111.5%
Eliquis111.5%
Levofloxacin91.2%
Pantoprazole91.2%

Other products listed in reports where Onureg 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

MeasureOnuregNucleoside metabolic inhibitorAll reports
Reports as suspect product755313,38620,646,523
Share of that pool—0.2%0%
Reports, latest 12 months69—1,332,454
Marked serious49.8%92.2%57.4%
Death recorded among outcomes, per 1,000 reports13821091
Hospitalisation recorded, per 1,000 reports196380213
Consumer-filed share55.5%11.4%45.8%
Top term, share of reportsOff label use 16.6%median 6.1%4.1%

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 nucleoside metabolic inhibitor class

DrugName typeReportsLatest 12 monthsMarked serious
Fluorouracilgeneric60,4515,31596.1%
Capecitabinegeneric51,7833,28183.3%
Cytarabinegeneric50,7413,54597.9%
Gemcitabinegeneric33,1982,92097.9%
Xelodabrand32,27928073%
Fludarabinebrand20,2601,90098.7%
Azacitidinegeneric14,9691,83098%
Gemcitabine hydrochloridegeneric12,3991,16497.1%
Mercaptopurinegeneric10,54050795.8%
Vidazabrand9,08735896.9%
Fludarabine phosphategeneric8,42641998.5%
Decitabinegeneric3,02625896.8%
Clofarabinegeneric2,0207796.5%
Purixangeneric7672981.5%
Pentostatingeneric6971691.7%

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.

Questions about Onureg reports

How many adverse event reports has FDA received for Onureg?

755 reports list Onureg as a suspect or interacting product in the openFDA FAERS release of 28 Sep 2026, covering reports received through June 2026. 69 of them arrived in the latest 12 months. Another 37 list it only as a concomitant medication.

What reactions are recorded in Onureg reports?

off label use (16.6%), nausea (15.5%), death (11.4%), vomiting (10.1%) and diarrhoea (7.8%). These are MedDRA preferred terms coded from what the reporter described; a report can list several, and a term's presence is not a finding that Onureg was responsible.

How serious are the reports?

49.8% are marked serious by the reporter. Among the outcomes recorded, 13.8% of reports include death and 19.6% include hospitalisation. FDA has not verified these outcomes and states that the reports "cannot be used to estimate the incidence" of the events.

Who files these reports?

consumer or non-health professional (55.5%), physician (17.2%) and other health professional (15.9%). Most reports reach FDA through the manufacturer, which must forward reports it receives.

Are reports for Onureg rising?

69 reports in the 12 months to June 2026, down 53% from 147 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. Counts also move with how many people take a product, its time on the market and publicity.

Do these reports show that Onureg was responsible for these reactions?

No. FDA states that "a causal relationship cannot be established between product and reactions listed in a report" and that for any given report "there is no certainty that a suspected drug caused the event." The reaction may relate to the condition being treated, to other medicines, or to something else.

Is this a list of the side effects of Onureg?

No. It is a count of what was reported to FDA. The adverse reactions observed in clinical studies are printed on the FDA-approved label, which a pharmacist or clinician can go through with you.

How do I report an adverse event?

Consumers and health professionals can report to FDA through MedWatch (Form FDA 3500 online, or 1-800-FDA-1088), or to the manufacturer, which must pass reports on. See the guide on how to report.

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 Onureg as a suspect or interacting product; reports listing it only as a concomitant medication (37) 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.

Drug data (FAERS) through 30 Jun 2026; device data (MAUDE) through 31 Aug 2026. Not medical advice.