Reported Reactions

Drugs › Antimetabolite

Brand name · Hydroxyurea

Hydrea: adverse event reports filed with FDA

2,669 reports list it as a suspect or interacting product, 2004–2026. Class: Antimetabolite. Also reported as Hydrea Caps.

2,669
reports as suspect product
0% of all reports · about 119 a year
38
reports, 12 months to June 2026
49 in the 12 months before
88%
marked serious by the reporter
89.5% across the class
12.6%
record death among outcomes, as reported
336 reports · not verified by FDA

2,669 adverse event reports received by FDA list the brand name Hydrea (hydroxyurea) as a suspect or interacting product, from January 2004 to June 2026. A further 3,520 reports list it only as a concomitant medication, and those are not counted in the figures on this page.

In the 12 months to June 2026, 38 reports listed it, down 22% from 49 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 119 reports a year and 0% of the 20,646,523 reports in the database, and 30.5% of the reports for the antimetabolite class. How many people take it is not in the data, so a count is not a rate of occurrence.

The reactions recorded most often are off label use (6.3%), pyrexia (5.1%) and anaemia (5%). A report can list several reactions, so shares add to more than 100%; 573 different terms appear across these reports. Off label use is recorded in 6.3% of these reports, about the same share as in the median antimetabolite drug (6.3%).

88% of the reports are marked serious by the reporter (89.5% across the class); 12.6% record death among the outcomes and 43.9% record hospitalisation, as reported. 34.7% of the reports came from physicians, and the largest patient age group is 75 and over (26.4%). 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

01122Jul 2021: 15Aug 2021: 12Sep 2021: 9Oct 2021: 22Nov 2021: 17Dec 2021: 152022Jan 2022: 8Feb 2022: 11Mar 2022: 17Apr 2022: 16May 2022: 5Jun 2022: 15Jul 2022: 22Aug 2022: 18Sep 2022: 19Oct 2022: 17Nov 2022: 6Dec 2022: 62023Jan 2023: 5Feb 2023: 6Mar 2023: 7Apr 2023: 2May 2023: 2Jun 2023: 2Jul 2023: 2Aug 2023: 3Sep 2023: 8Oct 2023: 6Nov 2023: 1Dec 2023: 22024Jan 2024: 7Feb 2024: 7Mar 2024: 1Apr 2024: 3May 2024: 2Jun 2024: 5Jul 2024: 4Aug 2024: 7Sep 2024: 0Oct 2024: 0Nov 2024: 7Dec 2024: 22025Jan 2025: 2Feb 2025: 7Mar 2025: 1Apr 2025: 15May 2025: 2Jun 2025: 2Jul 2025: 6Aug 2025: 1Sep 2025: 4Oct 2025: 3Nov 2025: 0Dec 2025: 92026Jan 2026: 2Feb 2026: 0Mar 2026: 0Apr 2026: 6May 2026: 5Jun 2026: 2

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

01322632004: 3820042005: 612006: 672007: 7020072008: 682009: 692010: 7820102011: 832012: 902013: 7320132014: 1302015: 1632016: 20420162017: 1902018: 2632019: 24420192020: 2412021: 2172022: 16020222023: 462024: 452025: 5220252026: 15

2026 covers reports received through June 2026 only.

Reactions recorded in the reports

share of Hydrea reports recording the termmedian drug in antimetabolite

  1. Off label useused for a purpose or in a way not on the label6.3%168
  2. Pyrexiafever5.1%136
  3. Anaemialow red blood cells5%133
  4. Skin ulceran open sore on the skin3.2%85
  5. Platelet count decreasedlow platelet count3.1%84
  6. Thrombocytopenialow platelets3%79
  7. Fatiguetiredness2.9%78
  8. Nauseafeeling sick2.8%74
  9. Diarrhoealoose or frequent stools2.6%70
  10. Drug ineffectivethe medicine did not work as expected2.4%65
  11. Dyspnoeashortness of breath2.4%63
  12. Pancytopenialow counts of all blood cells2.2%60
  13. Intentional product use issuedeliberate use not as intended2.2%59
  14. Haemoglobin decreasedlow haemoglobin2.1%55
  15. Interstitial lung diseasescarring or inflammation of lung tissue2%54
  16. White blood cell count decreasedlow white cell count2%53
  17. Deaththe patient died; cause not stated by this term1.9%52
  18. Dysphagiadifficulty swallowing1.9%52
  19. Pneumonialung infection1.9%52
  20. Astheniaweakness or lack of energy1.9%50
  21. Falla fall1.8%49
  22. Vomitingbeing sick1.8%48
  23. Headachehead pain1.6%44
  24. Painpain, site not specified1.6%42
  25. Dizzinesslight-headedness or unsteadiness1.5%40
  26. Pain in extremitypain in an arm or leg1.4%38
  27. Pleural effusionfluid around the lung1.4%37

Top 30 of 573 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 3 drugs in the antimetabolite 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

Death12.6%336
Life-threatening5.8%155
Hospitalisation (initial or prolonged)43.9%1,172
Disability2.2%59
Congenital anomaly0.4%10
Other serious61.3%1,636
Not serious12%319

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 8,764 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 20.3%9
2 to 110.5%14
12 to 171%27
18 to 445.4%143
45 to 6414.5%386
65 to 7419.1%510
75 and over26.4%704
Age not given32.8%876

Patient sex

Female44.1%1,178
Male38.8%1,035
Not given17.1%456

Who reported

Physician34.7%926
Pharmacist18.5%495
Other health professional16.8%448
Lawyer0%1
Consumer or non-health professional28.8%770
Not given1.1%29

Age and sex as stated in the report; the reporter's qualification is the primary source recorded by FDA. 24.1% of reports give the United States as the country of the event or reporter.

Reason for use recorded

Indication as recorded (MedDRA)ReportsShare
Essential thrombocythaemia40015%
Polycythaemia vera29911.2%
Chronic myeloid leukaemia1656.2%
Thrombocytosis1104.1%
Acute myeloid leukaemia963.6%
Polycythaemia652.4%

The indication field is filled in by the reporter and is often blank; shares are of all 2,669 reports.

Drugs most often listed in the same reports

Drug (any role in the report)ReportsShare of Hydrea reports
Kardegic1816.8%
Allopurinol1626.1%
Jakafi1565.8%
Aspirin1425.3%
Jakavi973.6%
Furosemide813%
Cytarabine642.4%
Eliquis471.8%
Gleevec461.7%
Folic acid431.6%

Other products listed in reports where Hydrea 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

MeasureHydreaAntimetaboliteAll reports
Reports as suspect product2,6698,76420,646,523
Share of that pool—30.5%0%
Reports, latest 12 months38—1,332,454
Marked serious88%89.5%57.4%
Death recorded among outcomes, per 1,000 reports12613991
Hospitalisation recorded, per 1,000 reports439394213
Consumer-filed share28.8%20.3%45.8%
Top term, share of reportsOff label use 6.3%median 6.3%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 antimetabolite class

DrugName typeReportsLatest 12 monthsMarked serious
Hydroxyureageneric4,26032686.8%
Thioguaninegeneric1,8356797.9%

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 Hydrea reports

How many adverse event reports has FDA received for Hydrea?

2,669 reports list Hydrea as a suspect or interacting product in the openFDA FAERS release of 28 Sep 2026, covering reports received through June 2026. 38 of them arrived in the latest 12 months. Another 3,520 list it only as a concomitant medication.

What reactions are recorded in Hydrea reports?

off label use (6.3%), pyrexia (5.1%), anaemia (5%), skin ulcer (3.2%) and platelet count decreased (3.1%). 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 Hydrea was responsible.

How serious are the reports?

88% are marked serious by the reporter. Among the outcomes recorded, 12.6% of reports include death and 43.9% 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?

physician (34.7%), consumer or non-health professional (28.8%) and pharmacist (18.5%). Most reports reach FDA through the manufacturer, which must forward reports it receives.

Are reports for Hydrea rising?

38 reports in the 12 months to June 2026, down 22% from 49 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 Hydrea 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 Hydrea?

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 Hydrea as a suspect or interacting product; reports listing it only as a concomitant medication (3,520) 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.