Generic name
Cladribine: adverse event reports filed with FDA
2,083 reports list it as a suspect or interacting product, 2004–2026. Class: Purine antimetabolite.
- 2,083
- reports as suspect product
- 0% of all reports · about 93 a year
- 200
- reports, 12 months to June 2026
- 241 in the 12 months before
- 96.2%
- marked serious by the reporter
- 90.3% across the class
- 19.8%
- record death among outcomes, as reported
- 413 reports · not verified by FDA
2,083 adverse event reports received by FDA list cladribine, a generic name as a suspect or interacting product, from March 2004 to June 2026. A further 642 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, 200 reports listed it, down 17% from 241 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 93 reports a year and 0% of the 20,646,523 reports in the database, and 4.2% of the reports for the purine antimetabolite 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 (9.8%), febrile neutropenia (8.4%) and pyrexia (7.1%). A report can list several reactions, so shares add to more than 100%; 569 different terms appear across these reports. Off label use is recorded in 9.8% of these reports, a smaller share than in the median purine antimetabolite drug (12.4%).
96.2% of the reports are marked serious by the reporter (90.3% across the class); 19.8% record death among the outcomes and 28.5% record hospitalisation, as reported. 51% of the reports came from other health professionals, and the largest patient age group is 45 to 64 (24%). 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
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 Cladribine reports recording the termmedian drug in purine antimetabolite
- Off label useused for a purpose or in a way not on the label9.8%204
- Febrile neutropeniafever with low white blood cells8.4%175
- Pyrexiafever7.1%147
- Drug ineffectivethe medicine did not work as expected6.9%144
- Neutropenialow neutrophils, a type of white blood cell5.8%121
- Pancytopenialow counts of all blood cells5.5%115
- Thrombocytopenialow platelets4.3%90
- Product use in unapproved indicationused for a purpose not on the label4.1%85
- Lymphopenia3.7%77
- Pneumonialung infection3.6%74
- Rash maculo-papulara rash of flat and raised spots3.4%70
- Infectionan infection, type not specified3.2%66
- Sepsisa severe body-wide response to infection3%63
- Multiple sclerosis relapsea flare of multiple sclerosis2.9%61
- Disease progressionthe disease advanced2.7%56
- Nauseafeeling sick2.6%54
- Myelosuppression2.5%53
- Septic shockshock arising from infection2.5%53
- Leukopenialow white blood cells2.4%51
- Anaemialow red blood cells2.2%46
- Diarrhoealoose or frequent stools2.1%44
- Deaththe patient died; cause not stated by this term2.1%43
- Fatiguetiredness1.9%40
- Vomitingbeing sick1.9%39
- Multiple organ dysfunction syndromeseveral organs failing1.8%38
- Covid-19COVID-19 infection1.7%36
- Rashskin rash1.7%36
- Respiratory failurethe lungs could not supply enough oxygen1.7%36
- Haematotoxicity1.7%35
Top 30 of 569 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 5 drugs in the purine 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
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 49,725 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
Patient sex
Who reported
Age and sex as stated in the report; the reporter's qualification is the primary source recorded by FDA. 33.9% of reports give the United States as the country of the event or reporter.
Reason for use recorded
| Indication as recorded (MedDRA) | Reports | Share |
|---|---|---|
| Hairy cell leukaemia | 372 | 17.9% |
| Acute myeloid leukaemia | 324 | 15.6% |
| Multiple sclerosis | 160 | 7.7% |
| Chronic lymphocytic leukaemia | 124 | 6% |
| Langerhans' cell histiocytosis | 112 | 5.4% |
| Relapsing-remitting multiple sclerosis | 85 | 4.1% |
The indication field is filled in by the reporter and is often blank; shares are of all 2,083 reports.
Drugs most often listed in the same reports
| Drug (any role in the report) | Reports | Share of Cladribine reports |
|---|---|---|
| Cytarabine | 652 | 31.3% |
| Rituximab | 314 | 15.1% |
| Cyclophosphamide | 309 | 14.8% |
| Mitoxantrone | 219 | 10.5% |
| Filgrastim | 159 | 7.6% |
| Etoposide | 156 | 7.5% |
| Methotrexate | 140 | 6.7% |
| Idarubicin | 132 | 6.3% |
| Prednisone | 121 | 5.8% |
| Venetoclax | 102 | 4.9% |
Other products listed in reports where Cladribine 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
| Measure | Cladribine | Purine antimetabolite | All reports |
|---|---|---|---|
| Reports as suspect product | 2,083 | 49,725 | 20,646,523 |
| Share of that pool | — | 4.2% | 0% |
| Reports, latest 12 months | 200 | — | 1,332,454 |
| Marked serious | 96.2% | 90.3% | 57.4% |
| Death recorded among outcomes, per 1,000 reports | 198 | 142 | 91 |
| Hospitalisation recorded, per 1,000 reports | 285 | 319 | 213 |
| Consumer-filed share | 3.6% | 18.3% | 45.8% |
| Top term, share of reports | Off label use 9.8% | median 12.4% | 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 purine antimetabolite class
| Drug | Name type | Reports | Latest 12 months | Marked serious |
|---|---|---|---|---|
| Azathioprine | generic | 33,639 | 2,890 | 94.7% |
| Mavenclad | brand | 6,763 | 1,128 | 67.2% |
| Imuran | brand | 5,749 | 407 | 87.3% |
| Azathioprine sodium | generic | 1,491 | 166 | 99.3% |
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 Cladribine reports
How many adverse event reports has FDA received for Cladribine?
2,083 reports list Cladribine as a suspect or interacting product in the openFDA FAERS release of 28 Sep 2026, covering reports received through June 2026. 200 of them arrived in the latest 12 months. Another 642 list it only as a concomitant medication.
What reactions are recorded in Cladribine reports?
off label use (9.8%), febrile neutropenia (8.4%), pyrexia (7.1%), drug ineffective (6.9%) and neutropenia (5.8%). 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 Cladribine was responsible.
How serious are the reports?
96.2% are marked serious by the reporter. Among the outcomes recorded, 19.8% of reports include death and 28.5% 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?
other health professional (51%), physician (40.8%) and consumer or non-health professional (3.6%). Most reports reach FDA through the manufacturer, which must forward reports it receives.
Are reports for Cladribine rising?
200 reports in the 12 months to June 2026, down 17% from 241 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 Cladribine 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 Cladribine?
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 Cladribine as a suspect or interacting product; reports listing it only as a concomitant medication (642) 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.