Drugs › Histamine-1 receptor inhibitor
Generic name
Ketotifen fumarate: adverse event reports filed with FDA
290 reports list it as a suspect or interacting product, 2004–2026. Class: Histamine-1 receptor inhibitor.
- 290
- reports as suspect product
- 0% of all reports · about 13 a year
- 10
- reports, 12 months to June 2026
- 10 in the 12 months before
- 22.8%
- marked serious by the reporter
- 3.1% across the class
- 0.3%
- record death among outcomes, as reported
- 1 reports · not verified by FDA
290 adverse event reports received by FDA list ketotifen fumarate, a generic name as a suspect or interacting product, from November 2004 to May 2026. A further 811 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, 10 reports listed it, close to the 10 of 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 13 reports a year and 0% of the 20,646,523 reports in the database, and 4.1% of the reports for the histamine-1 receptor inhibitor class. How many people take it is not in the data, so a count is not a rate of occurrence.
Reporters most often recorded treatment failure (48.6%), drug ineffective (18.3%) and hypersensitivity (2.8%). A report can list several reactions, so shares add to more than 100%; 54 different terms appear across these reports. Treatment failure is recorded in 48.6% of these reports, a smaller share than in the median histamine-1 receptor inhibitor drug (73.6%).
22.8% of the reports are marked serious by the reporter (3.1% across the class); 0.3% record death among the outcomes and 7.9% record hospitalisation, as reported. 72.1% of the reports came from consumers, and the largest patient age group is 18 to 44 (6.6%). 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
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 Ketotifen fumarate reports recording the termmedian drug in histamine-1 receptor inhibitor
- Treatment failurethe treatment did not work48.6%141
- Drug ineffectivethe medicine did not work as expected18.3%53
- Hypersensitivityan allergic-type reaction2.8%8
- Condition aggravatedthe condition being treated got worse1.4%4
- Dyspnoeashortness of breath1.4%4
- Abdominal painstomach or belly pain1%3
- Product use in unapproved indicationused for a purpose not on the label1%3
- Rashskin rash1%3
- Somnolencedrowsiness1%3
- Amnesiamemory loss0.7%2
- Conjunctivitispink eye0.7%2
- Dacryostenosis acquired0.7%2
- Decreased appetitereduced appetite0.7%2
- Dermatitis bullous0.7%2
- Dizzinesslight-headedness or unsteadiness0.7%2
- Drug interactionan interaction between medicines0.7%2
- Eye allergy0.7%2
- Eye swellinga swollen eye0.7%2
- Inflammationinflammation0.7%2
- Lethargysluggishness0.7%2
- Leukopenialow white blood cells0.7%2
- Mucosal ulceration0.7%2
- Muscular weaknessmuscle weakness0.7%2
- Ocular toxicity0.7%2
- Off label useused for a purpose or in a way not on the label0.7%2
- Pruritusitching0.7%2
Top 30 of 54 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 histamine-1 receptor 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
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 7,029 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. 80% of reports give the United States as the country of the event or reporter.
Reason for use recorded
| Indication as recorded (MedDRA) | Reports | Share |
|---|---|---|
| Mast cell activation syndrome | 2 | 0.7% |
| Nasopharyngitis | 2 | 0.7% |
The indication field is filled in by the reporter and is often blank; shares are of all 290 reports.
Drugs most often listed in the same reports
| Drug (any role in the report) | Reports | Share of Ketotifen fumarate reports |
|---|---|---|
| Zaditor | 91 | 31.4% |
| Pataday | 90 | 31% |
| Patanol | 68 | 23.4% |
| Olopatadine hydrochloride | 60 | 20.7% |
| Azelastine | 41 | 14.1% |
| Azelastine hydrochloride | 40 | 13.8% |
| Ketorolac | 19 | 6.6% |
| Montelukast sodium | 6 | 2.1% |
| Ranitidine | 6 | 2.1% |
Other products listed in reports where Ketotifen fumarate 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 | Ketotifen fumarate | Histamine-1 receptor inhibitor | All reports |
|---|---|---|---|
| Reports as suspect product | 290 | 7,029 | 20,646,523 |
| Share of that pool | — | 4.1% | 0% |
| Reports, latest 12 months | 10 | — | 1,332,454 |
| Marked serious | 22.8% | 3.1% | 57.4% |
| Death recorded among outcomes, per 1,000 reports | 3 | 5 | 91 |
| Hospitalisation recorded, per 1,000 reports | 79 | 11 | 213 |
| Consumer-filed share | 72.1% | 83.3% | 45.8% |
| Top term, share of reports | Treatment failure 48.6% | median 73.6% | 0.4% |
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 histamine-1 receptor inhibitor class
| Drug | Name type | Reports | Latest 12 months | Marked serious |
|---|---|---|---|---|
| Zaditor | brand | 3,290 | 3 | 1.6% |
| Olopatadine hydrochloride | generic | 2,404 | 61 | 6.1% |
| Alaway | brand | 1,335 | 36 | 1.7% |
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 Ketotifen fumarate reports
How many adverse event reports has FDA received for Ketotifen fumarate?
290 reports list Ketotifen fumarate as a suspect or interacting product in the openFDA FAERS release of 28 Sep 2026, covering reports received through June 2026. 10 of them arrived in the latest 12 months. Another 811 list it only as a concomitant medication.
What reactions are recorded in Ketotifen fumarate reports?
treatment failure (48.6%), drug ineffective (18.3%), hypersensitivity (2.8%), contraindicated product administered (1.7%) and condition aggravated (1.4%). 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 Ketotifen fumarate was responsible.
How serious are the reports?
22.8% are marked serious by the reporter. Among the outcomes recorded, 0.3% of reports include death and 7.9% 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?
consumer or non-health professional (72.1%), physician (10.7%) and other health professional (9.7%). Most reports reach FDA through the manufacturer, which must forward reports it receives.
Are reports for Ketotifen fumarate rising?
10 reports in the 12 months to June 2026, close to the 10 of 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 Ketotifen fumarate 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 Ketotifen fumarate?
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 Ketotifen fumarate as a suspect or interacting product; reports listing it only as a concomitant medication (811) 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.