Active ingredient · pooled across combinations
Mebendazole: adverse event reports, pooled
4 ingredient sets in reports · 6 FDA-approved applications in the Green Book
Mebendazole appears, alone or combined with other ingredients, in 137 reports in FDA's animal adverse event database (January 1987 to April 2025). The figures here pool all 4 ingredient sets that include it.
The Green Book lists 6 FDA-approved applications containing it. openFDA masks brand and manufacturer names in adverse event records, so the reports counted here cannot be attributed to a particular brand.
1 reports arrived in the 12 months to March 2026, down 50% from 2 in the 12 months before. FDA posts reports quarterly with a delay of three to six months, so the newest months are incomplete and usually grow in later releases. That is about 3 reports a year over its reporting history and 0% of all reports.
Pooled across every set, the terms listed most often are abdominal pain (38.7%), diarrhoea (27.7%) and anorexia (21.2%). Many drugs combine several ingredients, and many reports list several drugs, so a term on this page may relate to any of them or to none.
Of reports that state seriousness, 23.1% were classed as serious (38.6% across the whole database); 16.1% record a death or euthanasia (6.4% overall). Ingredients used in older or sicker animals, or in anaesthesia and cancer care, carry higher shares for that reason alone.
Ingredient sets that include mebendazole
| Active ingredients recorded for the drug | Reports | Share of this page's reports | Latest 12 months |
|---|---|---|---|
| Mebendazole + Trichlorfon | 75 | 54.7% | 0 |
| Mebendazole | 50 | 36.5% | 0 |
| Mebendazole + Praziquantel + Pyrantel Pamoate | 8 | 5.8% | 1 |
| Ivermectin + Mebendazole + Pyrantel Pamoate | 4 | 2.9% | 0 |
Ordered by report count. FDA states that these data "cannot be used to estimate the risk associated with the product or compare one drug or device product with another"; counts follow sales volume and years on the market. A report can list more than one set, so shares can add to more than 100%.
Signs listed in reports, pooled
share of mebendazole reports listing the termall reports in the database
- Abdominal pain38.7%53
- Diarrhoea[diarrhea]27.7%38
- Anorexia[not eating]21.2%29
- Vomiting17.5%24
- Depression[dull, quiet or withdrawn]16.8%23
- Death15.3%21
- Elevated alanine aminotransferase (ALT)[a liver enzyme above the normal range]8.8%12
- Hypersalivation[drooling]8.8%12
- Icterus[jaundice (yellowing)]5.8%8
- Elevated serum alkaline phosphatase (SAP)[a liver and bone enzyme above the normal range]5.1%7
- PR-liver, lesion(s)[legacy FDA term: lesions found in the liver]5.1%7
- Behavioural disorder NOS[behaviour change, type not specified]3.6%5
- Elevated total bilirubin[bilirubin above the normal range]3.6%5
- Lack of efficacy (endoparasite) - hookworm[the product did not have the expected effect: hookworms]3.6%5
- Lack of efficacy (endoparasite) - whipworm[the product did not have the expected effect: whipworms]3.6%5
- Loose stool3.6%5
- Ataxia[unsteady, uncoordinated movement]2.9%4
- Elevated aspartate aminotransferase (AST)[a liver and muscle enzyme above the normal range]2.9%4
- Fever2.9%4
- Lethargy[unusually tired or inactive]2.9%4
- Pain NOS[NOS: not otherwise specified]2.9%4
- Unclassifiable adverse event[event that fits no dictionary term]2.9%4
- Weakness2.9%4
- Collapse2.2%3
- Convulsion[seizure]2.2%3
- Dyspnoea[difficulty breathing]2.2%3
- Hyperhidrosis2.2%3
- Recumbency[lying down and unable or unwilling to rise]2.2%3
- Abortion1.5%2
- Aggression1.5%2
Pooled across every ingredient set and every report that names the ingredient. One report can list several terms and several drugs; a term here may relate to any of them or to none.
Monthly reports by species, five years
By month of receipt; each panel has its own scale. The newest months are incomplete because FDA posts reports with a delay of three to six months.
Outcomes, report types and ages
Outcome recorded in the report
What kind of report it was
Age of the animal
Coloured bar: reports naming mebendazole. Grey bar: all 1,357,245 reports. Outcomes are as stated by the reporter; FDA has not necessarily determined whether any product played a part.
In context
| Measure | Mebendazole | All reports |
|---|---|---|
| Reports | 137 | 1,357,245 |
| Latest 12 months against the 12 before | -50% | -5% |
| Classed serious, of reports stating it | 23.1% | 38.6% |
| Death or euthanasia recorded, per 1,000 reports | 160.6 | 63.8 |
| Filed as lack of expected effectiveness (wholly or partly) | 6.6% | 23% |
Shares of reports, not of animals treated: how many animals receive the ingredient is not public. Ingredients used in anaesthesia, cancer care or in old animals carry more serious outcomes in their reports for that reason alone.
FDA-approved products containing mebendazole (Green Book)
Reference information, not report statistics. openFDA masks brand and manufacturer names in adverse event records, so the reports counted here cannot be attributed to a particular brand. The list below is the FDA Green Book as of 1 Oct 2026; nothing on this page says which of these products, if any, a report concerned.
| Trade name | Active ingredients | Sponsor | Approved for | Application |
|---|---|---|---|---|
| Telmin Equine Wormer | Mebendazole | Intervet, Inc. | Horses | NADA 091-736 |
| Telmin Syringe Formula | Mebendazole | Intervet, Inc. | Horses | NADA 097-221 |
| Telmin B Equine Wormer | Mebendazole, Trichlorfon | Intervet, Inc. | Horses | NADA 100-402 |
| Telmintic Powder | Mebendazole | Intervet, Inc. | Dogs | NADA 102-987 |
| Telmin | Mebendazole | Intervet, Inc. | Horses | NADA 118-394 |
| Telmin B Paste | Mebendazole, Trichlorfon | Intervet, Inc. | Horses | NADA 138-954 |
Species are the major species the Green Book search lists for the application ("—" where it lists another species or none). Approval dates are not part of the Green Book listing files and are not shown. Pioneer applications (NADA) come first, then generics (ANADA).
Questions about mebendazole reports
How many FDA adverse event reports mention mebendazole?
137 reports through March 2026, 1 of them in the latest 12 months, counting mebendazole alone and in combinations.
Which brands do these reports concern?
That cannot be known from the public data. openFDA masks brand and manufacturer names in adverse event records, so the reports counted here cannot be attributed to a particular brand. The Green Book reference list on this page names approved products containing mebendazole without any counts.
In which combinations is mebendazole reported?
Mebendazole + Trichlorfon (54.7% of these reports), Mebendazole (36.5% of these reports), Mebendazole + Praziquantel + Pyrantel Pamoate (5.8% of these reports) and Ivermectin + Mebendazole + Pyrantel Pamoate (2.9% of these reports).
What reactions are reported for mebendazole?
abdominal pain (38.7%), diarrhoea (27.7%), anorexia (21.2%), vomiting (17.5%) and depression (16.8%). Shares are of reports naming the ingredient; one report can list several terms.
Which animals are these reports about?
horse (54.7%), dog (41.6%) and human exposure (2.2%).
Does a high count mean mebendazole is a problem ingredient?
A count cannot show that. FDA states that "there is no certainty that the reported drug or device caused the adverse event" and that the event "may have been related to an underlying disease, other drugs used at the same time or other non-drug related sources." Widely used ingredients collect more reports because more animals receive them.
How do I report a problem?
Call the drug company using the number on the label, or send Form FDA 1932a to FDA. See the guide on how to report.
Where this comes from. Counts are built from the openFDA Animal & Veterinary adverse event bulk files released 28 Sep 2026, which hold reports FDA's Center for Veterinary Medicine received through 31 Mar 2026. openFDA masks brand and manufacturer names in these files, so drugs are counted by the active ingredients each record discloses and no figure is attributed to a brand, application or company. Ingredient names, and the separate reference lists of approved products, follow the FDA Green Book as of 1 Oct 2026. Ingredient names follow the Green Book; salts and forms are kept as FDA lists them. Drug entries are matched by the active ingredients their unmasked ingredient field discloses. No report text, lot numbers or reporter details are published. See the methodology and sources; FDA's record is authoritative, and corrections are handled within five working days.