Active ingredient · pooled across combinations

Trichlorfon: adverse event reports, pooled

4 ingredient sets in reports · 13 FDA-approved applications in the Green Book

Read this first · FDA's caveat, in its words

An API dataset query result cannot be used to estimate the risk associated with the product or compare one drug or device product with another. When looking at the results, be aware that there is no certainty that the reported drug or device caused the adverse event. This dataset should not be the sole source of information for clinical decision-making or other assumptions about the safety or effectiveness of a product. The adverse event may have been related to an underlying disease, other drugs used at the same time or other non-drug related sources. FDA Center for Veterinary Medicine

Do not rely on openFDA to make decisions regarding medical care. While we make every effort to ensure that data is accurate, you should assume all results are unvalidated. We may limit or otherwise restrict your access to the API in line with our Terms of Service.

Not veterinary advice. This site lists what was reported to FDA. For an animal that is unwell, contact a veterinarian.

137reports naming the ingredient, 1987–19950% of all reports · about 3 a year

0reports, 12 months to March 20260 in the 12 months before

0%classed serious, as reportedall reports: 38.6%

96.4%of reports concern horsesdog 3.6%

Trichlorfon appears, alone or combined with other ingredients, in 137 reports in FDA's animal adverse event database (January 1987 to October 1995). The figures here pool all 4 ingredient sets that include it.

The Green Book lists 13 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.

0 reports arrived in the 12 months to March 2026, and none 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 (56.2%), diarrhoea (37.2%) and death (17.5%). 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, 0% were classed as serious (38.6% across the whole database); 20.4% 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 trichlorfon

Active ingredients recorded for the drug	Reports	Share of this page's reports
Mebendazole + Trichlorfon	75	54.7%
Febantel + Trichlorfon	29	21.2%
Phenothiazine + Piperazine + Trichlorfon	18	13.1%
Oxfendazole + Trichlorfon	15	10.9%

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 trichlorfon reports listing the termall reports in the database

Abdominal pain56.2%77
Diarrhoea[diarrhea]37.2%51
Death17.5%24
Hypersalivation[drooling]17.5%24
Anorexia[not eating]16.8%23
Depression[dull, quiet or withdrawn]12.4%17
Pain NOS[NOS: not otherwise specified]8.8%12
Ataxia[unsteady, uncoordinated movement]5.8%8
Hyperhidrosis5.8%8
Buccal irritation4.4%6
Lip oedema4.4%6
Abortion3.6%5
Behavioural disorder NOS[behaviour change, type not specified]3.6%5
Recumbency[lying down and unable or unwilling to rise]3.6%5
Tongue oedema3.6%5
Death by euthanasia[the animal was euthanized]2.9%4
Dyspnoea[difficulty breathing]2.9%4
Loose stool2.9%4
Organophosphate toxicity NOS[NOS: not otherwise specified]2.9%4
Urticaria[hives]2.9%4
Collapse2.2%3
Fever2.2%3
Oral ulceration2.2%3
Weakness2.2%3
Aggression1.5%2
Agitation1.5%2
Alopecia NOS[hair loss, type not specified]1.5%2
Bradycardia[slow heart rate]1.5%2
Convulsion[seizure]1.5%2
Mouth pain1.5%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

Dog0 · peak 1

Cat0 · peak 1

Horse0 · peak 1

Other0 · peak 1

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

Recovered/Normal0%0

Recovered with Sequela0%0

Ongoing0%0

Died20.4%28

Euthanized0%0

Outcome Unknown0%0

What kind of report it was

Safety issue100%137

Lack of expected effectiveness0%0

Both safety and lack of expected effectiveness0%0

Manufacturing or product defect0%0

Other0%0

Species

Horse96.4%132

Dog3.6%5

Age of the animal

Under 1 year2.2%3

1 to 3 years8%11

4 to 7 years14.6%20

8 to 11 years5.8%8

12 years and over9.5%13

Age not given59.9%82

Coloured bar: reports naming trichlorfon. 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	Trichlorfon	All reports
Reports	137	1,357,245
Latest 12 months against the 12 before	—	-5%
Classed serious, of reports stating it	0%	38.6%
Death or euthanasia recorded, per 1,000 reports	204.4	63.8
Filed as lack of expected effectiveness (wholly or partly)	0%	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 trichlorfon (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
Dyrex Bolus; Dyrex Granules	Trichlorfon	Zoetis Inc.	Horses	NADA 012-956
Freed No. 10; Freed No. 25	Atropine, Trichlorfon	Zoetis Inc.	—	NADA 013-248
Dyrex T.F - 1000; Dyrex T.F - 200; Dyrex T.F - 500	Phenothiazine, Piperazine Dihydrochloride, Trichlorfon	Zoetis Inc.	Horses	NADA 015-154
Dyrex Powder	Atropine, Trichlorfon	Zoetis Inc.	—	NADA 035-650
Equivet-14; Equizole-B	Thiabendazole, Trichlorfon	Farnam Companies, Inc.	Horses	NADA 091-067
Telmin B Equine Wormer	Mebendazole, Trichlorfon	Intervet, Inc.	Horses	NADA 100-402
Benzelmin Plus Paste	Oxfendazole, Trichlorfon	Zoetis Inc.	Horses	NADA 136-740
Telmin B Paste	Mebendazole, Trichlorfon	Intervet, Inc.	Horses	NADA 138-954
Anthon Horse Wormerapproval voluntarily withdrawn	Trichlorfon	Bayer HealthCare LLC, Animal Health Division	—	NADA 015-161
Purina Bot Controlapproval voluntarily withdrawn	Trichlorfon	Purina Mills, Inc.	—	NADA 048-915
Combot Equine Anthelminticapproval voluntarily withdrawn	Trichlorfon	Bayer HealthCare LLC, Animal Health Division	—	NADA 095-078
Combot Paste; Negabot Pasteapproval voluntarily withdrawn	Trichlorfon	Bayer HealthCare LLC, Animal Health Division	—	NADA 100-201
Combotel; Negabot Plus Pasteapproval voluntarily withdrawn	Febantel, Trichlorfon	Bayer HealthCare LLC, Animal Health Division	—	NADA 131-412

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 trichlorfon reports

How many FDA adverse event reports mention trichlorfon?

137 reports through March 2026, 0 of them in the latest 12 months, counting trichlorfon 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 trichlorfon without any counts.

In which combinations is trichlorfon reported?

Mebendazole + Trichlorfon (54.7% of these reports), Febantel + Trichlorfon (21.2% of these reports), Phenothiazine + Piperazine + Trichlorfon (13.1% of these reports) and Oxfendazole + Trichlorfon (10.9% of these reports).

What reactions are reported for trichlorfon?

abdominal pain (56.2%), diarrhoea (37.2%), death (17.5%), hypersalivation (17.5%) and anorexia (16.8%). Shares are of reports naming the ingredient; one report can list several terms.

Which animals are these reports about?

horse (96.4%) and dog (3.6%).

Does a high count mean trichlorfon 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.