Active ingredient · pooled across combinations
Estradiol Benzoate: adverse event reports, pooled
6 ingredient sets in reports · 7 FDA-approved applications in the Green Book
Estradiol Benzoate appears, alone or combined with other ingredients, in 659 reports in FDA's animal adverse event database (May 1990 to March 2026). The figures here pool all 6 ingredient sets that include it.
The Green Book lists 7 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.
30 reports arrived in the 12 months to March 2026, down 33% from 45 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 18 reports a year over its reporting history and 0.1% of all reports.
Pooled across every set, the terms listed most often are death (17.9%), increased sexual interest (17%) and implant, Abnormal (12.1%). 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, 43% were classed as serious (38.6% across the whole database); 24.1% 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 estradiol benzoate
| Active ingredients recorded for the drug | Reports | Share of this page's reports | Latest 12 months |
|---|---|---|---|
| Estradiol Benzoate + Trenbolone Acetate | 342 | 51.9% | 21 |
| Estradiol Benzoate + Progesterone | 290 | 44% | 6 |
| Estradiol Benzoate + Testosterone Propionate | 30 | 4.6% | 2 |
| Estradiol Benzoate + Progesterone + Tylosin Tartrate | 9 | 1.4% | 2 |
| Estradiol Benzoate + Testosterone + Tylosin Tartrate | 5 | 0.8% | 0 |
| Estradiol Benzoate | 4 | 0.6% | 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 estradiol benzoate reports listing the termall reports in the database
- Death17.9%118
- Implant, Abnormal12.1%80
- Device Defective NOS[a product quality report, not a sign in an animal]6.8%45
- Sexual disorder NOS[NOS: not otherwise specified]6.5%43
- Containers, Damaged[a product quality report, not a sign in an animal]5.6%37
- Underfilling, Package[a product quality report, not a sign in an animal]4.9%32
- Lack of efficacy - NOS[the product did not have the expected effect]4.4%29
- Anaphylaxis[sudden severe allergic-type reaction]4.1%27
- Ineffective, weight inc[legacy FDA term: the product did not have the expected effect (weight inc)]3.6%24
- Death by euthanasia[the animal was euthanized]2.7%18
- Dyspnoea[difficulty breathing]2.7%18
- Underfilling, Container[a product quality report, not a sign in an animal]2.6%17
- Recumbency[lying down and unable or unwilling to rise]2.4%16
- Implant site abscess2.1%14
- Aggression2%13
- Containers, Abnormal[a product quality report, not a sign in an animal]2%13
- Hypersalivation[drooling]2%13
- Increased weight2%13
- Behavioural disorder NOS[behaviour change, type not specified]1.8%12
- No sign[no clinical sign was reported]1.8%12
- Rectal prolapse1.8%12
- Lameness1.7%11
- Tablets, Abnormal[a product quality report, not a sign in an animal]1.7%11
- Vaginal prolapse1.7%11
- Lack of efficacy (bacteria) - NOS[the product did not have the expected effect: target not specified]1.5%10
- Mammary gland disorder NOS[NOS: not otherwise specified]1.5%10
- Dispenser, Abnormal[a product quality report, not a sign in an animal]1.4%9
- Mammary hyperplasia1.4%9
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 estradiol benzoate. 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 | Estradiol Benzoate | All reports |
|---|---|---|
| Reports | 659 | 1,357,245 |
| Latest 12 months against the 12 before | -33% | -5% |
| Classed serious, of reports stating it | 43% | 38.6% |
| Death or euthanasia recorded, per 1,000 reports | 241.3 | 63.8 |
| Filed as lack of expected effectiveness (wholly or partly) | 7.1% | 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 estradiol benzoate (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 |
|---|---|---|---|---|
| Synovex C | Estradiol Benzoate, Progesterone | Zoetis Inc. | Cattle | NADA 009-576 |
| Synovex H | Estradiol Benzoate, Testosterone Propionate | Zoetis Inc. | Cattle | NADA 011-427 |
| Component E-C with Tylan; Component E-S with Tylan; Component E-C | Estradiol Benzoate, Progesterone, Tylosin Tartrate | Elanco US Inc. | Cattle | NADA 110-315 |
| Synovex Choice; Synovex Plus; Synovex Primer | Estradiol Benzoate, Trenbolone Acetate | Zoetis Inc. | Cattle | NADA 141-043 |
| Synovex ONE Feedlot; Synovex ONE Grower | Estradiol Benzoate, Trenbolone Acetate | Zoetis Inc. | — | NADA 141-348 |
| Celerinapproval voluntarily withdrawn | Estradiol Benzoate | PR Pharmaceuticals, Inc. | Cattle | NADA 141-040 |
| Celerin Capproval voluntarily withdrawn | Estradiol Benzoate | PR Pharmaceuticals, Inc. | Cattle | NADA 141-041 |
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 estradiol benzoate reports
How many FDA adverse event reports mention estradiol benzoate?
659 reports through March 2026, 30 of them in the latest 12 months, counting estradiol benzoate 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 estradiol benzoate without any counts.
In which combinations is estradiol benzoate reported?
Estradiol Benzoate + Trenbolone Acetate (51.9% of these reports), Estradiol Benzoate + Progesterone (44% of these reports), Estradiol Benzoate + Testosterone Propionate (4.6% of these reports), Estradiol Benzoate + Progesterone + Tylosin Tartrate (1.4% of these reports) and Estradiol Benzoate + Testosterone + Tylosin Tartrate (0.8% of these reports).
What reactions are reported for estradiol benzoate?
death (17.9%), increased sexual interest (17%), implant, Abnormal (12.1%), device Defective NOS (6.8%) and sexual disorder NOS (6.5%). Shares are of reports naming the ingredient; one report can list several terms.
Which animals are these reports about?
cattle (65.7%), human exposure (1.5%) and horse (0.8%).
Does a high count mean estradiol benzoate 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.