Estradiol Benzoate + Trenbolone Acetate (Synovex): adverse event reports that FDA received

Name: Estradiol Benzoate + Trenbolone Acetate: adverse event reports that FDA received, by year and species
Creator: Pet Drug Reports
License: https://creativecommons.org/publicdomain/zero/1.0/

Combination of 2 active ingredients

The name in brackets is a brand name with these active ingredients.

The openFDA records give the value "MSK" for the brand name and for the manufacturer name of each drug. FDA says that MSK means "masked". So the site cannot count a report for a brand.

Read this first. FDA says this about the data:

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 publishes these words. Source: Adverse Event Reports for Animal Drugs and Devices, read on 2 Oct 2026. The data have the reports that FDA received through 26 Jun 2026.

This page is not veterinary advice. For an animal that is ill, speak to a veterinarian.

Contacting a veterinarian How to report to FDA

From June 2014 to June 2026, FDA received 344 adverse event reports that name this drug. Its active ingredients are estradiol benzoate and trenbolone acetate. Of the 344 reports, 234 (68%) are about cattle.

In January to March 2026, FDA received 7 reports that name this drug. The signs that appear in the largest number of the 344 reports are "Increased sexual interest", "Death" and "Sexual disorder NOS". A report is not proof that a drug caused a sign.

Reports that name this drug fell by 34.4% in the 12 months to June 2026, compared with the 12 months before. Reports for all animal drugs fell by 4.6% in the same periods. The newest months can get more reports in a later update. Reports about cattle are 68% of the reports that name this drug, and 2.3% of all reports.

Search engines list a drug page with 500 reports or more in all years. The page also needs 30 reports or more in the 12 months to June 2026. This page is under one of these numbers. The site keeps the page and keeps it out of search engines.

Since the last update of the FDA data

The latest update of the FDA data, recorded on 11 Oct 2026, changed no count of this page.

January to March 2026 is the latest closed quarter in the data. In that quarter FDA received 7 reports that name estradiol benzoate + trenbolone acetate: 0 dog, 0 cat, 0 horse, 7 other or not given.

All updates Feed of updates (RSS)

Signs that the reports list

A sign is a coded term from the report. The words in brackets are a plain gloss of the term. The percentage is the share of the 344 reports that list the sign. One report can list more than one sign.

The sign that is in the largest number of the reports comes first.

Increased sexual interest27.3%94 reports
Death14.2%49 reports
Sexual disorder NOS[NOS: not otherwise specified]11.3%39 reports
Device Defective NOS[a product quality report, not a sign in an animal]9.6%33 reports
Containers, Damaged[a product quality report, not a sign in an animal]8.7%30 reports
Implant, Abnormal8.4%29 reports
Lack of efficacy - NOS[the product did not have the expected effect]4.9%17 reports
Increased weight3.8%13 reports
Death by euthanasia[the animal was euthanized]3.5%12 reports
Underfilling, Container[a product quality report, not a sign in an animal]2.9%10 reports
Aggression2.6%9 reports
Implant site abscess2.6%9 reports
Anaphylactic-type reaction2.3%8 reports
Behavioural disorder NOS[behaviour change, type not specified]2.3%8 reports

Show the next 16 signs

Lameness2.3%8 reports
Color, Abnormal[a product quality report, not a sign in an animal]2%7 reports
Musculoskeletal disorder NOS[NOS: not otherwise specified]2%7 reports
Rectal prolapse2%7 reports
Tablets, Abnormal[a product quality report, not a sign in an animal]1.7%6 reports
Vocalisation[crying out or unusual noise]1.7%6 reports
Containers, Abnormal[a product quality report, not a sign in an animal]1.5%5 reports
Necropsy performed1.5%5 reports
Vaginal prolapse1.5%5 reports
Administration device NOS, damaged1.2%4 reports
Anaphylaxis[sudden severe allergic-type reaction]1.2%4 reports
Difficulty of Use[a product quality report, not a sign in an animal]1.2%4 reports
Found dead1.2%4 reports
Limping1.2%4 reports
No sign[no clinical sign was reported]1.2%4 reports
Penile protrusion1.2%4 reports

The list shows 30 of 170 coded signs. A report is not proof that a drug caused a sign. Download all signs (CSV)

Reports by species

Cattle68%234
Human exposure0.9%3

The share is of all 344 reports that name estradiol benzoate + trenbolone acetate. The other reports give a different species or no species.

Reports for each month, Jul 2021 to Jun 2026

Dog0 reports

No chart: no month has 5 or more reports.

Cat0 reports

No chart: no month has 5 or more reports.

Horse0 reports

No chart: no month has 5 or more reports.

Other or not given121 reports. Largest count in one month: 7 (Aug 2024)

The month is the month in which FDA received the report. Each chart has its own scale. FDA says that a report can take 3 to 6 months to reach the public data. The newest months can get more reports in a later update.

Reports by year

Dog
Cat
Horse
Other or not given

Reports that name estradiol benzoate + trenbolone acetate, by the year in which FDA received them and by species
Year	Other or not given	All species
2026	9	9
2025	21	21
2024	34	34
2023	26	26
2022	17	17
2021	22	22
2020	28	28
2019	26	26
2018	32	32
2017	38	38
2016	77	77
2015	12	12
2014	2	2

2026 has the reports that FDA received through Jun 2026. Download the years (CSV)

What the reports record

Outcome at the time of the report

Recovered/Normal8.7%30
Recovered with Sequela[recovered, with a lasting effect]2.6%9
Ongoing2.3%8
Died18.9%65
Euthanized3.8%13
Outcome Unknown50.6%174

An outcome in a report is not proof that the drug caused it. The person who sends the report gives the outcome. Each share is of the 344 reports that name estradiol benzoate + trenbolone acetate.

A report about more than one animal can have more than one outcome.

Kind of report

Safety issue61.3%211
Lack of expected effectiveness4.1%14
Both safety and lack of expected effectiveness1.5%5
Manufacturing or product defect33.1%114
Other0%0

237 reports say if the event was serious. 39.2% of them have the serious flag. The person who sends the report sets the flag.

Show age, weight, breed and route

Age of the animal

Under 1 year7.6%26
1 to 3 years8.7%30
4 to 7 years0.3%1
8 to 11 years0%0
12 years and over0.6%2
Age not given82.8%285

Weight of the animal

Under 5 kg (11 lb)0%0
5 to 9.9 kg (11 to 22 lb)0%0
10 to 24.9 kg (22 to 55 lb)0%0
25 to 44.9 kg (55 to 99 lb)0%0
45 kg and over (99 lb and over)50.3%173
Weight not given49.7%171

Breed, where the report gives one breed

Holstein-Friesian14%48
Aberdeen Angus2.9%10
Corriente0.3%1

A breed with many animals has many reports.

Route in the report

Subcutaneous20.1%69
Other0.3%1
Parenteral0.3%1

Each bar is on a scale of 0 to 100%.

Approved animal drugs with these active ingredients (FDA Green Book)

This section is reference data. It has no report count.

The openFDA records give the value "MSK" for the brand name and for the manufacturer name of each drug. FDA says that MSK means "masked". So the site cannot count a report for a brand.

Brand names

Synovex

What the Green Book records give

Applications with an approval in force: 2
Approved species: Cattle
Dose forms: Extended-release implants, Subcutaneous Implant, Implant
Routes: Subcutaneous
Sale: OTC (over the counter)
Earliest approval date in the records: 22 Feb 1996

The species, dose forms and routes are the words of the Green Book records for all the applications together. One product can have fewer. The label of a product gives its approved use.

Applications in the Green Book of 2 Nov 2026, pioneer applications (NADA) first
Brand name	Active ingredients	Sponsor	Approved species	Application
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.	Not in the list of major species	NADA 141-348

Other pages with one of these ingredients

A report names a drug by its set of active ingredients. Each set has its own page. The list is in order of name.

Next in the A to Z list

All drugs by active ingredient. Brand names A to Z

FDA pages for this drug

How to Report Animal Drug and Device Side Effects and Product ProblemsThe FDA page that tells an owner or a veterinarian how to send a report.
Green Book record of NADA 141-043The FDA record of the application for Synovex Choice, Synovex Plus, Synovex Primer.
Green Book record of NADA 141-348The FDA record of the application for Synovex ONE Feedlot, Synovex ONE Grower.
Animal Drugs @ FDAThe search page of the Green Book, the FDA list of approved animal drugs.

The site checked these addresses on 2 Oct 2026. The links open in a new tab.

Cite this page

Pet Drug Reports. Estradiol Benzoate + Trenbolone Acetate: adverse event reports that FDA received. https://petdrugreports.com/drug/estradiol-benzoate-trenbolone-acetate/ Source: FDA Center for Veterinary Medicine, openFDA Animal and Veterinary adverse event reports, export of 30 Oct 2026. Reports received through 26 Jun 2026.

Where the data come from

The counts come from the openFDA Animal and Veterinary adverse event files, export of 30 Oct 2026. The files have the reports that the FDA Center for Veterinary Medicine received through 26 Jun 2026. The files mask brand and manufacturer names. The site counts a drug by the active ingredients that each record gives, and gives no count to a brand, an application or a company. Ingredient names and the lists of approved products follow the FDA Green Book of 2 Nov 2026. The site does not use the application number that a record has.

The site does not publish report text, lot numbers or details of a reporter. FDA's record is the authority. See how the site counts reports, the data sources and the corrections page.

Questions about these reports

Which brand are these reports about?: The openFDA records give the value "MSK" for the brand name and for the manufacturer name of each drug. FDA says that MSK means "masked". So the site cannot count a report for a brand. The Green Book section of this page lists the brand names with these active ingredients.
Do the reports show that the drug caused the signs?: No. FDA states this about the data.
When looking at the results, be aware that there is no certainty that the reported drug or device caused the adverse event.
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. Source: Adverse Event Reports for Animal Drugs and Devices
How many reports did FDA receive in the latest 12 months?: FDA received 21 reports in the 12 months to June 2026. It received 32 reports in the 12 months before. FDA says that a report can take 3 to 6 months to reach the public data. The newest months can get more reports in a later update.
What kinds of report are in the count?: Of the 344 reports received from June 2014 to June 2026, 61.3% are about a safety issue only. 5.5% are about a lack of expected effectiveness, alone or with a safety issue. 33.1% are about a defect of the product or its package.