Zeranol (Ralgro): adverse event reports that FDA received
Active ingredient
The name in brackets is a brand name with this active ingredient.
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 . The data have the reports that FDA received through .
This page is not veterinary advice. For an animal that is ill, speak to a veterinarian.
Contacting a veterinarianHow to report to FDAFrom November 1987 to November 2025, FDA received 596 adverse event reports that name a drug with zeranol as its active ingredient. Of the 596 reports, 163 (27.3%) are about cattle. 24 reports are about people who were exposed to the drug (4%).
In January to March 2026, FDA received no reports that name this drug. The signs that appear in the largest number of the 596 reports are "Implant, Abnormal", "Dispenser, Abnormal" and "Product Defect, General". A report is not proof that a drug caused a sign.
Fewer than 20 reports named this drug in the 12 months before June 2026, so this page gives no change. Reports about cattle are 27.3% 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 , changed no count of this page.
January to March 2026 is the latest closed quarter in the data. In that quarter FDA received 0 reports that name zeranol: 0 dog, 0 cat, 0 horse, 0 other or not given.
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 596 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.
- Implant, Abnormal34.7%207 reports
- Dispenser, Abnormal[a product quality report, not a sign in an animal]34.6%206 reports
- Product Defect, General[a product quality report, not a sign in an animal]18.8%112 reports
- Death12.1%72 reports
- Containers, Abnormal[a product quality report, not a sign in an animal]5.5%33 reports
- Vaginal prolapse4.5%27 reports
- Increased sexual interest3.5%21 reports
- Lack of efficacy - NOS[the product did not have the expected effect]3.2%19 reports
- Unclassifiable adverse event[event that fits no dictionary term]3.2%19 reports
- Accidental exposure[exposure that was not intended]2.9%17 reports
- Product problem[a product quality report, not a sign in an animal]2.9%17 reports
- Rectal prolapse2.7%16 reports
- Uncoded sign[a sign with no matching dictionary term]2.7%16 reports
- Device Defective NOS[a product quality report, not a sign in an animal]2.5%15 reports
Show the next 16 signs
- Mammary gland oedema1.8%11 reports
- Underfilling, Package[a product quality report, not a sign in an animal]1.8%11 reports
- Anaphylaxis[sudden severe allergic-type reaction]1.5%9 reports
- Lack of efficacy (bacteria) - NOS[the product did not have the expected effect: target not specified]1.5%9 reports
- Injection site pain[pain where the injection was given]1.3%8 reports
- Containers, Damaged[a product quality report, not a sign in an animal]1.2%7 reports
- Respiratory tract disorder NOS[NOS: not otherwise specified]1.2%7 reports
- Difficulty of Use[a product quality report, not a sign in an animal]1%6 reports
- Injection site swelling[swelling where the injection was given]1%6 reports
- Necropsy performed1%6 reports
- Anorexia[not eating]0.8%5 reports
- Behavioural disorder NOS[behaviour change, type not specified]0.8%5 reports
- Ineffective, weight inc[legacy FDA term: the product did not have the expected effect (weight inc)]0.8%5 reports
- Malaise[generally unwell]0.8%5 reports
- Pneumonia[lung infection or inflammation]0.8%5 reports
- Anaphylactic-type reaction0.7%4 reports
The list shows 30 of 167 coded signs. A report is not proof that a drug caused a sign. Download all signs (CSV)
Reports by species
The share is of all 596 reports that name zeranol. The other reports give a different species or no species.
Reports for each month, Jul 2021 to Jun 2026
No chart: no month has 5 or more reports.
No chart: no month has 5 or more reports.
No chart: no month has 5 or more reports.
No chart: no month has 5 or more reports.
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
| Year | Dog | Cat | Horse | Other or not given | All species |
|---|---|---|---|---|---|
| 2025 | 0 | 0 | 0 | 10 | 10 |
| 2024 | 0 | 0 | 0 | 7 | 7 |
| 2023 | 0 | 0 | 0 | 6 | 6 |
| 2022 | 0 | 0 | 0 | 4 | 4 |
| 2021 | 0 | 0 | 0 | 15 | 15 |
| 2020 | 0 | 0 | 0 | 9 | 9 |
| 2019 | 0 | 0 | 0 | 5 | 5 |
| 2018 | 0 | 0 | 0 | 1 | 1 |
| 2017 | 0 | 0 | 0 | 3 | 3 |
| 2016 | 0 | 0 | 0 | 10 | 10 |
| 2015 | 0 | 0 | 0 | 25 | 25 |
| 2014 | 0 | 0 | 0 | 18 | 18 |
| 2013 | 0 | 0 | 1 | 39 | 40 |
| 2012 | 0 | 0 | 0 | 32 | 32 |
| 2011 | 0 | 0 | 0 | 28 | 28 |
| 2010 | 0 | 0 | 0 | 27 | 27 |
| 2009 | 0 | 0 | 0 | 11 | 11 |
| 2008 | 0 | 0 | 0 | 35 | 35 |
| 2007 | 0 | 0 | 0 | 50 | 50 |
| 2006 | 0 | 0 | 0 | 53 | 53 |
| 2005 | 0 | 0 | 0 | 35 | 35 |
| 2004 | 0 | 0 | 0 | 9 | 9 |
| 2003 | 0 | 0 | 0 | 37 | 37 |
| 2002 | 0 | 0 | 0 | 11 | 11 |
| 2001 | 0 | 0 | 0 | 21 | 21 |
| 2000 | 0 | 0 | 0 | 2 | 2 |
| 1999 | 0 | 0 | 0 | 20 | 20 |
| 1998 | 0 | 0 | 0 | 4 | 4 |
| 1997 | 0 | 0 | 0 | 9 | 9 |
| 1996 | 0 | 0 | 0 | 8 | 8 |
| 1995 | 0 | 0 | 0 | 3 | 3 |
| 1994 | 0 | 0 | 0 | 1 | 1 |
| 1993 | 0 | 0 | 0 | 4 | 4 |
| 1992 | 0 | 0 | 0 | 3 | 3 |
| 1991 | 0 | 0 | 0 | 3 | 3 |
| 1990 | 0 | 0 | 0 | 4 | 4 |
| 1989 | 0 | 0 | 0 | 18 | 18 |
| 1988 | 0 | 0 | 0 | 9 | 9 |
| 1987 | 0 | 0 | 0 | 6 | 6 |
2025 has the reports that FDA received through Nov 2025. Download the years (CSV)
What the reports record
Outcome at the time of the report
- Recovered/Normal2.3%14
- Recovered with Sequela[recovered, with a lasting effect]0.2%1
- Ongoing3.4%20
- Died13.9%83
- Euthanized0.5%3
- Outcome Unknown3.9%23
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 596 reports that name zeranol.
A report about more than one animal can have more than one outcome.
Kind of report
- Safety issue28.2%168
- Lack of expected effectiveness4%24
- Both safety and lack of expected effectiveness0.5%3
- Manufacturing or product defect67.3%401
- Other0%0
69 reports say if the event was serious. 71% 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 year14.6%87
- 1 to 3 years3.2%19
- 4 to 7 years0%0
- 8 to 11 years0%0
- 12 years and over3.2%19
- Age not given79%471
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)0.7%4
- 45 kg and over (99 lb and over)20.1%120
- Weight not given79.2%472
Breed, where the report gives one breed
- Holstein-Friesian2.9%17
- Aberdeen Angus2.3%14
- Red Angus0.5%3
- Brangus0.3%2
- Cattle0.3%2
- Charolais0.2%1
- Hereford cattle0.2%1
A breed with many animals has many reports.
Route in the report
- Subcutaneous21.6%129
- Parenteral2.3%14
- Auricular (Otic)1%6
- Intra-Articular0.3%2
- Intramuscular0.3%2
- Oral0.3%2
Each bar is on a scale of 0 to 100%.
Approved animal drugs with this active ingredient (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
- Ralgro
What the Green Book records give
- Applications with an approval in force
- 2
- Approved species
- Cattle
- Dose forms
- Implant, Implants
- Routes
- Subcutaneous
- Sale
- OTC (over the counter)
- Earliest approval date in the records
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.
| Brand name | Active ingredients | Sponsor | Approved species | Application |
|---|---|---|---|---|
| Ralgro | Zeranol | Intervet, Inc. | Cattle | NADA 038-233 |
| Ralgro L. A. | Zeranol | Intervet, Inc. | Cattle | NADA 141-192 |
Next in the A to Z list
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 038-233The FDA record of the application for Ralgro.
- Green Book record of NADA 141-192The FDA record of the application for Ralgro L. A..
- Animal Drugs @ FDAThe search page of the Green Book, the FDA list of approved animal drugs.
The site checked these addresses on . The links open in a new tab.
Cite this page
Pet Drug Reports. Zeranol: adverse event reports that FDA received. https://petdrugreports.com/drug/zeranol/ Source: FDA Center for Veterinary Medicine, openFDA Animal and Veterinary adverse event reports, export of . Reports received through .
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 this active ingredient.
- 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 4 reports in the 12 months to June 2026. It received 7 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 596 reports received from November 1987 to November 2025, 28.2% are about a safety issue only. 4.5% are about a lack of expected effectiveness, alone or with a safety issue. 67.3% are about a defect of the product or its package.