What 1.34 Million FDA Animal-Drug Adverse-Event Reports Reveal
An analysis of 1,340,077 adverse-event reports from the FDA Center for Veterinary Medicine openFDA database (1987–2026): species breakdown, top reactions, serious outcomes, and reporting trends.
The FDA's Center for Veterinary Medicine (CVM) has been collecting adverse-event reports for animal drugs since the late 1980s. The resulting dataset — over 1.34 million individual reports spanning 1987 through early 2026 — is one of the largest post-market surveillance resources in veterinary medicine. It is publicly available through the openFDA API.
This article is a data analysis, not a clinical guide. Every number below comes from a direct computation of the openFDA animal adverse-event dataset (analysis run date: 2026-06-09). The goal is to show what the reporting volume, species distribution, reaction patterns, and outcome trends look like at scale — and to explain what a pharmacovigilance database can and cannot tell you.
What this database actually is
The FDA CVM Adverse Event Reporting (AER) system receives reports from veterinarians, animal owners, drug manufacturers, and other health-care professionals when an animal (or a human exposed to an animal drug) experiences an adverse reaction or a product failure. Manufacturers are required by law to submit reports they receive; voluntary reports come through the FDA Safety Reporting Portal.
Key limitations to keep in mind:
Reports are not confirmed causalities. A report means someone suspected a connection between a drug and an event. It does not mean the drug caused it.
Reporting volume reflects market share, awareness, and regulatory activity, not just risk. A widely used drug will accumulate more reports than a niche one, even if both have similar safety profiles.
Under-reporting is significant. Studies of human and veterinary pharmacovigilance systems consistently estimate that only a fraction of adverse events are reported.
Brand names are masked in the public dataset. Analysis is done by active ingredient.
The species breakdown
Of the 1,340,077 reports, the species distribution is dominated by companion animals:
| Species | Reports | Share |
|---|---|---|
| Dog | 974,175 | 72.7% |
| Cat | 145,155 | 10.8% |
| Unspecified | 144,513 | 10.8% |
| Cattle | 31,093 | 2.3% |
| Horse | 18,126 | 1.4% |
| Human (exposure) | 16,740 | 1.2% |
| Pig | 2,604 | 0.2% |
| Sheep | 1,069 | 0.08% |
| Chicken | 1,062 | 0.08% |
| Goat | 831 | 0.06% |
Dogs account for nearly three-quarters of all reports. This is unsurprising given the size of the pet population, the volume of prescriptions for canine parasiticides and therapeutics, and the visibility of companion-animal drugs to both veterinarians and owners who file reports.
Notably, 16,740 reports involve human exposure to animal drugs — a reminder that accidental human contact with veterinary pharmaceuticals (particularly topical parasiticides and large-animal injectables) is a recurring safety concern tracked by the FDA.
How serious are these reports?
The dataset flags each report as "serious" or not, based on whether the event resulted in death, a life-threatening condition, hospitalization, or a similar criterion.
Serious adverse events: 335,650 reports (25.0%)
Non-serious: 1,004,427 reports (75.0%)
Three-quarters of reports describe non-life-threatening events — vomiting, lethargy, transient diarrhea, or product-palatability complaints. The remaining quarter captures outcomes with greater clinical weight.
Outcomes at a glance
Each report can list one or more outcomes:
| Outcome | Count | % of reports |
|---|---|---|
| Outcome Unknown | 303,225 | 22.6% |
| Recovered/Normal | 278,459 | 20.8% |
| Ongoing | 224,816 | 16.8% |
| Died | 66,364 | 5.0% |
| Recovered with Sequela | 32,003 | 2.4% |
| Euthanized | 19,692 | 1.5% |
About 1 in 5 reports (20.8%) end with full recovery. Roughly 1 in 6 (16.8%) are ongoing at the time of reporting. Death is listed as an outcome in 66,364 reports — 5.0% of the total — and euthanasia in 19,692 (1.5%). Combined, fatal outcomes (Died or Euthanized) appear in approximately 85,693 unique reports (6.4%).
The top 15 reported reactions
Because a single report can list multiple reactions, the counts below exceed 1.34 million. The reaction terms follow the Veterinary Dictionary for Drug Regulatory Activities (VeDDRA) coding:
| Reaction | Count |
|---|---|
| Vomiting | 211,773 |
| Diarrhea | 81,061 |
| Lethargy | 76,425 |
| Emesis | 69,391 |
| Ineffective — heartworm larvae | 69,276 |
| Lack of efficacy — flea | 62,106 |
| Anorexia | 59,204 |
| Lack of efficacy — NOS | 55,141 |
| Lack of efficacy — heartworm | 51,520 |
| Death | 50,560 |
| Lack of efficacy — hookworm | 49,019 |
| Depression | 42,346 |
| Seizure (NOS) | 32,845 |
| Ataxia | 31,584 |
| Accidental exposure | 30,837 |
Gastrointestinal signs dominate the top of the list. "Lack of efficacy" entries — which represent suspected product failures, not adverse reactions in the traditional sense — collectively account for a very large share of the database. Heartworm lack-of-efficacy and ineffective-heartworm-larvae reports together total over 120,000 entries, a signal volume we examine in a separate analysis.
Most-reported active ingredients
The top ingredients by report count:
| Active ingredient | Reports | Fatal reports | Fatal rate |
|---|---|---|---|
| Spinosad | 206,522 | 5,159 | 2.5% |
| Milbemycin oxime | 182,072 | 4,645 | 2.6% |
| Ivermectin | 118,426 | 4,048 | 3.4% |
| Pyrantel pamoate | 89,876 | 1,835 | 2.0% |
| Moxidectin | 74,377 | 3,791 | 5.1% |
| Selamectin | 61,977 | 2,104 | 3.4% |
| Praziquantel | 54,542 | 1,787 | 3.3% |
| Afoxolaner | 53,081 | 1,682 | 3.2% |
| Carprofen | 50,978 | 8,676 | 17.0% |
| Fluralaner (chew) | 35,502 | 1,166 | 3.3% |
The parasiticide class dominates by volume. Spinosad (an oral flea treatment), milbemycin oxime (heartworm/flea preventive), and ivermectin together account for over half a million reports. Much of this volume reflects the enormous market penetration of monthly parasiticides combined with the "lack of efficacy" reporting category rather than acute toxicity.
Carprofen stands out: at 50,978 reports it has a 17.0% fatal-report rate — substantially higher than the parasiticides. This reflects both the drug's widespread long-term use in geriatric dogs with multiple comorbidities and the nature of the conditions it treats (osteoarthritis, post-surgical pain), where underlying disease progression contributes to adverse outcomes.
The 1987–2026 reporting trend
Annual report volume tells a story about regulatory infrastructure and market growth, not just drug safety:
| Period | Annual volume | Context |
|---|---|---|
| 1987–1993 | ~1,000–1,300 | Early voluntary reporting; limited digital infrastructure |
| 1994–1999 | ~3,000–11,500 | Growth of the parasiticide market; early online portals |
| 2000–2009 | ~18,000–40,000 | Post-market surveillance expansion; more manufacturer reports |
| 2010–2017 | ~43,000–77,000 | Peak years; openFDA launch increased transparency and access |
| 2018–2023 | ~58,000–72,000 | Slight decline, possibly reflecting stabilized reporting norms |
| 2024 | 81,145 | Second-highest year on record; new product introductions |
| 2025 | 74,386 | Partial year (dataset current through early 2026) |
The steep ramp from the 1990s through the 2010s coincides with the introduction of major parasiticide franchises (isoxazolines, spinosad-based products), the growth of pet insurance (which requires more documentation), and the FDA's push to make the data publicly accessible. The 2024 spike aligns with new monoclonal antibody therapies (bedinvetmab for canine OA pain) entering the market and generating fresh reporting activity.
Who files these reports?
The primary reporter breakdown:
| Reporter type | Count | Share |
|---|---|---|
| Other | 601,835 | 44.9% |
| Animal owner | 331,563 | 24.7% |
| Veterinarian | 234,207 | 17.5% |
| Other health-care professional | 165,195 | 12.3% |
| Patient (human) | 2,891 | 0.2% |
Nearly a quarter of reports originate from animal owners — a much higher proportion than in human pharmacovigilance, where direct patient reporting is less common. Veterinarians account for 17.5%, and other health-care professionals (veterinary technicians, pharmacy staff) contribute 12.3%. The "Other" category includes manufacturer-initiated reports, which are mandatory and often batch-submitted.
What the numbers mean — and what they don't
What this database is good for:
Identifying signal clusters — reactions that appear disproportionately for a given ingredient or species.
Tracking reporting trends over time, which can flag new safety concerns.
Understanding the volume of reported product failures (especially parasiticides), which is relevant to resistance monitoring and compliance discussions.
What this database cannot tell you:
The true incidence rate. Without a reliable denominator (how many doses were administered), you cannot calculate the probability of a reaction per dose.
Causality. A report is a temporal association, not a proof that the drug caused the event.
Comparative safety between drugs. A drug with 100,000 reports and 50 million doses administered may be safer than one with 1,000 reports and 100,000 doses — but the denominator is usually unknown.
The FDA itself emphasizes this point in its public documentation: adverse-event report data "cannot be used to calculate incidence rates or estimates of drug risk" because reporting is voluntary (except for manufacturers), subject to biases, and incomplete.
Related analyses in this series
This article is the first in a series analyzing the FDA CVM adverse-event dataset. Other analyses examine:
Reported heartworm and parasite preventive failures
Fatal outcomes and which species and ingredients carry the highest fatal-report rates
Species-specific profiles (equine, bovine, feline)
The most-reported veterinary drug ingredients and what drives pharmacovigilance volume
Sources
FDA Center for Veterinary Medicine. "Adverse Event Reports for Animal Drugs and Devices." https://www.fda.gov/animal-veterinary/product-safety-information/adverse-event-reports-animal-drugs-and-devices
FDA. "openFDA Animal & Veterinary Adverse Events API." https://open.fda.gov/apis/animalandveterinary/event/
FDA CVM. "FDA Posts Adverse Event Report Data for Animal Drugs and Devices Used in Animals to Increase Transparency." https://www.fda.gov/animal-veterinary/cvm-updates/fda-posts-adverse-event-report-data-animal-drugs-and-devices-used-animals-increase-transparency
FDA. "How to Report Animal Drug and Device Side Effects and Product Problems." https://www.fda.gov/animal-veterinary/report-problem/how-report-animal-drug-and-device-side-effects-and-product-problems
FDA. "Veterinary Adverse Event Reporting for Manufacturers." https://www.fda.gov/animal-veterinary/report-problem/veterinary-adverse-event-reporting-manufacturers
Data source: FDA CVM animal drug adverse-event reports (openFDA), downloaded 2026-06-09; analysis run date 2026-06-09. 1,340,077 individual reports, covering original receive dates from January 1987 through June 2026.
