Drug profile
The FDA adverse-event record for Heartworm Prevention (Unknown)
987 FDA reports name Heartworm Prevention (Unknown), a high-volume drug in the CVM extract. Species, reactions, and outcomes follow.
- #183 of 2,679
- by report volume (all drugs)
- 987
- adverse-event reports
- 2.7%
- death-coded share
- Dog
- most-reported species
Corpus placement
According to the FDA Center for Veterinary Medicine openFDA adverse-event extract, Heartworm Prevention (Unknown) ranks #183 of 2679 by total reports (987) and #937 of 1130 by death-coded share (2.7%). National dual: Milbemycin Oxime + Spinosad is #1 of 2679 drugs by total adverse-event reports (149,624) at death-coded-share rank 965 of 1130 drugs with at least 50 reports (2.3%); separately, Atlantic Salmon Transgenic Whole (Opafp-Ghc2 Rdna Construct Inserted Into The A-Locus In The Eo-1A Lineage) is #1 highest death-coded share at 97.8% (report rank #821).
- 149,624
- Milbemycin Oxime + Spinosad reports (#1)
- 97.8%
- Atlantic Salmon Transgenic Whole (Opafp-Ghc2 Rdna Construct Inserted Into The A-Locus In The Eo-1A Lineage) death share (#1)
- #183
- This drug, reports of 2679
- #937
- This drug, death share of 1130
Report volume reflects how common a breed or drug is and how often owners and vets file — not actual risk. Death-coded share ranks are limited to entries with enough reports to be meaningful. The two maps do not agree at #1.
Release-over-release change
What changed in the latest FDA data snapshot
PlainBreed reconstructed the prior snapshot from dated openFDA partitions through 2025 Q4, then compared it with the 2026-07-27 openFDA export. Heartworm Prevention (Unknown) has 987 reports now versus 983 in that prior snapshot: 4 more (0.4%).
- Report change
- +4
- Death-coded reports
- +0
- Death-coded share
- −0.0 pts
This compares reported-event counts in two source snapshots. It does not establish a change in real-world risk, product safety, or disease incidence.
Subscribe to Heartworm Prevention (Unknown) changesSignature read: 987 reports place Heartworm Prevention (Unknown) in the upper third of FDA AER volume (#183 of 2,679).
Active Ingredients
Administration Routes
Species Affected
Most Affected Breeds
Most Reported Reactions
Outcome Breakdown
Heartworm Prevention (Unknown): low death-coded share in the FDA AER row
Read these counts as reporting volume, not risk: per our methodology, a widely-prescribed drug will rack up more raw FDA reports in a given year than a rarely-used one at an identical true rate, so we recommend comparing within similar-exposure products rather than across the full 2025 catalog.
High-volume nationwide drug peers
Two openFDA-derived peer sets for Heartworm Prevention (Unknown), both floored at ≥50 reports so the neighborhoods stay in the advertised mass.
Similar report volume
Nearest other drugs by FDA report count (987 here).
Similar death-coded share
Nearest other drugs by death-coded share (2.7% here), distinct from the volume row.
What to do with this drug
- Compare Heartworm Prevention (Unknown)'s report volume and death-coded share against similar drugs nationwide. See similar drugs
- Read how death-coded share differs from a mortality rate before drawing conclusions. Understanding adverse events
- Browse the full drug directory to compare report counts across products. All drugs
A report does not prove a drug caused the reaction; consult a veterinarian before acting on this data.
Source: FDA Center for Veterinary Medicine openFDA Animal & Veterinary Adverse Events (CVM AER) · 2025
Informational only. FDA adverse-event reports are voluntary and do not prove causation; consult a veterinarian before acting on them. Verify with FDA CVM →