Drug profile

The FDA adverse-event record for Melarsomine

939 FDA reports name Melarsomine, a high-volume drug in the CVM extract. Species, reactions, and outcomes follow.

#192 of 2,679
by report volume (all drugs)
939
adverse-event reports
3.4%
death-coded share
Dog
most-reported species

Corpus placement

According to the FDA Center for Veterinary Medicine openFDA adverse-event extract, Melarsomine ranks #192 of 2679 by total reports (939) and #890 of 1130 by death-coded share (3.4%). 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)
#192
This drug, reports of 2679
#890
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. Melarsomine has 939 reports now versus 924 in that prior snapshot: 15 more (1.6%).

Report change
+15
Death-coded reports
+0
Death-coded share
−0.1 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 Melarsomine changes

Signature read: 939 reports place Melarsomine in the upper third of FDA AER volume (#192 of 2,679).

Important: Adverse event reports do not establish that a drug caused or contributed to the event. Consult your veterinarian before making treatment decisions.
939
Total Reports
32
Deaths Reported
3.4%
Death-coded share of reports

Active Ingredients

Melarsomine

Administration Routes

IntramuscularUnknownParenteralOralOtherSubcutaneousIntravenous

Species Affected

Dog 910
Unknown 27
Cat 2

Most Affected Breeds

Retriever - Labrador 143
Crossbred Canine/dog 110
Dog (unknown) 60
Dog (other) 56
Beagle 52
Pit Bull 44
Shepherd Dog - German 44
Unknown 33
Chihuahua 32
Boxer (German Boxer) 19

Most Reported Reactions

Lack of efficacy (endoparasite) - heartworm 370
INEFFECTIVE, HEARTWORM LARVAE 240
INEFFECTIVE, HEARTWORM ADULTS 208
Cardiac disorder NOS 99
Lack of efficacy - NOS 86
Vomiting 63
Lethargy (see also Central nervous system depression in 'Neurological') 54
Other abnormal test result NOS 52
Injection site pain 43
Panting 31
Weight gain 30
Diarrhoea 29

Outcome Breakdown

Outcome Unknown
599 (65.5%)
Ongoing
113 (12.4%)
Recovered/Normal
94 (10.3%)
Recovered with Sequela
75 (8.2%)
Died
18 (2.0%)
Euthanized
15 (1.6%)

Melarsomine: 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 Melarsomine, both floored at ≥50 reports so the neighborhoods stay in the advertised mass.

Similar death-coded share

Nearest other drugs by death-coded share (3.4% here), distinct from the volume row.

What to do with this drug

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

openFDA Animal & Veterinary Adverse Events (FDA CVM) for Melarsomine (#192 of 2,679 by report volume); death-coded 3.4%. PlainBreed drug row · report volume stamp 939 · vintage 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 →