What Does That Really Mean?
Norwegian Forest Cat = Rare
When veterinarians or drug companies tell cat owners that adverse reactions to Zorbium® are “rare,” this single word carries enormous weight in decision making. But what does “rare” actually mean in a medical context, and is it an accurate description for Zorbium®’s safety profile?
Medical Definitions of “Rare”
In pharmacovigilance (drug safety monitoring), regulatory agencies define adverse event frequencies as follows:
| Term | Medical Definition | Numerical Frequency |
|---|---|---|
| Very common | ≥ 1/10 | More than 10% |
| Common | ≥ 1/100 to < 1/10 | 1% to 10% |
| Uncommon | ≥ 1/1,000 to < 1/100 | 0.1% to 1% |
| Rare | ≥ 1/10,000 to < 1/1,000 | 0.01% to 0.1% |
| Very rare | < 1/10,000 | Less than 0.01% |
When a veterinarian describes an adverse event as “rare,” they should be indicating a frequency between 1 in 1,000 and 1 in 10,000 animals. But for Zorbium®, is this characterization accurate?
FDA Guidance on Rare, Serious Reactions
The FDA provides specific guidance on how rare but serious adverse events should be handled. While their published guidance primarily addresses human medications, it illustrates the regulatory approach to severe adverse events:
“For serious adverse events that are unusual in the absence of drug therapy (e.g., liver failure, agranulocytosis, rhabdomyolysis, idiopathic thrombocytopenic purpura, intussusception), there is a basis to believe there is a causal relationship between the event and the drug at a very low rate of occurrence. Therefore, these events are generally listed in the adverse reactions section even if there are only one or two reported events, unless it is clear that a causal relationship can be excluded.”
— FDA Guidance for Industry: Adverse Reactions Section of Labeling for Human Prescription Drug and Biological Products (FDA.gov)
This indicates that even with very few reports of serious outcomes like death, regulatory agencies consider these significant enough to disclose in product information.
The Missing Denominator Problem
To determine if adverse events are truly “rare,” we need two numbers:
- The number of adverse events reported
- The total number of administrations (the denominator)
For Zorbium®, we know there have been at least 366 cat deaths reported to the FDA since its approval in 2022. What we don’t know is the total number of administrations. – as of 8/26
Without this denominator, claiming adverse events are “rare” is scientifically unfounded.
Reported vs. Actual Adverse Events
According to widely cited estimates in pharmacovigilance — including data referenced by the FDA — voluntary adverse event reporting systems may capture only 1–10% of actual incidents. This means that for every reported death or adverse effect, there could be 10 to 100 unreported cases.
If the 366 reported deaths represent only 10% of actual fatalities — a reporting-rate assumption commonly cited in human pharmacovigilance research on passive adverse event systems — the true number could be closer to 3,660. At a more conservative 1% reporting rate, that figure rises to 36,600. These are illustrative extrapolations, not measured estimates specific to veterinary drugs — no published study establishes an equivalent underreporting rate for the FDA’s veterinary (CVM) adverse event system. What we can confirm directly: the word ‘rare’ does not appear anywhere in Zorbium®’s FDA-approved label — not in the adverse reactions section, not anywhere in the full prescribing information.
When “Rare” Means Fatal
Updated Analysis: August 2026
Even if an adverse event is statistically “rare,” the severity matters tremendously. A 0.1% chance (1 in 1,000) might sound small, but when the outcome is death, this represents a significant risk that deserves serious consideration.
Our most recent review of FDA adverse event data confirms 366 deceased cats and 5 dogs (preliminary, as of July 3, 2026) associated with Zorbium®. This figure comes directly from FDA reports coded as ‘Death,’ ‘Found Dead,’ or similar terms.
Our own analysis, based on 136 reported cases submitted voluntarily to ZorbiumLawsuit.com (up from our earlier count of 71), shows:
- 57 of 136 cases resulted in death (41.9%)
- 74 of 136 cases (54.4%) were off-label use — meaning Zorbium® was given for something other than post-surgical pain, its only FDA-approved use
- Cats given Zorbium® off-label died at 47.3%, compared to 35.5% for cats who received it for its approved surgical purpose
- Only 5 of 136 owners (3.7%) recall being told by a veterinarian that Zorbium® carried a risk of serious side effects or death before it was administered
With 366 FDA-confirmed deaths and rising, Zorbium®’s adverse event rate continues to far exceed the “rare” disclosure threshold. Per EMA guidance, “rare” means a frequency between 1 in 1,000 and 1 in 10,000. https://zorbium.com/what-if-elanco-is-right/
A pattern in coat color
Black and black-and-white cats make up just over half of all cases submitted to date (69 of 136, 50.7%) — and account for 32 of the 57 deaths reported, more than half.
Within our dataset:
| Group | Deaths | Total | Death rate |
|---|---|---|---|
| Black / black-and-white | 32 | 69 | 46.4% |
| All other colors combined | 25 | 67 | 37.3% |
This is voluntary, owner-reported data. It does not prove causation, and it has not been independently studied. But a pattern that has held steady — and strengthened — as our case count has grown from 71 to 136 submissions is a pattern that deserves real scientific investigation, not dismissal.
When your vet says “rare,” consider asking:
- “What is the specific risk percentage for adverse events?”
- “Was my cat’s case reported to the FDA?”
- “Is Zorbium® being used for its FDA-approved purpose, or off-label?”
- “Were you made aware this drug carries a risk of death?”
Data sources: FDA adverse event reports (through Q1 2026, preliminary) and 136 case submissions to ZorbiumLawsuit.com as of August 2026. Voluntary reporting carries inherent limitations, similar to the FDA’s own passive adverse-event surveillance system.
Testing Limitations
Zorbium® was primarily tested on young, healthy cats. According to reports we’ve received, testing focused on cats up to age 5 for post-surgical pain management. There are claims that the cats tested were, in fact, veterinarians’ own cats.
However, our data shows:
62.6% of adverse event reports with a known age involve cats 8 years or older (107 of 136 cases report an age)
54.4% involve off-label use for conditions other than post-surgical pain
When a drug is used in populations different from those in which it was tested, “rare” side effects may become more common.
The Bottom Line
“Rare” should never mean “not worth discussing” or “not worth considering,” especially when lives are at stake. True informed consent requires understanding both the likelihood AND severity of potential outcomes.
When it comes to your pet’s health, you deserve complete information – not reassurance based on vague terminology.
Sources:
Zorbium® adverse event data analysis from reports submitted to ZorbiumLawsuit.com (March 2024 – August 2026)
FDA Guidance for Industry: Adverse Reactions Section of Labeling for Human Prescription Drug and Biological Products (FDA.gov) – Note: While this guidance is for human medications, it illustrates the general FDA approach to serious adverse events reporting.
“Underreporting occurs with most adverse event reporting systems. The frequency of reporting for a given drug product varies over time, and may be greater when the drug is newly marketed, or when media publicity occurs.”
— FDA Center for Veterinary Medicine, Adverse Event Data, captured 4/8/2025
Data parsing and statistical calculations for this page were assisted by AI tools. Analysis, interpretation, and conclusions are the author’s own