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 282 cat deaths reported to the FDA since its approval in 2022. What we don’t know is the total number of administrations. – as of 12/24
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 282 reported deaths represent only 10% of actual fatalities, the true number could be closer to 2,282. At 1% reporting, that figure rises to 28,200. Rare is not defined in Zorbium® documentation.
When “Rare” Means Fatal
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 analysis of 71 reported cases from Zorbiumlawsuit.com shows:
- 49.2% resulted in death
- Consistent patterns of neurological and respiratory symptoms
- Nearly half involved off-label use
The FDA’s guidance specifically notes that serious adverse events should be listed “even if there are only one or two reported events.” With 282 reported deaths, Zorbium®’s adverse events far exceed this threshold for disclosure.
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:
- 70.8% of adverse event reports involve cats over 8 years old
- 49.2% 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.
Questions to Ask Your Vet
If your veterinarian suggests using Zorbium® and describes potential side effects as “rare,” consider asking:
- “What is the specific risk percentage for adverse events?”
- “How many cases of serious adverse events have been reported?”
- “Has Zorbium® been tested in cats with my pet’s specific health condition/age?”
- “What are the warning signs of an adverse reaction I should watch for?”
- “Are there alternative pain management options with better-established safety profiles?”
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 – April 2025)
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