What Was Documented in Original Studies vs. What Has Been Reported
The original FDA approval documents and Elanco’s marketing materials acknowledged certain effects of Zorbium®, but the FDA adverse event database shows a much broader and potentially more serious range of reactions. This page has been updated with the latest adverse event data through March 2025.
It is imperative that you report adverse events to both Elanco, who by law, must report adverse events within 10 days to the FDA. You are also on a recorded line. ***Veterinarians are not required to report adverse events.*** It is voluntary.
Summary of Latest Data (Updated October 2025)
Total Reports: 2816 adverse event reports
Total Animals Affected: 208
Species Distribution:
- Cats: 187 reports
- Dogs: 1 report
- Humans: 3 report
- Horse: 1
Most Common Adverse Events
- Staggering
- Restlessness
- Cat panting (unlike dogs, cats do not normally pant so this is a serious sign)
- Constant grooming
- Red or purple gums
- Sweaty feet
- Lethargy
- Vomiting
Cats have been reported pawing or rubbing at their water dish and water. As if the drug burns.
Based on VedDRA terminology, the most frequently reported adverse events include:
- Hyperactivity
- Dysphoria –
- Behavioral disorder NOS –
- Not eating –
- Hyperthermia –
- Dilated pupils –
- Application site reactions –
Now Reported to FDA:
- Behavioral disorder NOS (Not Otherwise Specified)
- Lethargy
- Dysphoria
- Hiding
- Hyperactivity
- Restlessness
- Agitation
- Disorientation
- Ataxia
- Seizures
- Mental impairment
- Circling
- Anxiety
- Excitation
- Loss of consciousness
- Confusion
- Twitching
- Pacing
- Staring
- Vocalization
- Hallucination
Temperature Regulation
Originally Documented:
- Hypothermia (94.7% of cats)
- Hyperthermia (74.3% of cats)
- Mean body temperatures “slightly above normal range”
Now Reported to FDA:
- Hyperthermia (high body temperature) – 7 reports affecting 14 animals
- Fever – 3 reports affecting 4 animals
- Elevated temperature – 3 reports affecting 3 animals
- In some cases, potentially contributing to severe outcomes
Cardiovascular and Respiratory Effects
Originally Documented:
- Hypotension (44.2%)
- Hypertension (37.2%)
- Tachycardia (28.3%)
- Bradycardia (30.1%)
Now Reported to FDA:
- Respiratory distress
- Heavy breathing
- Panting – 2 reports
- Decreased heart rate – 2 reports
- Laboured breathing
- Low blood pressure
Gastrointestinal Effects
Originally Documented:
- Constipation (noted in some study cats)
- Anorexia (22.1%)
- Diarrhea (9.7%)
Now Reported to FDA:
- Not eating – 8 reports affecting 9 animals
- Diarrhea – 2 reports affecting 4 animals
- Anorexia
- Nausea
- Drooling
- Not drinking
- Decreased appetite
Severe Outcomes
Originally Documented:
- No deaths during clinical studies
- Three cats removed due to hyperthermia
The Significance of These Differences
The original clinical studies were conducted under controlled conditions with:
- Healthy cats between 4 months and 5 years old
- Cats weighing between 2.6-16.5 lbs
- Exclusion of cats with renal, hepatic, cardiac, or respiratory disease
- Exclusion of pregnant or lactating cats
The much broader range of adverse events now being reported to the FDA suggests that:
- Real-world usage includes cats with different health statuses and conditions
- Some effects may be more severe or prolonged than observed in clinical studies
- The relationship between observed effects (like temperature dysregulation) and serious outcomes warrants further investigation
This data highlights the importance of comprehensive post-marketing surveillance and the value of the FOIA process in bringing this information to light for veterinarians and pet owners.
Reporting Adverse Events
If you observe adverse events after using Zorbium®, please report them to:
- FDA Center for Veterinary Medicine: 1-888-FDA-VETS
- Manufacturer: Call Elanco at +1-800-428-4441 or +1-888-545-5973
Data Source: FDA adverse event reports collected through December 2024. Last updated: October 12, 2025