Why 4 hours since ingestion changes the approach
The Baytril has already been absorbing during those hours, which means the vomiting you're seeing isn't an early warning—it's confirmation the drug is affecting your cat's system. At 4.2 kg, 2 mL of liquid formulation represents a significant exposure, especially since cats are particularly sensitive to fluoroquinolone toxicity compared to dogs.
Check her pupils under normal room lighting—fluoroquinolones can cause retinal damage visible as unusually dilated pupils that don't constrict properly. This would be an emergency finding requiring immediate veterinary intervention.
The overnight monitoring checklist
Set alarms every 2 hours to check for these specific signs: new vomiting episodes (count them), abnormal vocalization, or sudden clumsiness. Cats often mask discomfort until symptoms become severe, so subtle changes in behavior matter more than obvious distress.
Keep her in a dimly lit space—bright light could worsen any developing eye issues. Fluoroquinolones affect feline eyes differently than canine, with retinal toxicity being a particular concern at lower doses than would affect dogs.
Why mild vomiting isn't reassuring
What appears as 'mild' vomiting now could represent the first wave of gastrointestinal irritation before neurological symptoms appear. Cats process fluoroquinolones differently than dogs, with slower absorption but longer tissue retention—meaning effects may emerge gradually over 12-24 hours.
Watch the vomit for blood (bright red or coffee-ground texture) and note whether she's still interested in food. Unlike dogs, cats often stop eating entirely when nauseated by medications, which can quickly lead to secondary complications.
The critical 24-hour window
Even if she seems better by morning, retinal damage can develop insidiously over several days. Schedule a follow-up eye exam within 72 hours regardless of symptom resolution—fluoroquinolone toxicity sometimes manifests as delayed vision problems.
Document her water intake precisely; increased urination could indicate kidney stress from the medication. For an indoor cat without access to outdoor water sources, measuring what she drinks from her bowl provides essential data for your vet.
The step-by-step response, from the first minute to the vet visit, is in our Fluoroquinolone Antibiotic Poisoning in Dogs and Cats emergency guide.