First 48 hours at home: watching for rebound symptoms
Your cat may seem improved after hospital treatment, but the drug can linger in her system, causing symptoms to flare again unexpectedly. Set up a confined recovery space with low platforms—if she tries to jump and misses, it suggests returning neurological impairment. Check her pupils every two hours with a flashlight; uneven constriction means the toxin is still active.
Hydration is crucial but challenging—offer ice chips or diluted chicken broth if she refuses water. Count her breaths while resting; rapid shallow breathing (over 40/minute) could indicate the drug is affecting her diaphragm. Keep other pets away, as noise or movement may overstimulate her recovering nervous system and trigger tremors.
Managing appetite changes post-overdose
Don't be alarmed if she skips 1-2 meals—nausea is common after heartworm medication overdose. Warm her food slightly to enhance the smell, but avoid fish flavors if she received activated charcoal, as the contrast may deter eating. Hand-feeding small bits of plain boiled chicken can help rebuild her appetite gradually.
If she hasn't eaten by the 24-hour mark, contact your vet—prolonged fasting risks hepatic lipidosis, especially in a 4 kg cat. They may prescribe anti-nausea medication or recommend syringe-feeding a recovery formula. Monitor her litter box closely; diarrhea or unusually small stools suggest gastrointestinal irritation from the toxin or treatments.
Behavioral changes during recovery week
Expect personality shifts—some cats become clingy after overdoses, while others hide aggressively. Both are normal stress responses. Provide hiding spots like cardboard boxes with towels, but ensure they're easily accessible if she's still unsteady. Nighttime disorientation is common; leave dim nightlights near her sleeping area to prevent startle-related falls.
Play should resume slowly—if she normally enjoys chasing toys, introduce them only after 3-4 days, watching for coordination issues. Sudden bursts of running then stumbling indicate her nervous system isn't fully recovered. Avoid laser pointers entirely during this period—the frustration of unattainable prey may exacerbate neurological stress.
When to call the vet again
Any recurrence of twitching, jaw chattering, or uncontrolled vocalization means the drug's effects are reemerging—don't wait to see if it passes. Similarly, squinting or apparent blindness (walking into walls) warrants immediate callback. These signs often appear before full seizures develop.
Schedule a follow-up blood test around day 7 to check liver enzymes—even asymptomatic cats can have organ stress after overdoses. Mention any subtle changes like increased thirst or altered sleeping patterns—these help your vet assess whether long-term medication adjustments are needed for her heartworm prevention going forward.
The step-by-step response, from the first minute to the vet visit, is in our Heartworm Preventative Overdose emergency guide.