Your vet will usually diagnose permethrin poisoning based on the clinical signs, or a known history of permethrin exposure.
If required, management starts with decontamination. Decontamination is done by washing your cat to remove any residual permethrin. This may have been done at home, but if appropriate your vet will do this at the clinic.
As cats with permethrin poisoning suffer from twitching, muscle tremors and fits, these must be controlled by pharmaceuticals. These pharmaceuticals may be in the form of muscle relaxant or anti-seizure medications, and sometimes sedation or general anaesthesia is required to support control. As well as these pharmaceuticals, in very severe cases, a lipid infusion may be given which may help remove permethrin from body tissues.
Your vet will also start supportive treatment for your cat, in the form of giving intravenous fluids (a drip), nursing care and temperature monitoring. Permethrin poisoning is very serious, and cats who survive can take several days of intense care to recover.
If you think your cat may have ingested antifreeze, please contact your local Vets4Pets immediately.