Cypermethrin (like other permethrin/pyrethroid compounds) is toxic to cats because of the deficiency of enzyme glucuronidase. So that dosages which are otherwise therapeutic in dogs lead to poisoning in cats.

Toxicity of cypermethrin depends strongly on the cis:transisomer ratios (usually 80:20; 40:60; 25:75), whereby the cisisomers are biologically more active but also more toxic than the trans isomers.

Besides neurotoxic effects, cypermethrin has also hepatotoxic effects and induces microsomal enzymes in the liver.

Major clinical signs in cats include:

• Tremors/muscle fasciculations (86%)
• Twitches (41%)
• Hyperaesthesia (41%)
• Seizures (33%)
• Pyrexia (29%)
• Ptyalism (24%)
• Ataxia (24%)
• Mydriasis (19%) and
• Temporary blindness (12%)

In these picture we see a cat showings signs of cypermethrin toxicity 6 hours after being shampooed with a cypermethrin based cleanser. The cat was attended by Dr Qazi Mudassir who successfully treated and cured the condition.