Did you tell your vet the pill your cat ate has acetaminophen in it?
Regardless, you need to get your cat to the vet NOW! Acetaminophen is
toxic to cats and hydrocodone in the dose you mention is  nearly 10
times what would be prescribed to a 10 pound dog. Don't wait. Go now!

Megan

                                   

Here is info that underlines your need to get to a vet quickly:

Treatment for acute acetaminophen toxicosis in cats include:

1)    Induction of vomiting followed by activated charcoal and a
saline cathartic if ingestion is recent (within 4-6 hours).

2)    Oxygen therapy if there is severe cyanosis.

3)    Intravenous or oral administration of acetylcysteine (140 mg/kg
as a 5% solution initially, followed by 70 mg/kg IV every 4 hours, for a
total of 4 to 6 treatments). Acetylcysteine provides cysteine required
for increasing synthesis of glutathione.

4)    Ascorbic acid (30 mg/kg orally) for treatment of
methemoglobinemia. Vitamin C should be given every 6 hours as needed.

5)    Fluid therapy for possible acidosis.

Megan

                                   

I hope everything worked out.  I would be more concerned about the 325 mg
of acetaminophen than the 10 mg of hydrocodone.  Acetaminophen is highly
toxic to cats.