Cat urine is notoriously difficult to clean because it has a component that many household cleaners are not equipped to remove. That component is uric acid. Because uric acid is not water-soluble, it bonds to any surface it touches. The only way to effectively break down uric acid and remove its smell permanently is to use an enzymatic cleaner.
How to Clean Cat Urine Out of a Mattress
Cleaning the Mattress
Remove all of the bedding from your mattress.
Blot up as much of the urine as you can with a dry towel.
Douse the soiled area of the mattress with the enzyme cleaner.
Let the enzyme cleaner soak into the mattress for 15 minutes.
Blot up as much of the enzyme cleaner as you can with another dry towel.
Let the mattress air dry as long as possible.
Cleaning the Bedding
Add laundry detergent and enzyme cleaner to the washing machine.
Add the sheets, blankets and bedding to the machine after the water fills.