What does the cat litter do?
I have not used this but do use API First Layer Pure Laterite which, if you read the label is the same basic material.It's just a cheap, readily available, inert clay-based substrate, and it has a high CEC (cation exchange capacity), this enables the substrate to temporarily 'hold' nutrients and such, and the plants can then 'take' the nutrients from the substrate.
Just make sure you get a basic, natural type, with no scents/colors/etc. Some types hold up okay, others turn to mush after being wet for a bit. Still good for plants, but can make a mess when disturbed.