The brands mentioned contain pyrethrins or permethrins, both of which are extremely toxic to cats.
As you have already discovered, these cheap products, even if they don't kill the first time around, don't work, so you are wasting your money, and the next time you use it your cats may not be so lucky.
A six pack of frontline plus at the vet should cost about $80 or less, plus you get two free (manufacturer promotion) That is $10 per dose.
If you live in an area where winters are cold, depending on the level of infestation, 4-6 months of treatment with frontline plus, with a home program of daily vacuuming, and frequent laundering of cat beds and bedding, will get rid of the fleas permanently, as long as all pets are treated every 30 days, and they don't go outside, ever.
Declawing: please read this first
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