Frontline is sold over the counter now and is effective as a preventive in most cases, but for an infested cat/household, Vectra (only sold by veterinarian) is a superior product. Any flea that jumps on the cat will die within hours. A good vacuum (throw out bag or empty contents immediately) and an application of a good product on each cat in household is all you need to do. Continue the flea treatment for the rest of the summer to stop the reproduction cycle of any remaining fleas and you should be all set. Yes, the cat may now get tapeworm from ingesting a flea. Easy fix with one dose of medication from your vet. Any prescription only product sold online has been diverted and you just don't know where this product has been or who may have tampered with it. We have seen terrible results at our practice from medications that were purchased other than a licensed veterinarian's clinic. If you purchase the medication through your veterinarian, you then have the resource of going back to the company if there is ever a problem. Not so, if you purchase somewhere else because they cannot guarantee where it came from.