I have 5 cats all of which are strictly indoor and well taken care of. I found worms coming out of one of my kittens butt 2 weeks ago and the vet gave me medication for Tapeworms to apply to the back of her neck to rid her of them. Today I noticed them again... they are white and small (about the size of rice) and the end where the head is I suppose, is flat. They look exactly like Tapeworm segments. Why didn't the medication work 2 weeks ago when I treated her? I was specifically given medication for Tapeworms. Also, would all of my cats have these worms as well if one does? I only notice them on her...
Sounds like it could be tapeworms again. Sometimes it takes 2 doses of the dewormer to work. It is also possible that your cats were infected again. When a dewormer is administered to a pet, it is only in the system for around a day. It is possible that you applied the dose and the cat was infected the next day.
Did your vet explain how cats get tapeworms? In order for a cat (or dog) to get a tapeworm, they have to ingest a flea. Therefore, flea protection is very important. Even for indoor cats. Every time you go outside you could be tracking in flea eggs that have dropped off of stray animals and/or wildlife in your yard. If there is one flea in the environment there is a problem. An adult flea is only 5% of the population with 50% comprising of the eggs.
I would suggest you call your vet and explain you think your kitty has tapeworms again and discuss a good flea control.