Horse strongid is exactly what my small animal vet uses to deworm cats in his office, (we watched him fill the syringes from the bottle) and since I usually have some on hand, that is what I use on my cats. Getting the weight right is the hard part, but I think it is pretty safe.
Lauralee thanks for the warning about cats and ivermectin (not that I would have tried it without knowing) I have known for a long time about the possible effects in collie breed dogs, but did not know about cats.