I do this all the time. My vet gave me a syringe marked with the amount for my cats. I buy the largest dog kind and give the recommended dosage to my dog and cats. I believe for my cats it is .8 ml, I just use the marked vials he gave me. I've been doing this for a few years and with 4 cats it has saved me lots of money. I can't speak for other flea medications and I know that Advantix is bad for cats but with Advantage it works very well.
I just got back form my vet with my cat. She is a 10.11 pound Main Coon and she said Advantage can be used on both but the dosage is very important. She gave me a plastic syringe and told me to only use 0.8 (ml?) from it and no more. She also said Frontline is different for dogs and cats so do not use the dog formula on cats.
Advantage - Yes
Frontline - No
I hear you sister. You are a kind soul. I'd give anything if more people were like you and if more people would get their pets fixed. We are the earth's keepers after all. I'm another sandwich person as well.
As far as the Advantage and Advantage II for dogs goes- they are safe for cats in the proper dose per cat's weight. I've been doing it for years like some of you.
Now Advantix and Advantage K9 for dogs are NOT to be used on cats because they are both toxic to them.
The other brands of flea meds I know nothing about-but if there's any chance at all that any of them can harm your pet DON'T take that chance.
Advantage yes; advantix no. Almost killed a cat once with advantix, but have had no problems with advantage.
The strength is the same. The amount you use is different.
DOGS: 2-10# .4cc
CATS: up to 9# .4cc
Over 9 # .8cc
If you buy the extra large tube for dogs (4.0cc) and put it in a small container you can use a syringe to draw up the amount you need to use according to their weight.