Dunno, folks ... I've asked our Doc Mike about these mail-order "bargins" ...
and he repeats the same cautions:

* If the price is only a couple dollars less, WHY bother?
* If the price is a LOT less - he'll guarantee it's not the "same stuff" as he sells!

Both Doc and the Staff Girls have had clients bring in the meds they've "mail-ordered" -
and the Packaging is NOT the same as the known Brand Name drug!
They showed a less than half price Heartgard Plus to the Factory Rep ...
He pointed out the many differences in the packaging graphics, then they looked
at the "chewies" ...
Not even a faint resemblance to the Real Thing!
"No WAY those things came from the Merial production line!" he said.

Doc has assured me the same things happens with the Flea & Tick meds ...
you only get the REAL Name Brand stuff if you PAY for it!

I've read of enough well documented cases of "knock-offs" being sold to make
me value the "extra cost" to buy from my Vet and KNOW the FurKids are really
getting what they need.

And that Same Doc Mike has NEVER had a problem telling me to go to Wally's World
and buy a generic, over-the-counter drug when he feels it's suitable!
And he's written scripts to have filled at WalMart when the plain ole Human drug
will work or be the same as the "high-priced Vet flavour" he has to sell is.

/s/ Phred