100% against.
Scientifically, testing products meant for humans on animals is unreliable and potentially dangerous. Animals react differently to humans to many substances, rendering many tests pointless. For example, a contraceptive called Tamoxifen was once developed which was tested on rats. It worked as intended, and was given to humans. However, it had the opposite effect on women, actually increasing their fertility!
There are many other examples, some of which had much more harmful consequences. You may remember Thalidomide, a drug given to pregnant women to prevent morning sickness. It had been tested on animals and declared safe for humans, but it caused severe deformities in many of the babies born after their mothers had taken it. A couple of years ago a drug called TGN1412 was tested on some human volunteers, and very nearly killed them - they were on life support for some time, and were left with permanent health problems. Prior to being given to these people, this drug had already been tested on monkeys at a dose 500 times stronger than that which was given to the humans, without causing the monkeys any ill effects. Aspirin causes birth defects in cats. Penicillin kills guinea pigs. 6-azauridine, a cancer drug which can be used in humans for long periods, will kill dogs in a few days in even small doses. The list goes on.
I don't believe in exploiting animals for any reason.