I disagree with animal experiments. First of all,  animals results cannot be reliable. Though animal physiology is similar to humans, not all the studies can be extrapolated to humans. For example, animals cannot think, show other psychological symptoms as humans. So any testing for medicine  or drugs on animals will not be sufficient to equate with human subjects. Also animals have high metabolic activity than humans, so they can tolerate high doses compare with  humans. Second, Animal experiments are not easy. The animals like rats, mice may even bite the experimenters. Furthermore when experiments are run for long time like week or months, even years, animals may die in between. So the experiments can be hindered easily. Thank you for reading my opinion!