I have not had any problems with this dewormer at all. it is one of the best, and safest around. Safeguard is the exactly the same (both have fenbendazole as the main igredient), you can also give that. It comes in powder form, and you can mix it in their food.
There is another great dewormer called Nemex or Coopers Best. The main ingredient is Pyrental Pamote. That is also a very safe product as well. It comes in liquid form, so it is very easy to administer. Just use a syringe. It is very palatable, so they usually take it with ease.
I like to rotate with both every deworming.
I have to be careful on what I give my dogs, because they are working breeds and cannot have certain medications, such as Ivermectin.
I also worm my puppies every 3 weeks until 6 months of age as a preventative, because where I live, they need it.
Animals, what animals? My children just have alot of hair!