My dog weighs 16 pounds so I used the 16-30 lb. Ultra Guard Flea and tick drops. About 7 days later she woke up but could barely walk and literally laid in the chair for two days. She is usually hyper when anyone comes in or if I ask if she wants to take a walk. Now she would not even lift her head. She couldn’t get down the steps of my deck, wouldn’t eat for three days and was just staring off in the distance. Do not use Hartz of any kind on any pet that you love. It is not worth it, I really thought she was going to die. She is just beginning to walk again but Lord only knows what kind of damage there has been to her liver or kidneys. I am spreading the word…DO NOT USE HARTZ, THEY CAN’T BE TRUSTED TO TAKE THIS PRODUCT OFF THE MARKET BECAUSE IT IS HARMFUL OR DEADLY TO ANIMALS SO THEY CAN’T BE TRUSTED WITH ANY PRODUCT IN MY HOME.