You may want to sit with your friend so you can pet and comfort her while the vet gives her the medicine. Many vets give the pet a shot of sedative before the euthanasia drug. The vet will explain to you what he's doing and where he's giving the shot. Some vets only use a sedative if the pet is frightened or can't relax. The shot can cause pain and the drug does have side effects, so talk to your vet about whether your pet should get it. If she's very sick and already quiet or has trouble breathing she may not need it.