This is my first order with this company and my first trial of Tri-Heart Plus. I usually use Heartgard but my vet doesn't carry it anymore so he wanted me to try Interceptor. My chihuahua has had reactions to several medications so I'm cautious as to what I give her. After giving her the Interceptor for 2 months, each time she would be listless for a few days, just not her usual self. So I found this med. I checked the ingredients (the same ingredients and same amount) as the Heartgard, it had good reviews and a great price. I consulted with my vet. He agreed to authorize the prescription for Tri-Heart Plus and I am "entirely pleased." I will be reordering.