I've heard that, too, and even saw some literature from the company at my vet's that said that. I use Iverhart (sp?) for heartworm, and Advantage or Certifect for fleas. If your AB is white, there may be flea allergy and skin problems, too, so keep an eye out for that.

Thanks for the information. DH just left to return the Trifexis. This big boy is too nice to take a chance with making him very sick. I didn't know about white and flea allergies -- that's important to know.

I've had my close to 17 year old PON on Triflexis for four months now. I admit I was scared to death to try it as he is on a special diet, has had skin problems, and all the other problems with seem to go with an aged dog. However it has caused no problems for him, and seems to work fine so far.

Like any medication, some will have negative effects. Riley has been on TF for over 2 years without a problem. He's 6 now.