Valerie Olszyk: I used to be a pharmaceutical representative for Merck Frosst Canada, and I believe they have a division that makes Heartgard, the drug you were asking about for heartworms. (If memory serves me correctly, that is. I do not know the generic name, so check to see that we are talking about the same thing. I was only involved in human pharmaceuticals.) A good way to enhance your knowledge of this drug on ferrets would be to call the company's American head office, located in Rahway, New Jersey. Their medical department is one of the best in the world for pharmaceuticals, and they should have the information readily available for you. The phone number may even be toll free (I'm writing from Canada, so I have no way of knowing.) I am told that Merck has a home page on the Internet that may also let you know what number to call to find out this information. I hope that helps. I know nothing about vet medicine, but I do know that the pharmaceutical company will have information on dosage, safety, half-lives of the drug, etc. They should even know for ferrets. If I am wrong, and Merck does not make this drug, then find out who does. If you do not get a response from Merck, please e-mail me at [log in to unmask] and I will go through Canadian channels for additional information. Good luck. From, Nancy, Sylvain, Farrah (the Edmonton, Alberta, Canada ferret) & Tashia (who is still without a second name!) [Moderator's note: Yes, Merck is the manufacturer. Trouble is that since use in ferrets is off-label use, I doubt they'll discuss dosages. Following is my understanding of it, but please confirm any details with a vet in the know...I'm neither a vet nor do I claim to always have a clue as to what I'm talking about :-) I think the proper dose for heartworm prevention is indeed quite low, like 10/mcg/kg. But dosages as high as 200-400 mcg/kg are used to treat other parasitic infestations such as ear mites, so the safe range is pretty broad. BIG] [Posted in FML issue 1357]