I copied this from another site:
Serious Side Effects and Death from Advantix
May 18th, 2003, by Teresa Schliker
There is a serious danger to pets from a new pest prevention medication. In addition to Advantage, Bayer has another flea/tick application on the market called "Advantix". It is being advertised heavily to the general public and pushed to clinics by sales reps, but more and more veterinarians are reporting serious side effects and even death among dogs. This medication is highly toxic and can adversely affect the nervous system. One of the active ingredients is a drug that most veterinarians phased out years ago because of these very risks.
Some of the side effects that veterinarians and pet owners are reporting are death, tremors, loss of motor control, vomiting, inability to tolerate touch, diarhea and unusual behavior. These may occur hours or more than a day afterward. Owners are reporting that this has happened even if the ointment was applied properly (behind the base of the skull where the dog cannot lick it). The incidence of serious side effects does not seem to be rare and many veterinarians are alarmed. They have pulled it off their shelves or let it expire so the sales reps will need to take it back, but in many cases they can face lawsuits for not participating in promotions as advertised (for example, giving away a free sample of Advantix with other products by Bayer).
If your dog or cat shows ANY signs of reaction to Advantix, bathe it immediately and take it to your veterinary emergency clinic. Suitable alternatives to Advantix are Advantage (also by Bayer), FrontLine, and FrontLine Plus.
Bayer is denying that the product normally has more than minor side effects even though it admits it has not adequately tested this drug. Sales reps are denying they've heard of the problem and literally laughing at veterinarians. You MUST report all incidents to the FDA if there is any hope of forcing a recall of the product. Please see the "Links" page to report an adverse reaction to the FDA.
If you want to see what I am talking about, go back to "Articles" and click "Advantix - I HATE IT"...this is a link to a thread in a veterinary technician magazine, mostly visited by veterinarians and technicians. There are more threads on that forum regarding Advantix."