Why Pfizer Doesn't Want the FDA Studying Its Diet Drug for Dogs

Last Updated Oct 15, 2010 4:29 PM EDT

Ignorance is bliss, if Pfizer (PFE)'s opposition to a small FDA study to see if certain dogs experience more adverse events on Slentrol, a weight-loss pill for hounds, is to be believed. Why would Pfizer not want to know whether certain genetic breeds of dogs react differently to the diet drug?

The company says the test is unwarranted:
Given that the majority of adverse reactions that have been received are consistent with mild labeled adverse reactions and that the breeds represented in these cases are consistent with breed popularity and the most commonly observed obese breeds, there does not appear to be any correlation between specific dog breeds and specific adverse events ...
The study underlines one of the chief concerns about the drug industry's rush into the pet-med category: Dogs and cats can't complain if they believe the drug is harming them. Even better, they can't get onto the Internet and inform other patients of the side effects they're experiencing. Sure, an owner can report physical or behavioral side effects to a vet, but she can't report mental side effects or internal organ changes that can't be seen with the naked eye.

This issue is particularly acute for Pfizer's Slentrol for three reasons:
  1. The FDA is leery of approving diet drugs for humans precisely because their side effects are often so weird.
  2. It's possible that side effects on pet meds are under reported because dogs can't talk.
  3. Three of Slentrol's major side effects are unhealthy responses that might also lead to weight loss: vomiting, diarrhea and anorexia. Click to enlarge this image of the Slentrol adverse reaction list:

Could it be that some dogs lose weight on Slentrol not because of its efficacy but because they feel so sick while taking it?

It's also interesting that the prescribing information indicates that the control group received corn oil but does not say that the Slentrol group received it. My local vet tells me there's no reason for a dog to receive corn oil, even if you're trying to make its coat shiny. There are dog food supplements for that. She did say, however, that corn oil would be a good way to give a dog diarrhea. Could it be that that diarrhea in the control group is overstated due to corn oil, making diarrhea in the Slentrol group look less dramatic by comparison?

Pfizer gave this reason for the corn oil:
Control dogs received corn oil to simulate Slentrol's oil-based carrier of its active ingredient (dirlotapide).
Which suggests to this layperson that if the dogs had been corn-oil free, like normal dogs, then the diarrhea side effect would indeed be much lower in the control group.

And finally: You could always give your dog less food and walk him more. Just a thought.

Related: Image by Flickr user Vandelizer, CC.