Findlaw published an article today detailing a lawsuit against the manufacturer of Heartguard Plus that alleges the company fired her after she discovered "the company had intentionally utilized improper data analysis methods to ward off an FDA investigation."
She's not just any former employee, though. She's Dr. Kari Blaho-Owens, the former Global Head of Pharmacovigilance, which means she oversaw the collection and analysis of adverse reactions to drugs the company manufactured. Her lawsuit alleges that she discovered Heartguard Plus is not 100% effective, despite the company's claims otherwise, and that she was instructed to destroy documents that were relevant evidence in a class action lawsuit against the company.
Of course, her allegations are just that -- allegations. However, there are a few shady facts staining the company's reputation, including two FDA warning letters (one in 2007, available here). You can also read the earlier class action lawsuit against the company here.
Another article (scroll down) tells that when one dog contracted heartworm disease after being on Heartguard Plus, the company paid for the dog's treatment after investigating and finding that the owner's compliance with giving the preventative to her dog was substantial.