Most people appreciate a free sample. But at the dermatologist's office, that freebie might come with a hidden cost. A new study finds that giving out samples may actually change which drugs a doctor prescribes. Stanford University researchers looked at data from a national survey of office-based doctors, most of whom distribute samples. They found that doctors were more likely to prescribe medications if they also were distributing samples of those drugs. The researchers also compared doctors who gave samples to those at Stanford, an academic medical facility where samples aren't allowed. What they found was dramatic: Doctors who gave samples were giving patients more frequently prescribed brand-name drugs instead of cheaper generics.