I believe we're going to see this more and more with the increased focus on everything organic,anti-processed anything "all natural" everything movement. I can't tell you how many times I've heard, "I'm not putting chemicals in my child's body!" just this year alone. I actually had a parent of a child with severe behavior issues the other day tell me that she believes a self-contained behavior unit with 5 students and 6 adults would be "less restrictive" then keeping him in a general ed setting with medication. She wants to try the self-contained unit before trying medication.
As difficult as it is, I would never argue with parents who use that line of reasoning in the approach that you're trying to convince them to use medication. If they talk about getting their child off of it, just tell them not to do it against a doctor's advice. If you recommend a child seeing a medical professional and they make complaints about putting chemicals in their children, I would just state that you weren't giving any advice about medicine but just to talk to someone who has the ability to do so if needed. My dad is a pharmacist and when I was in grade school, what disturbed him the most was when teachers were making suggestions that I or other students should be put on a prescription medication.