You are quite right, Jerry. I didn't fool you one bit! It is NOT our job -- or our authority -- to require someone to take medication. Moreover, it is not within our legal purview to deny a student with a disability the appropriate accommodation because we think he/she should be handling their disability differently. The key word in that sentence is "THEIR disability." Whether it is the student with a spinal cord injury whom we think would be more independent in a motorized, rather than manual, wheelchair or the student with ADHD who chooses not to take the medication prescribed, those are personal decisions on the part of the student.
You have also correctly identified one of the reasons that students with ADHD sometimes do not want to take the prescribed medication. The side effects can be both disorienting and debilitating for some folks. And I think you offered exactly the right response in suggesting that he return to the prescribing physician to have a talk about alternatives. It is important to keep in mind, however, that if the student's behavior or performance suffers during the time he is not on medication, he must still be held accountable for what he DID do, or DID produce. As is true with every other student, you must judge on the basis of your observations, not your expectations!