I suggest that mom does not discuss disagreement between parents on use of meds with the child. Instead, in curious, unemotional way, ask the child how he feels using the ADHD meds, how he feels not using meds. What is the difference? Don’t say “good” or “better” or “worse.” Ask for a description of how he feels and see what words he uses. Repeat those words back to him: Ask, “How do you like feeling….(use his words)? Give him the opportunity to show his preference. If he brings up “But Dad says,…” don’t react to “Dad” but say, “How do YOU feel?” Leave Dad out of it. Let him know you are open to conversation about medication and you accept his feelings about it. You may continue to give him meds, saying the doctors say this is good for you, but you have shown that it’s about his well-being not about a power struggle with Dad. You can repeat this conversation in a few weeks. It’s a start.