It is not uncommon when starting psych meds to have to take some time to find the right one(s). Different people react differently to meds and a reaction can occur for no apparent reason.

I take anti-depressants and it took some time to find one that works for me. (Lexapro and Celexa made me throw up. Imiprimine was a miserable experience. Zoloft and/or Wellbutrin are fine.)

He might tolerate another drug much better than this one.

At the same time, I'm not medicating my son because his symptoms are manageable without medication and I don't want to go through the medication adjustment process with a kid. Adjusting my meds was a very unpleasant process for me. I don't think the benefit of meds outweighs the costs for my son. (Again, his ADHD symptoms are mild. YMMV.)