Is There Any Other Condition That Would Show Signs Of

Is there any other condition that would show signs of overdose, other than overdose? My son had an incident yesterday that has been resolved, but the hospital doc said he may have overdosed on his medications, but I do not believe this to be true or possible. He has neuro issues (Spina Bifida and Hydrocephalus) Shunt looked good. He presented with shallow breathing, tiny pupils and unconsciousness. He had had an infusion treatment two days before this incident (IVIG) for CIDP. I am just trying to figure out what other possible cause there could be other than overdose. I am his Parent CNA and know for certain that his meds were distributed and taken correctly. Thank you for your thoughts.