I am pretty sure it would depend on 1. if they are reguler takers of these meds, or have just started to take them,2. what there personal tolerances are and reactions are to medications. It is quite possible for someone to still be feeling the effects for 24 hrs. I read that it is usually excreted from the system in 12 hrs but I did read of a case where a woman had halucinations etc for 3 days after stopping it, the
morphine had exacerbated an underlying condition they and she didn't know she had.
I am NOT a specialist or professional but do personally take MsContin tables (Morphine sulphate) and with long term use I have no more effect from it now than most people would get from panadol (except it helps my pain more), I do not suffer any side effect and I take it was numerous other medications.
Good Luck on finding an answer, but as everyone is different the only real way to tell would be to have the medications given to him again under medical supervision to see what effect it has on him (this woiuld not work if he is taking it long term as the human body does get used to it (this does NOT make people addicts, it is NOT an addiction it is a dependance on the medication to control pain levels, and people can usually be weaned off it with NO effect, depending again on the person, dose and length of time on it).
Shazinoz