Hi
Thanks for the query to H C M .
As you mentioned that your son is having pain in the stomach ( mid ) , also nauseous ,
promethazine helped ( due to its anti emetic effect ).
This type of pain may be due to hyper acidity or
gastritis .
These measures may be helpful :
Try raising the head of your son bed about 4 inches with blocks.It also might help to avoid eating or drinking for 2-3 hours before he lie down .To help control stomach acid ( nauseous ) one should not drink alcohol or drinks with caffeine in them or eat chocolate or spicy or greasy foods .Also to take some
antacid but if symptoms are severe he may may need drugs like
pantoprazole 40 mg once in day on empty stomach for 5-7 days .
If symptoms recurs then consult a physician and get his opinion.
Hope this information will be useful for your son.
Further if any question I will reply.
Good luck .