Can i give a 12 yr. old a promethegan suppository for nausea?

For vomiting: Yes but not more than 1-2 times/day, confirm the dose with pharmacist od your doctor and know the side effect. I would not use it just for nausea, only if there is recurrent emesis with no other concerning signs for intestinal obstruction disease e.G abdominal distension, bile in vomiting or signs of inflammation e.G blood in stools, vomitus.