Hi. Thank for your query. noted the history about your 3 year old son having continuous vomiting, was prescribed domstal, and asked to admit if he vomits. Your son vomited after 1 hour of having medicines. This means the vomiting has not stopped. Any small child , like the age of 3 should be admitted for a simple reasons as they can go into dehydration and electrolyte imbalance if the vomiting does not stop in spite of proper medication like Domperidone available as Domstal. He needs a proper clinical evaluation, examination and investigations as necessary. Get him admitted to the hospital and follow the advise of the pediatrician. Do not keep him at home as once the vomiting has stopped, he ill be discharges as per the on advise of the treating Doctor.