Welcome to health care magic. yes u can give lanzol jr sachet to ur child as per ur dr adviced. lanzole jr is prton pump inhibitor contain lansoprazole which reducing gastric acid secreation which mostly use in GERD , nausea, vomiting. Because of illness , it was avoid anything for ate . give him little around 2_3hourly dont worry its totally safe. most important part in this condition is rehydration , give him plenty of dinking water to avoid dehydration. if he/she have shruken eyes, dryness in tongue , irritable ,weakness , drowsiness then its serious one go to hospital for intravenous fluids. iam sure ur baby get well in few day . wish u get ur baby early recover from this illness Regards .