What Can I Do if the Pharmacy Gave Me the Wrong Prescription?

On 2nd Nov, when I went to get medicine for my daughter (6 Years) with the doctor’s original prescription, the pharmacist at one of the big chain of the medical store has dispensed the wrong medication. Instead of kids medicine, he has given adult one though it was clearly mentioned on prescription. WE have given medicine for two days trusting that medicine given by trained pharmacist will be right until we have seen some reaction for two days and when I did some research by my self I realize we were giving wrong (higher dose) medicine. I am really disappointed for their casual behaviour and want to make a case as my daughter is very sensitive and had open heart surgery when she was 3 months old. Let me know what are my rights and what is the best way to handle this? FYI, when I spoke to their senior managers they were apologetic but not very concern about any legal complications. Thanks, Rupesh Tela