What Are The Side Effects Of Mucolite Medicine?

My daughter undergone cleft pallete surgery 5 months back and Tympanostomy to her ears 4 months back.After Tympanostomy ENT doctor prescribed for giving mucolite syrup twice in a day regularly along with some vitamin syrup.She is having that medicine since that day. Last week when we consulted doctor again he told us to continue the medicine for another 4 months.But in the same case another ENT doctor not prescribed any medicine for my friend child.I am more worried because the continuous usage of mucolite medicine harmful for child health in future. please advise me