Hi My Baby Is 5 Months Old And Having Cough

hi my baby is 5 months old and having cough from last one week i havr given maxtra drops 0.5 ml for 5 days and now started mucolite from yesterday 0.4 ml but nothing is working, doctor now suggested asthalin syrup as 2.5 ml, is it okay to give cough syrup to baby and is the dosage is okay