The amdrodil S syrup is a combination syrup which has Levosalbutamol in it. The Duonil respule has a combination of Salbumatol and other drug. So if you continue the syrup and nebuliser you will be giving same class of drug through oral and nebulised route. I would recommend having a review by a doctor and consider one route instead of syrup and nebulisation after physical examination of the chest with a stethoscope. That way you will avoid overdoing things. If it was a basic cough syrup without salbutamol, then nebulisation on top would be ok. Wishing him a speedy recovery