when the corrugated boxes are cleared as packing box of your medicine, you dont have to show it seperately and maintain formalities for it,
take cenvat credit of corrugated boxes, and utilise the same in clearance of your medicines , at the time of clearance, you have to declare on ARE-1, under mode of packing as "corrugated boxes" also in packing list.
balance corrugated boxes is your input, and you are not trading the same but using the same as inputs for paking of your final products, hence dury credit is available to you.
for clearance of packing products in which your medicines are packed, you dont need to mtaintain seperate export formalities, but it will be part of your medicine clearance only,