The common cold
medication do have medication which can slow the activities in general population. Many times the sedative activity of anti histaminics present in cold medications is some much powerful that it can produce drowsiness
and decrease activity.
Apart from that syrups for cold medication also have alcohal in them which may be causing these thing.
Now it is important to understand that the severity of these condition is not very much high with these drugs and once you stop the medication these things should also go away.
I would suggest you to consult your doctor as your condition is different as you are recovering from lubar sugery and need proper evaluation to make it confirm that it is not related to any neurological condition.
Thanks and take care.