It takes between 8 and 24 hours for anaesthetic drugs to work their way out of a pet’s system. During this time, different behaviours can be noticed. Every pet is different: some will be barely affected, and bouncing around like nothing happened; others will be very sleepy and groggy, even wobbly on their feet; still others will appear restless, anxious, may be whiny or more vocal than usual, and seem unable to settle, perhaps more clingy than usual. All of these things are normal. You may see a small amount of coughing or heavy swallowing in the first 24 hours after procedures that involved an endotracheal tube being placed to help your pet breathe during anaesthesia, this is normal.