What Causes A Racy Heart Rate After Taking Single Dose Of Hydrocodone?

I have used hydrocodone for many years as well as abusing them. I lay in bed all night and most of the day. I plan on getting off and will be doing so with the help of my doctors. I gave my parents my medication so I wont abuse them. I just had carpal tunnel and bone fusion surgery. I was given percocets for pain. I took one and my heart rate is very fast and been so for hours. This has happened recently before when I was abusing. Why is it happening when I only take one and is there concern? When I abused the medication I also had problems with breathing, that is why I gave up control. Im not having problems breathing now but if I have pain and take another I might. What can I do?