I also believe it is 24 hours. Why are you asking if you don't mind me asking? Are you trying to make sure it is in your system for a test? If your in pain management and take the Hydrocodone as prescribed then you should have no problem with the medication showing up in your blood work. Unlike UA tests the blood work will be accurate.
I believe it's 12-18 hours...not 100% sure though
I believe it's 24hrs.
BUT don't quote me on that. :)