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Vicodin (500) (Hydrocodone bitartrate-5 and acetaminophen-500): a 10 mg oral dose of hydrocodone administered to five adult male subjects = serum half-life of 3.8 ± 0.3 hours. Elimination should be in vicinity of 28 hrs.

It should be noted that the window of detection is not equivalent. More specifically, metabolites (breakdown components, spec. hydromorphone) result and can be detected across a longer period.

More specific information may be of obtained at:
http://www.rxlist.com/vicodin-drug.htm or http://www.drugs.com/vicodin.html