How long does the acetaminophen and propoxylene stay in your system?

Acetaminophen is used for pain relief and to reduce a fever. Peak plasma levels are seen within 0.5 to 2 hours after taking the drug and it has a half life of 2 to 4 hours. (the time taken for the drug level in plasma to reduce by half)

Propoxyphene is a centrally acting narcotic pain reliever for mild to moderate pain. Peak plasma levels are seen after 2 to 2.5 hours of taking the drug and it has a half life of 6 to 12 hours.

For more information see : http://www.drugs.com/pdr/propoxyphene-napsylate-acetaminophen.html