How long does Darvocet stay in your system?

Within 6 to 12 hours after taking Darvocet, half of the drug is excreted, according to Drugs.com. Propoxyphene, one of the main ingredients in Darvocet, produces a metabolite called norpropoxyphene. Half of the norpropoxyphene is removed from the body 30 to 36 hours after a dose of Darvocet.

Darvocet sometimes stays in the system much longer, depending on the person's age and other medical conditions, notes Drugs.com. Grapefruit juice and certain medications may also cause higher blood levels of Darvocet. Darvocet contains a combination of propoxyphene napsylate and acetaminophen that is prescribed to relieve mild to moderate pain. Patients are advised not to take Darvocet with antidepressants, antihistamines, alcohol or tranquilizers.