Darvocet (Dextropropoxyphene also know as Propoxyphene) is a fully synthetic opioid analgesic (ie a narcotic). It is used to control mild pain and it is closely related to Demerol (Pethidine also known as meperidine). Darvocet is a mixture of Dextropropoxyphene and acetaminophen. Both drugs do reduce pain however the Dextropropoxyphene is the primary analgesic due to its opioid activity.
Darvocet has come under significant controversy because dextropropoxyphene is highly addictive and most countries only have medications containing both Dextropropoxyphene and acetaminophen. As a result there has been an alarmingly high incidence of death due to addicts taking so many pills that the acetaminophen becomes toxic and kills.
Dispite the high addictive potential of dextropropoxyphene, the US classifies it a a schedule IV drug along with Valium, Phenobarbital, and many others. Most opioid's are schedule II but codeine and hydrocodone drugs containing acetaminophen or an NSAID are schedule III.