This is what is in a darvocet:
Propoxyphene napsylate, Acetaminophen
It is a very mild pain killer. Propoxyphene Napsylate and Acetaminophen are the ingrediants. They barely compare to the oxycodone and hydrocodone, but it is viable for pain.
They put 650mg of acetaminophen to keep you from taking them to get high. But it is such a weak synthetic opiate, you probably won't feel anything in comparison to the others who have taken.