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Hi,
The difference between these 3 meds is that they each contain different opioids of varying potency, in addition to APAP.
1) Darvocet contains Dextro-propoxyphene, a Methadone-derivative, which is the weakest opioid amongst the 3. Unfortunately it's also the most toxic. It's potency is roughly 2/3 to equal that of Codeine (1/20th the strength of Morphine). Also, for smokers it requires double the dosage to get the same effect due to the chemicals in cig smoke partially inhibiting the enzyme that metabolizes this drug).
2) Vicodin contains Hydrocodone which is about 1/4th the strength of Morphine. (40mg Hydrocodone = 10mg Morphine)
3) Percocet contains Oxycodone, the strongest opioid amongst the 3. It's potency is equal or slightly more than that of *parenteral / injected* Morphine. (10mg Oxy = 10mg Morphine IM or 30mg oral Morphine)
Hope this helps.
AJ
NB: I would personally rate Darvocet as one of the worst opioids. In addition to it being toxic, it's analgesic effect is dubious (patients respond equally well to 600mg of aspirin compared with 65mg Propoxyphene HCl.)
Also note that Darvocet comes in 2 forms. Propoxyphene HCl & Propoxyphene Napsylate. 65mg of the HCl salt = 100mg of the Napsylate salt. For reasons beyond the scope of this question, the Napsylate version is an almost total waste of money in that it hardly provides much pain relief.
Source(s):
Pharmacology & De-addiction specialist