Recently had my pain dr change 15mg oxy prn to perc 10/325 prn, as the oxy's no longer worked. weaker strength percs helping prn. curious, as to why?

Oxy vs Percocet : Percocet is released into the circulation much faster than Oxycontin (if that's what your were on), which is one reason it be perceived as working better. Percocet's other ingredient, Acetaminophen acts in the brain similar to oxycodone, and its believed the potentiating effect of the combination is another reasons why Percocet may work better. Highly habit forming.