Re: oxycodone compared to hydrocodone
As Brian wrote, it depends on how much oxycodone you were/are taking. Hydrocodone is weaker than oxycodone milligram for milligram. So, if you are on alot of oxycodone then you will experience some withdrawal.
Can you wean yourself off of the oxycodone slowly? That's the best solution, and augment the oxycodone with the hydrocodone and you build up to whatever that dose should be.
FYI - Hydrocodone is prescribed along with acetaminophen (APAP), usually with 5mg of hydrocodone and 500mg of APAP. Some formulas have as much as 7.5 to 10mg of hydrocodone, and the APAP can range from 325mg to 750mg. The is no hydrocodone tablet that has more than 10mg of the drug.
I imagine your prescription is for 5/500, or 5mg hydrocodone and 500mg APAP.
Try the weaning process if you can. Can you tell us more information, like your situation and what your narcotic history is? More info will help us give better guidance.