Different companies make generics of the same medicines. For generic medications there is some leeway. In other words, the generic medication produced may have slightly more or slightly less of the active ingredient in it (so you may be taking something like 5.5 mg or 4.5 mg, depending on the batch & the company) than does the brand name medicine (which is highly regulated & will have exactly 5 mg). Also, different generics contain different inactive ingredients. The combination of the difference in inactive ingredients & the difference in actual oxycodone present in the two different generics probably accounts for your different response to the same medication.
Perhaps you can explain the problem to your pharmacist & ask to be given pills from the manufacturer who's pills work better for you (if they have them in stock, the brands they carry may vary from time to time due to price, availability, etc). Or you could ask your doctor to write a prescript
ion requiring you to get the brand name medication (although this is more expensive & may not be covered by your insurance since there is a generic form available). Like you said, another possibility is tolerance, but due to the sudden nature & the correspondence with the new meds, I'd be more suspicious of the medication itself.
I hope this all makes sense, it's pretty late & my eyes (and brain) aren't working so well.
Post Edited (skeye) : 2/4/2010 10:24:46 PM (GMT-7)