All pain medications affect the liver to some degree. Looking at the Drug Information Handbook, Ultram (tramadol) has liver failure as a side effect, occuring in <1% of cases.
Darvon has a side effect of increasing the liver enzymes, with a frequency that is non-defined.
There are no head-to-head studies comparing the liver effects of these two medications that I am aware of.
As for other pain medication considerations, Vioxx and Celebrex (both COX-2 inhibitors) has a hepatitis rate of <2%.
To my knowledge, there are no pain medications that are 100% safe for the liver. Discussion of all the above medications should be done with your personal physician.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Thanks,
Kevin, M.D.