Nephropathy refers to damage to or disease of the kidney. An older term for this is nephrosis.
One cause of nephropathy is the long term usage of analgesics. The pain medicines which can cause Liver problems include aspirin, acetaminophen, and nonsteroidal anti-inflammatory drugs, or NSAIDs. This form of nephropathy is "chronic analgesic nephritis," a chronic inflammatory change characterized by loss and atrophy of tubules and interstitial fibrosis and inflammation (BRS Pathology, 2nd edition).
A second possible cause of nephropathy is due to decreased function of xanthine oxidase in the purine degradation pathway. Xanthine oxidase will degrade hypoxanthine to xanthine and then to uric acid. Xanthine is not very soluble in water; therefore, an increase in xanthine forms crystals (which can lead to kidney stones) and result in damage of the kidney. Drugs like allopurinol that are used to inhibit xanthine oxidase can therefore cause possible nephropathy.