The use of Ribavirin to treat chronic hepatitis C in patients receiving azathioprine has been reported to induce severe pancytopenia and may increase the risk of azathioprine-related myelotoxicity. Inosine monophosphate dehydrogenase (IMDH) is required for one of the metabolic pathways of azathioprine.
There are several common underlying causes of kidney disease. 1  In older cats Interstitial Nephritis is most frequently seen. 2  Polycystic Kidney Disease (PKD) is a very common problem in Persian cats - 20-30% of them can be affected. 3  Tumours are occasionally seen in middle-aged and older cats.
Toxins caused by the kidney disease, including excess stomach acid, are one of the most likely culprits in cats with creatinine over 3 mg/dl (USA) or 265 mmol/L (international), though they can also be a problem in cats with lower creatinine levels. There are a number of treatments that can help.