After using allopurinal 200mg for 3 years,is it possible to develop a "sensitivity" to it? My husband has been experiencing diarrhea, flu like symptoms, achy lower back bilaterally, loss of appetite, wt loss, metallic taste in mouth and now today blood in urine. This has been going on for 41/2 weeks. Stool samples have been neg. so far but still awaiting c diff results. Feels ok in am and then before lunch he starts to weaken. Also takes 2 Flomax 0.4 per tab. These pills are taken with his breakfast. Presently taking Flagyl for past 4 days for ? C diff. The diarrhea is less frequent but remains runny. Uses extra strength Immodium following the episodes of diarrhea.