Common generic Zyloprim side effects include diarrhea, nausea, rash and itching, and drowsiness. This medicine should be discontinued immediately at the first appearance of rash, painful urination, blood in the urine, eye irritation, or swelling of the mouth or lips, because these can be a signs of an impending severe allergic reaction that can be fatal. Patients with a prior severe reaction to the drug should not buy Zyloprim. This drug can cause a flare-up of gouty arthritis during initial therapy. Rarely, cheap Zyloprim online can cause nerve, kidney, and bone marrow damage. This med can cause a serious allergic liver toxicity that can be fatal. Loss of appetite and itching can be signs of liver toxicity. The risk of this reaction is higher in patients with kidney impairment.