Increased risk of lymphomas & other malignancies. Immunosuppressed patients. Pure red cell aplasia (PRCA). Monitor complete blood & absolute neutrophil count. Increased incidence of digestive system adverse events. Avoid use of live attenuated vaccines & doses >1 g bd to renal transplant patients. Avoid exposure to sunlight & UV light. Switching combination therapy from regimens containing immunosuppressants. Severe renal impairment. Elderly.