Allopurinol can be used for primary and secondary hyperuricemia by inhibiting uric acid production, and also for the treatment of patients with recurrent or chronic gout. Patients may experience the following side effects, including rash, pruritic papules or urticaria, which must be discontinued if the rash is widespread and persistent, if symptomatic treatment is ineffective, and if there is a tendency for it to worsen. Allopurinol can also cause gastrointestinal reactions such as diarrhea, nausea, vomiting and abdominal pain. Allopurinol can also cause leukopenia, or thrombocytopenia, anemia, and bone marrow suppression, and should be considered for discontinuation if these conditions occur. Allopurinol may also cause alopecia, fever, lymph node enlargement, hepatotoxicity, interstitial nephritis, and allergic vasculitis. There have been reports of sudden death during administration of allopurinol, as well as exfoliative dermatitis, toxic epidermolysis bullosa, severe erythema multiforme rash, drug hypersensitivity syndrome, hepatic impairment, and renal impairment, so it is important to monitor the drug and seek medical advice if there are any abnormalities.