Journal of Case Reports in Practice (JCRP) 2014; 2(1): 32-33 CASE REPORT Oral allopurinol desensitization SouSan Kolahi 1, Mahdi T ajeddini 1 and Mehran jalilzadeh Binazar 2 1 Connective Tissue Diseases Research Center, 2 Student Research Center, Tabriz University of Medical Sciences, Tabriz, Iran AbSTRACT Allopurinol, a xanthine oxidase inhibitor, is an effective urate-lowering drug. Unlike majority of patients tolerate allopurinol well, in 2% of patients receiving allopurinol, hypersensitivity reactions have been reported. In this case a 71-year-old woman with tophaceous gout since 10 years ago, presented to our rheumatology clinic. Because of occurring hypersensitivity reactions, allopurinol was discontinued and disease worsened despite administration of colchicine. She was admitted several times due to fare up of gout. Other forms of allopurinol are not available in Iran, so we decided to conduct an allopurinol desensitization protocol with tablets form. Side effects have not been reported yet. Key words: allopurinol, desensitization, gout InTROduCTIOn 1 Allopurinol, a xanthine oxidase inhibitor, is an effec- tive urate-lowering drug. Unlike majority of patients tolerate allopurinol well, in 2% of patients receiving allopurinol, hypersensitivity reactions have been re- ported. 1, 2 Since there are limited alternative treatments in gout, one of them is febuxostat, another xanthine oxidase inhibitor. 4 It is expensive and unavailable in Iran so we must desensitize hypersensitive patients to allopu- rinol. 3 About 78% of patients experience successful desensitization. 2 CASE REPORT A 71-year-old woman with tophaceous gout since 10 years ago presented to our rheumatology clin- ic. She had been treated with allopurinol for years, but because of occurring hypersensitivity reactions like facial rashes, swelling of lips and rashes in her wrists, drug use was stopped. Despite administration of colchicine, her disease worsened and she had re- nal dysfunction. She was admitted several times due to fare-up of gout. Multiple tophaceous deposits on both wrists, and left forth metatarsophalangeal and right second metatarsophalangeal joints, and arthritis in left elbow, and right frst metatarsophalangeal joint were revealed in physical examinations. Laboratory fndings are shown in Table 1. We decided to start on an allopurinol desensitization protocol. We dissolved 200 mg of allopurinol in 100 ml of normal saline (N/S) to make a concentration of 2mg/ml. Then we diluted 10 ml of this suspension in 100 ml of N/S to achieve a concentration of 200 μg / Correspondence: Mehran Jalilzadeh Binazar, Medical Student Student research center, Tabriz University of medical sciences, Tabriz, Iran E-mail: mehran.jalilzadeh@gmail.com ml (1 mg/5 ml). Oral desensitization was started ac- cording to Fam et al. Protocol. 2 She was desensitized to allopurinol successfully in 30 days. Next, 100 mg tablet of allopurinol was prescribed daily to the pa- tient for one year. After one year we increased dose of allopurinol to 150 mg daily. No side effects have been reported in follow up for two years and her renal function get normal and last serum uric acid was 5 mg/dL. dISCuSSIOn Allopurinol is the most widely prescribed urate-low- ering drug. 5 About 2 percent of patients using allo- purinol experience hypersensitivity reactions such as pruritic maculopapular rash, fever, facial swelling, or eosinophilia. Moreover, 0.4% of patients, with a mortality rate of 20%, experience more serious re- action such as erythema multiform, toxic epidermal necrolysis (TEN), acute hepatitis, interstitial nephri- tis, Stevens-Johnson syndrome (SJS), and vasculitis. 1, 2 The mechanism of hypersensitivity to allopurinol is not determined completely. 6 Some studies noted that there are at least three main patterns of hypersensi- tivity: 1) Nonspecifc skin rash, 2) IgE-mediated hy- persensitivity reactions, and 3) Cell-mediated hyper- sensitivity syndrome. 7, 8 Allopurinol hypersensitivity occurrence risk increases with aging and renal im- pairment. 9 In patients with history of vesiculobullous Table 1, Laboratory fndings of patient Blood measurements 24-hour urine measure- ments Uric acid: 10 mg/dL Creatinine: 1100 mg Hemoglobin: 10 g/dL Protein: 47 mg Creatinine: 1.3 mg/dL Uric acid: 272 mg Urea: 52 mg/dL Volume: 1600 cc 32