Associated Factors for Allopurinol Induced Adverse Drug Reactions in Ratchaburi Hospital

Abstract

Background: Allopurinol is a well-known antihyperuricemic drug, but it occasionally induces adverse drug reactions. These were reported ranging from mild to severe adverse events such as allopurinol hypersensitivity syndrome (AHS), and might result in death.

Objective: To investigate risk factors for allopurinol induced adverse drug reactions in Ratchaburi Hospital, Thailand.

Material and Method: A matched case-control study was conducted using data from medical records of patients who had prescribed allopurinol in Ratchaburi Hospital between January 2007 and September 2015. Cases were all patients who had reported allopurinol induced adverse events to Ratchaburi drug-information-center. A control who had received allopurinol at least 1 year without adverse events was selected for each case matching on age and gender. Logistic regression was used to explore risk factors for adverse events.

Results: Two hundred and sixty patients (130 cases, 130 controls) were included with mean+S.D. age of 65.0+12.7 years. AHS was reported in 23 patients. The data showed that patients who developed adverse events had more chronic kidney disease (CKD) (80.8% vs 65.4%, p=0.005), more inappropriate indication of allopurinol prescription (53.1% vs 31.5%, p=0.001) and more high starting dose of allopurinol defining >1.5 mg per unit of GFR (mg/ml/minute) (90.8% vs 82.3%, p=0.046) than those who did not. In multivariate analysis, CKD and inappropriate indication of prescription were still the independent risk factors for adverse events with OR (95%CI) 2.43 (1.17, 5.04) and 3.0 (1.36,6.56), respectively. In contrast, co-medication and history of previous allopurinol users did not significantly associate with adverse events.

Conclusion: This finding indicated that CKD and inappropriate indication of allopurinol prescription were the risks for developing allopurinol induced adverse drug reactions.