International data suggest that suboptimal use of allopurinol is common. Allopurinol dose should be lower in renal impairment, but higher when gout is not controlled. The aim of the study was to examine trends in the usage of allopurinol in the Australian community.
Community dispensing data on the urate-lowering drugs allopurinol and probenecid were obtained from databases kept by Medicare Australia and the Drug Utilization Sub-Committee, for January 1992 to December 2005.
Allopurinol comprised 98.4% of all prescriptions for urate-lowering drugs dispensed during 2005. Most prescriptions were for allopurinol 300 mg, but there was a steady shift towards use of allopurinol 100 mg in all states and territories over the period of the study. There were marked variations in prescribing rates across the country. New South Wales had the highest rate of subsidized prescribing for allopurinol 300 mg (39.3 per 1000 population). Tasmania had the highest rate for allopurinol 100 mg (14.3 per 1000 population), which coincided with an educational programme to decrease allopurinol dose in patients with renal impairment. Prescribing rates in the Northern Territory were substantially lower than all other regions, at 10.8 and 3.3 prescriptions per 1000 population for allopurinol 300 and 100 mg, respectively.
The increased uptake of allopurinol 100 mg suggests greater adherence to dosing guidelines and that there is value in educational programmes to optimize drug usage. Variability in utilization rates across regions indicates the need for research on factors responsible. Precise understanding of dosing trends requires access to deidentified, individual dosing data.