In order to study the proper use of urate-lowering drugs, we searched and analyzed a recently established database of 151, 804 community pharmacy records for the one-year period ending in August 1997. A total of 5, 312 prescriptions for typical urate-lowering drugs, allopurinol and benzbromarone, were searched. The number of male patients was found to be approximately 6.5 times that of females (578 and 89, respectively). The average age was 59.8 years (range 15 to 90 years). Of the 5, 312 prescriptions examined 81.4% were for allopurinol, 17.1% for benzbromarone and 1.5% for both. The number of prescriptions for allopurinol was approximately 4.5 times greater than that for benzbromarone. Hyperuricemia is classified into three types. The first type, includes patients who under-excrete uric acid, occurs in approximately 55% of patients. Uricosuric drugs such as benzbromarone are considered to be the drugs of choice. The second type, consists of over-producers of uric acid, occurs in approximately 10% of patients. The third type, comprising a mixed category, accounts for the remaining 30%. Allopurinol is recommended for the latter group of both under-excreters and over-producers. Given this classification, benzbromarone should thus be prescribed on a relatively frequent basis.
The average number of drugs per prescription was 5.9 (range 1 to 25 drugs) thus indicating that patients with hyperuricemia tend to be prescribed multiple-drug regimens. From the analysis of concomitant drugs, it was found that the most frequently prescribed drug was furosemide (22.4%), followed by nifedipine sustained-release preparations (15.7%), pravastatin sodium (11.7%) and aspirin diaulminate for children (10.7%). The most frequently prescribed drug group was vasodilators (60.2%) including calcium antagonists and nitrates, followed by peptic ulcer agents (44.4%), anti-arteriosclerotic agents (27.1%), anticoagulants (25.1%), diuretics (24.2%) and ACE inhibitors (20.7%). These finding suggest that patients with hyperuricamia tend to have multiple complications such as hypertension, hypercholesterolemia, and ischemic cardiopathies.
Inappropriate drug use and combinations are as follows: Alkalinizing agents, which prevent urate stone formation and are recommended for hyperuricemia, appear to be under-utilized (only 11.8%). Diuretics, trichlormethiazide (2.5%) and furosemide (22.4%) commonly cause hyperuricemia and thus should be avoided. When allopurinol and captopril are administered concomitantly (2.9%), a dangerous hypersensitivity reaction can also sometimes occur.
These results indicate that doctors and pharmacists need to obtain a greater awareness of inappropriate drug use and dangerous drug combinations.
