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High maintenance doses of allopurinol, adverse drug reactions not significantly associated
No significant association was observed between high maintenance doses of allopurinol and adverse drug reactions, according to recent study results.
In identifying patients who had a definite or possible adverse drug reaction (ADR) to allopurinol, researchers retrospectively reviewed health records of 1,268 patients prescribed the drug from Jan. 1, 2004, to June 30, 2011. Logistic regression models were used to estimate associations of ADRs with maintenance doses of allopurinol at 1 to 1.5 times and more than 1.5 times the 1984 dosing suggestion of Hande et al and compared them with doses administered within the Hande suggested limits.
Patients were stratified based on Hande suggested dosing (within; n=481; mean age, 65.8 years; 28.9% women), between 1 to 1.5 times the Hande limit (above 1; n=515; mean age, 61.8 years; 15.7% women) or more than 1.5 times the Hande limit (above 1.5; n=272; mean age, 66.2 years; 31.2% women). Median allopurinol doses were 100 mg daily, 300 mg daily and 300 mg daily for the within, above 1, and above 1.5 groups, respectively.
Estimated weighted crude incidence rates for ADRs were 1.4% (95% CI, 0.3%-2.4%), 1.6% (95% CI, 0.5%-2.7%) and 2.6% (95% CI, 1%-5.2%), respectively, for the within, above 1 and above 1.5 groups (P=0.13 for above 1.5 vs. within).
Forty-eight patients experienced a definite ADR to allopurinol, including two who exhibited allopurinol hypersensitivity syndrome. Minor cutaneous reactions showed a slight increase when allopurinol maintenance doses exceeded 1.5 times the suggested Hande limit.
“The odds ratio of definite ADRs with maintenance doses of allopurinol 1 to 1.5 times and more than 1.5 times [the suggested dose limits] compared with doses within suggested limits were, respectively, 1.42 (95% CI, 0.66-3.04) and 2.04 (95% CI, 0.87-4.77),” the researchers reported.
“Cautious, gradual increases in allopurinol maintenance doses above the suggested limits of Hande et al are warranted … to achieve a serum uric acid level less than 6 mg/dL,” the researchers concluded.