Table 2

Crude incidence rate of incident hypersensitivity reactions with allopurinol, febuxostat or colchicine exposure†

Person-days of follow-up#CasesIncidence rate
/100 000 person-days
Incidence rate
/1000 person-years
Allopurinol1 1167 7917316.523.91
Febuxostat610 115518.430.53
Colchicine2 400 4831697.025.71
Allopurinol+colchicine946 440717.527.40
Allopurinol+febuxostat34 78938.631.50
Febuxostat+colchicine70 7191115.656.81
Allopurinol+febuxostat+colchicine8191224.489.18
Allopurinol, days
 ≤30790 54616020.273.92
 >30 to ≤60744 4337510.136.80
 >60–90573 745427.326.74
 >90–120524 781479.032.71
 >1209 104 0434535.018.17
Febuxostat, days
 ≤3054 187916.660.70
 >30 to ≤6057 372813.950.93
 >60–9045 61624.416.01
 >90–12043 81649.133.34
 >120489 770398.029.08
Colchicine, days
 ≤30555 612539.534.84
 >30 to ≤60340 207257.326.84
 >60–90156 794138.330.28
 >90–120134 690107.427.12
 >1201 622 913986.022.06
Allopurinol starting dose, mg/day
 <2005 695 4153426.021.93
 200–2992 110 1081195.620.60
 ≥3003 932 0253168.029.35
Febuxostat starting dose, mg/day
 40565 682539.434.22
 801 225 07990.72.68
Colchicine starting dose, mg/day
 <0.6380 142184.717.29
 0.6 to <11 090 327837.627.80
 1 to <21 151 515907.828.55
 ≥2188 14284.315.53
Allopurinol average dose, mg/day*
 <2005 884 0093536.021.91
 200–2992 216 8641275.720.92
 ≥3004 056 3353278.129.44
Febuxostat average dose, mg/day*
 40593 913579.635.05
 80129 898107.728.12
Colchicine average dose, mg/day*
 <0.6477 550194.014.53
 0.6 to <11 348 9651118.230.05
 1 to <21 382 3301087.828.54
 ≥2216 898156.925.26
  • *Totals over all dose combinations exceeds the total for the drug, as people could contribute to multiple categories.

  • †Drug exposure up to 30 days after last day of medication fill/refill; baseline period was 365 days, that is, each new exposure was defined as no previous exposure in the baseline.