Table 4

 Evidence of safety: relative risk and 95% confidence intervals

ComparisonAdverse eventsRR* (95% CI)EvidenceReference
*RR: relative risk between treatment group and control group: RR = 1, no difference; RR >1, more risk with treatment; RR <1, more risk with control.
AHS, allopurinol hypersensitivity syndrome; CI, confidence interval; CT, controlled trial; FPE, fixed pigmented drug eruption; GI, gastrointestinal; LCV, leucocytoclastic vasculitis; RCT, randomised controlled trial.
Colchicine v placeboNausea, vomiting or diarrhoea4.20 (1.95 to 9.03)RCT, 48 hours17
Diarrhoea8.38 (1.14 to 61.38)RCT, 3 months22
Colchicine+probenecid v probenecidAny1.69 (0.95 to 3.00)RCT, 6 months23
GI1.69 (0.95 to 3.00)RCT, 6 months23
Diarrhoea1.35 (0.60 to 3.04)RCT, 6 months23
Nausea/vomiting1.98 (0.85 to 4.60)RCT, 6 months23
Azapropazone v allopurinolAcute duodenal ulcer2.20 (0.09 to 53.59)CT, 6 months24
Nausea/dyspepsia51.68 (3.21 to 833.18)CT, 6 months24
Diarrhoea/abdominal pain2.20 (0.23 to 20.85)CT, 6 months24
Headache/dizziness1.10 (0.19 to 6.47)CT, 6 months24
Allopurinol:
    Allopurinol v placeboCreatinine clearanceReduced to p>0.02RCT, 2.5 years13
    Adjusted dose v unadjusted doseRash, AHS, FPE, LCV1.96 (0.34 to 11.92)Cohort study,44
    Exposure v non-exposureCataract1.82 (1.18 to 2.80)Case–control45