Prognostic factors for colchicine prophylaxis-related adverse events when initiating allopurinol for gout: retrospective cohort study

Objectives: Colchicine is commonly used to prevent flares when starting urate-lowering therapy for gout. Patients with gout are frequently concurrently prescribed other medications (such as statins) that may interact with colchicine, increasing the risk of adverse events. The aim of this study was to describe potential prognostic factors for adverse events in patients prescribed colchicine when initiating allopurinol. Methods: We conducted a retrospective cohort study in linked UK Clinical Practice Research Datalink and Hospital Episode Statistics datasets. Adults initiating allopurinol for gout with colchicine (1 April 1997 to 30 November 2016) were included. Potential prognostic factors were defined, and the likelihood of adverse events, including diarrhoea, nausea or vomiting, myocardial infarction, neuropathy, myalgia, myopathy, rhabdomyolysis and bone marrow suppression, were estimated. Results: From 1 April 1997 to 30 November 2016, 13 945 people with gout initiated allopurinol with colchicine prophylaxis [mean age 63.9 (S.D. 14.7) years, 78.2% male]. One-quarter (26%, 95% CI 25%, 27%) were prescribed one or more potentially interacting medicines, most commonly statins (21%, 95% CI 20%, 22%). Statins were not associated with increased adverse events, although other drugs were associated with some adverse outcomes. Diarrhoea and myocardial infarction were associated with more comorbidities and more severe chronic kidney disease. Conclusion: People were given colchicine prophylaxis despite commonly having preexisting prescriptions for medications with potential to interact with colchicine. Adverse events were more common in people who had more comorbidities and certain potentially interacting medications. Our findings will provide much-needed information about prognostic factors for colchicine-related adverse events that can inform treatment decisions about prophylaxis when initiating allopurinol.