Niacin lowers LDL cholesterol and raises HDL cholesterol. The THRIVE trial randomly assigned more than 25,000 patients with vascular disease to receive either extended-release niacin with laropiprant or matching placebo. 245 sites were located in the UK, Scandinavia and China. During a median follow-up of 3.9 years, participants randomly assigned to niacin had lower LDL cholesterol and higher HDL cholesterol compared to matching placebo in patients whose LDL cholesterol had been standardized through prior statin therapy.
The primary outcome measure for the trial was time to the time to the first major vascular event (nonfatal myocardial infarction, death from coronary causes, stroke, or arterial revascularization). Assignment to niacin compared to placebo had no effect on the incidence of major vascular events (13.2% and 13.7% of participants with an event, respectively; rate ratio, 0.96; 95% confidence interval [CI], 0.90 to 1.03; P = 0.29).
By contrast, significant differences were seen in the incidence of adverse events in the niacin group. These included increased incidences of disturbances in diabetes control that were considered to be serious (absolute excess as compared with placebo, 3.7 percentage points; P<0.001) and with an increased incidence of diabetes diagnoses (absolute excess, 1.3 percentage points; P<0.001), as well as increases in serious adverse events associated with the gastrointestinal system (absolute excess, 1.0 percentage point; P<0.001), musculoskeletal system (absolute excess, 0.7 percentage points; P<0.001), skin (absolute excess, 0.3 percentage points; P = 0.003), and unexpectedly, infection (absolute excess, 1.4 percentage points; P<0.001) and bleeding (absolute excess, 0.7 percentage points; P<0.001).
Taken together, the results of the THRIVE clearly showed that niacin had no apparent benefit and may be associated with significant risk. What is perhaps most striking is the clarity of the result demonstrating the value of undertaking a large-simple randomised trial in more than 25,000 participants. If the trial had been conducted on a smaller sample, perhaps, 5,000 participants, which would still have been a moderately sized study, such a clear result in terms of the lack of effect on vascular events would not have been obtained. The likely outcome would have been calls for further trials of treatment with niacin in this high-risk population. Fortunately, the size of the THRIVE trial has meant that further trials of treatment with niacin are unnecessary.
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