Extended-release niacin (ERN) improves multiple lipid parameters but is underused owing to niacin-induced flushing (NIF). Laropiprant (LRPT) reduces NIF; however, its effects on chronic flushing (andgt;6 months) have not been studied. We examined whether after 20 weeks of treatment with ERN/LRPT, patients who continued ERN/LRPT would experience less NIF than patients who stopped LRPT and continued ERN alone. A total of 1,152 dyslipidemic patients were randomized 2:2:1 to group 1, ERN/LRPT 1 g/20 mg/day from 0 to 4 weeks and then ERN/LRPT 2 g/40 mg/day from 5 to 32 weeks; group 2, ERN/LRPT 1 g/20 mg/day from 0 to 4 weeks, ERN/LRPT 2 g/40 mg/day from 5 to 20 weeks, and then ERN 2 g/day without LRPT from 21 to 32 weeks; or group 3, placebo for the entire study. The end points included the number of days each week with a moderate or greater Global Flushing Severity Score (GFSS) andgt;= 4 (primary end point) and the percentage of patients with a maximum GFSS of andgt;= 4 (secondary end point) during the postwithdrawal period (weeks 21 to 32). ERN/LRPT produced significantly less NIF than ERN alone during the postwithdrawal period, as measured by the number of days each week with a GFSS of andgt;= 4 (p andlt; 0.001) and the percentage of patients with a maximum GFSS of andgt;= 4 (p andlt; 0.001; ERN/LRPT 19.6%; ERN 48.9%; placebo 9.2%). Compared with ERN alone, ERN/LRPT produced fewer drug-related adverse experiences during the postwithdrawal period. After 20 weeks of stable maintenance therapy, dyslipidemic patients treated continuously with ERN/LRPT experienced less NIF than did patients who had had LRPT withdrawn and had continued with ERN alone. In conclusion, the results of our study support the long-term efficacy of ERN/LRPT in reducing NIF symptoms.