Detrimental effects of niacin/laropiprant on microvascular reactivity and red cell deformability in patients with elevated lipoprotein(a) levels

Several studies have found a beneficial effect of nicotinic acid on lipid profile, but there remains a limitation in the clinical use of nicotinic acid due to its side effects. In this study, 46 (F/M = 22/24, age = 58.74 ± 10.02 years) patients with Lp(a) ≥500 mg/L and with a previous arterial thrombotic event were treated with nicotinic acid/laropiprant (Tredaptive®). We found a significant reduction in the Lp(a) values at T1 (after 12 months), with a decrease of 32.3 % from baseline levels. At T1, 11 patients (23.9 %) showed Lp(a) levels to be <500 mg/L. PAT values were significantly decreased after treatment (2.13 ± 0.81 vs 1.74 ± 0.42, p = 0.001), showing a worsening of endothelial function in 27 (58.6 %) patients. A significantly higher number of patients had RHI <1.5 after the treatment [18 (39.1 %) vs 8 (17.4 %)]. Blood rheology worsened as ED was impaired (p < 0.0001) after 12 months, whereas WHV, plasma viscosity, and red cell aggregation did not show any significant differences in comparison to baseline. Patients with a worsening in microvascular reactivity in comparison to baseline showed a marked impairment in ED (0.3327 ± 0.037 vs 0.3091 ± 0.0351; p < 0.0001), while others showed only a mild, even though significant, reduction (0.3347 ± 0.0299 vs 0.3272 ± 0.0235; p = 0.044). In the light of the results of HPS2-THRIVE study, we may hypothesize that the addition of laropiprant to niacin might be responsible for these negative effects. In turn, these effects might explain, at least in part, the lack of a clinical net benefit of niacin/laropiprant in the trial.