Are there significant interaction effects between simvastatin-niacin and antioxidants? What does an interaction effect mean in the context of this trial? 

Cardiovascular Disease

A randomized trial examined the effects of lipid-modifying therapy (simvastatin plus niacin) and antioxidants (vitamins E and C, beta-carotene, and selenium) on cardiovascular protection in patients with clinical coronary disease, low HDL cholesterol, and normal LDL cholesterol [18]. A total of 160 patients were randomized into four groups: placebo lipid-lowering and placebo antioxidants, active lipid-lowering and placebo antioxidants, placebo lipid-lowering and active antioxidants, or active lipid-lowering and active antioxidants.

All participants had substantial stenoses (blockages) of the coronary arteries quantified by catheterization at baseline, and the primary endpoint was the percent change in a person€™s stenoses after 3 years of treatment, with a positive change indicating an increased amount of stenosis, as shown in Table 12.43. Because some patients did not complete the study, the primary endpoint was assessed in 146 participants.

Table 12.43: Mean changes (± sd ), per patient, in the percentage of stenosis by treatment group

 

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Simvastatin-niacin plus antioxidants (n = 40) 0.7 (+3.2) Antioxidants (n = 39) 1.8 (+4.2) Simvastatin-niacin (n = 33) -0.4 (+2.8) Placebo (n = 34) Mean change in stenosis 3.9 (+5.2) | (percentage of diameter)