Degree of serum LDL cholesterol reduction by simvastatin and ezetimibe is dependent on baseline LDL cholesterol concentration but not on baseline values and changes in cholesterol synthesis and absorption parameters.

Objective: We questioned whether the baseline status of low-density lipoprotein cholesterol (LDL-C), cholesterol synthesis and absorption, and the changes in these parameters determine the change in serum LDL-C under statin or ezetimibe treatment or under combination treatment.
Materials and Methods: 37 mildly hypercholesterolemic healthy male subjects were studied under placebo, simvastatin (20 mg/d), ezetimibe (10 mg/d), and combination treatment. We correlated the change of LDL-C (ΔLDL-C) under treatment with the placebo end values of LDL-C (baseline), whole-body cholesterol synthesis, and hepatic cholesterol synthesis (serum lathosterol to cholesterol ratio) as well as fractional absorption rate (FAR) of cholesterol and serum campesterol to cholesterol ratio. The change in serum LDL-C was also correlated with the changes in synthesis and absorption parameters.
Results: ΔLDL-C was highly negatively related to baseline LDL-C under ezetimibe (p < 0.0001), simvastatin (p < 0.0001), and combination treatment (p < 0.0001). Under combination treatment, LDL-C lowering appears possible from baseline values of 10 mg/dL upwards, while ΔLDL-C was independent of the baseline value (-50 to -60%). ΔLDL-C was positively associated with placebo FAR under ezetimibe (p = 0.0106) and combination treatment (p = 0.0457). No associations were found between ΔLDL-C and baseline values for synthesis nor between ΔLDL-C and changes in synthesis and absorption surrogate markers.
Conclusion: Under ezetimibe, simvastatin, and combination treatment, ΔLDL-C is predominantly dependent on the baseline LDL-C concentration. We hypothesize that the concentration gradient between serum LDL-C and hepatic cellular cholesterol determines the efficiency of serum LDL-C lowering. Combination treatment is the preferred treatment.