Efficacy and Safety of Extended Release (ER) Niacin/Laropiprant When Added to Ongoing Lipid-Modifying Therapy in Patients With High Cholesterol or Abnormal Lipid Levels (MK-0524A-133)

Inclusion Criteria: * Has a history of primary hypercholesterolemia or mixed dyslipidemia. * Must meet one of the risk categories (very high, high or moderate and corresponding LDL-C criteria at Visit 2. * Has TG levels \<500 mg/dL (\<5.65 mmol/L). * Has been on a stable dose of one of the following lipid-modifying therapies (LMTs)for at least 6 weeks prior to Visit 1, and agrees to remain on the same type and dose of LMT for the duration of the study: * Monotherapy: any statin * Combination Therapy: ezetimibe/simvastatin in the same tablet * Co-administration Therapy: any statin co-administered with ezetimibe * Is male or female and ≥18 years of age on day of signing informed consent. * A female must meet ONE of the following: * Of reproductive potential and agrees to remain abstinent or use (or have their partner use) 2 acceptable methods of birth control for the study duration. * Not of reproductive potential is eligible without requiring the use of contraception. Definition of "not of reproductive potential": one who has either of the following: * reached natural menopause, defined as: 6 months of spontaneous amenorrhea with serum FSH levels (at Visit 1) in the postmenopausal range (per central lab) or 12 months of spontaneous amenorrhea.Spontaneous amenorrhea does not include cases for which there is an underlying disease that causes amenorrhea (e.g., anorexia nervosa). * 6 weeks post surgical hysterectomy, or bilateral oophorectomy with or without …