Safety and compliance with once-daily niacin extended-release/lovastatin as initial therapy in the Impact of Medical Subspecialty on Patient Compliance to Treatment (IMPACT) study.

Niacin extended-release/lovastatin is a new combination product approved for treatment of primary hypercholesterolemia and mixed dyslipidemia. This open-labeled, multicenter study evaluated the safety of bedtime niacin extended-release/lovastatin when dosed as initial therapy and patient compliance to treatment in various clinical practice settings. A total of 4,499 patients with dyslipidemia requiring drug intervention was enrolled at 1,081 sites. Patients were treated with 1 tablet (500 mg of niacin extended-release/20 mg of lovastatin) once nightly for 4 weeks and then 2 tablets for 8 weeks. Patients also received dietary counseling, educational materials, and reminders to call a toll-free number that provided further education about dyslipidemia and niacin extended-release/lovastatin. Primary end points were study compliance, increases in liver transaminases to >3 times the upper limit of normal, and clinical myopathy. Final study status was available for 4,217 patients (94%). Compliance to niacin extended-release/lovastatin was 77%, with 3,245 patients completing the study. Patients in the southeast and those enrolled by endocrinologists had the lowest compliance and highest adverse event rates. Flushing was the most common adverse event, reported by 18% of patients and leading to discontinuation by 6%. Incidence of increased aspartate aminotransferase and/or alanine aminotransferase >3 times the upper limit of normal was <0.3%. An increase of creatine phosphokinase to >5 times the upper limit of normal occurred in 0.24% of patients, and no cases of drug-induced myopathy were observed. Niacin extended-release/lovastatin 1,000/40 mg, dosed as initial therapy, was associated with good compliance and safety and had very low incidences of increased liver and muscle enzymes.