Niacin is a useful lipid-modifying drug because it (1) decreases low-density lipoprotein (LDL) cholesterol, total cholesterol, triglycerides, and lipoprotein(a), and (2) raises high-density lipoprotein (HDL) cholesterol. Its use tends to be limited by side effects and inconvenient dosing regimens. The availability of an extended-release preparation (Niaspan-which has safety and efficacy similar to immediate-release niacin but which can be given once a day) provides an opportunity to increase the use of this effective lipid-modifying agent. To study the safety and efficacy of escalating doses of extended-release niacin, hyperlipidemic patients were randomly assigned to placebo or Niaspan. A forced dose-titration was done with the dosage increasing by 500 mg every 4 weeks to a maximum of 3,000 mg/day. Niaspan showed dose-related changes in total, LDL, and HDL cholesterol levels, triglycerides, cholesterol/HDL ratio, and lipoprotein(a). At a dosage of 2,000 mg/day, total cholesterol decreased by 12.1%, LDL cholesterol by 16.7%, triglycerides by 34.5%, and lipoprotein(a) by 23.6%; HDL cholesterol increased by 25.8%. Flushing was the most commonly reported side effect; flushing episodes tended to decrease with time despite an increasing dose of niacin. Of the reported side effects, only pruritus and rash were significantly different between the 2 groups. Aspartate aminotransferase, lactate dehydrogenase, and uric acid increased in a dose-dependent fashion, but fasting blood sugar increased by about 5% across most dosages. Two subjects had aspartate aminotransferase levels greater than twice the upper limit of normal, but there were no subjects in whom transaminases increased to 3 times the upper limit of normal. Women tended to have a greater LDL cholesterol response to the medication and also experienced more side effects, especially at higher dosages. Thus, the use of lower dosages of niacin may be desirable in women. The results of this dose-escalation study show beneficial effects of Niaspan on the entire lipid profile. At the maximum recommended dosage of 2,000 mg/day, all lipid and lipoprotein levels changed in desirable directions. Side effects (other than flushing) and blood chemistries were comparable to those seen with immediate-release niacin.