• Primary Endpoint: The change in serum phosphorus after 8 weeks of niacinamide versus placebo.
  

• Secondary endpoints: To assess the effects of niacinamide on calcium-phosphorus product, biointact parathyroid hormone levels (biPTH), and lipid profiles after 8 weeks of therapy.
  

This is a prospective, randomized, double-blind, placebo-controlled crossover study comparing niacinamide versus placebo in the reduction of serum phosphorus in hemodialysis patients. A determination of baseline laboratory values (serum phosphorus, calcium, albumin, biPTH, uric acid, complete blood count (CBC), and an NMR lipid panel) will precede the administration of the study drugs. The study will span a period of 21 weeks during which phosphorus levels will be checked on a weekly basis. Phosphorus binder dose will remain unchanged unless for safety reasons. For the first 8 weeks of treatment, patients will be randomized to either placebo or niacinamide. Both medications will be administered with a starting dose of one capsule twice per day (BID). Niacinamide and placebo will be formulated in 250 mg capsules. Placebo will be packaged to resemble the study drug in all physical attributes. The dose of niacinamide or placebo will be increased to 500 mg (2 capsules) BID at week 3 and 750 mg (3 capsules) BID at week 5. If hypophosphatemia (< 3.5 mg/dl) is present, then titration will not occur and the previous dose will be continued. However, titration will resume in subsequent weeks if the serum phosphorus is greater than 3.5 mg/dl. After 8 weeks, patients will undergo a 2 week washout period, then crossover from treatment arm to placebo, or vice versa, at week 11.

At the beginning of week 11, patients will cross over to the other treatment arm (either placebo or niacinamide) at one capsule (250 mg) twice per day. Subsequent titration will occur at week 13 and week 15. The treatment phase will be completed at the end of week 18. A set of labs will be drawn at the start of week 19, followed by a two week washout period.