Hyperphosphatemia is common in the peritoneal dialysis population. Current strategies are insufficient to optimize phosphorus control. Animal studies have shown niacinamide, a form of vitamin B, to reduce phosphate uptake by the rat small intestine. Our trial investigates the use of niacinamide, in addition to standard phosphorus lowering strategies, to reduce plasma phosphorus levels in peritoneal dialysis patients versus placebo.

This is a prospective, randomized, double-blind, placebo-controlled 8-week clinical trial to evaluate the efficacy of niacinamide versus placebo to reduce plasma phosphorus levels in peritoneal dialysis patients. Patients on a stable regimen of phosphate binders with plasma phosphorus levels > 4.9 mg/dL are eligible for enrollment and randomization. The study will span 8 weeks of active medication treatment. The primary end-point will be absolute change in plasma phosphorus levels. Sixteen patients (8 randomized to each treatment arm) are needed to detect a 1.5 mg/dL difference assuming a standard deviation of 1 and powered at 80% (alpha 0.05). Placebo will be packaged to resemble the study drug in all physical attributes. The starting dose of niacinamide will be 250 mg twice daily to be titrated to 500 mg twice daily at the end of week 2 with a final titration to 750 mg twice daily at the end of week 4. Secondary end-points will include absolute change in the calcium-phosphorus product, intact parathyroid hormone, hemoglobin, platelet count, total cholesterol, HDL cholesterol, and percentage change in plasma phosphorus.

Inclusion Criteria:

• Age > 18 years
• Capable of giving informed consent
• Duration of peritoneal dialysis > 3 months
• Dose of phosphate binder(s) stable over previous 2 week period
• Plasma phosphours > 4.9 mg/dL based on most recent laboratory data within 1 month of enrollment

Exclusion Criteria:

• Pregnancy
• Known liver disease
• Active peptic ulcer disease
• Treatment with carbamazepine
• Intolerance to niacinamide or niacin
• Current medication regimen including niacin or niacinamide > 100 mg daily
• Planned or expected surgical procedure in the next 4 months
• Patients in nursing home or extended care facilities where administration of the study drug may not be appropriately given