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Background: The bowel purgative Visicol contains microcrystalline cellulose (MCC) residue, which may impair full visibility during a colonoscopy. An MCC residue-free sodium phosphate (RF-NaP; OsmoPrep) tablet was developed., Objective: To investigate appropriate RF-NaP dosing., Design: Phase 2, randomized, investigator-blinded study., Setting: Six research centers in the United States., Patients and Interventions: Patients undergoing a colonoscopy received Visicol (n = 34) or 1 of 6 RF-NaP regimens administered as either split (S) dosing (the evening before and the day of colonoscopy) or evening-only (E) dosing. Dosing regimens for RF-NaP were 40 tablets S, 3 every 15 minutes (n = 33); 40 tablets S, 4 every 15 minutes (n = 34); 32 tablets E, 4 every 15 minutes (n = 34); 32 tablets S, 4 every 15 minutes (n = 36); 28 tablets E, 4 every 15 minutes (n = 34); 28 tablets S, 4 every 15 minutes (n = 34). Visicol was administered as 40 tablets S, 3 every 15 minutes., Main Outcome Measure: Overall colon cleansing (OCC) was assessed by a physician questionnaire (4-point scale, based on colonic contents). An OCC rating of "excellent" or "good" was considered a response. Safety measures were also monitored., Results: Split dosing with RF-NaP was associated with high OCC and achieved response rates of 90%, 97%, and 100% for 28, 32, and 40 tablets, respectively, compared with 86% for Visicol. In addition, RF-NaP evening-only regimen response rates were 90% (32 tablets) and 72% (28 tablets). Transient shifts in electrolyte levels were reduced, and GI adverse events were less common with lower RF-NaP dose regimens., Conclusions: Administration of RF-NaP retains the benefits of a tablet purgative but eliminates MCC issues. Split dosing and 32-tablet evening-only dosing of RF-NaP tablets were efficacious and well tolerated, and split dosing of RF-NaP tablets is recommended.

Background: The tablet formulation of sodium phosphate (NaP) is a prescription osmotic purgative that has been marketed since 2001. The use of NaP tablets in patients with constipation has not been studied previously., Objective: This study assessed the tolerability and efficacy of 28 days of therapy with NaP tablets (1.5 g NaP/tablet) in patients with chronic constipation., Methods: Adults with functional constipation or constipation-predominant irritable bowel syndrome and Z-3 spontaneous bowel movements (BMs) during the 7-day screening/baseline period were eligible for this open-label, dose-ranging study. Patients were randomized to receive starting doses of 4 NaP tablets (group A) or 8 NaP tablets (group B) each morning for 28 days. After a minimum of 48 hours, the NaP dose could be titrated upward (in the case of no BM or no relief of symptoms) or downward (in the case of a predefined excess laxative response) by 2 tablets/d to a minimum of 2 tablets/d or a maximum of 12 tablets/d. Patients kept a diary of their BMs and gastrointestinal symptoms. A serum chemistry panel was obtained weekly. The primary end points were the constipation response (based on the change from baseline in weekly number of BMs) and the global sense response (based on daily scores for the patient's overall sense of change in their bowel problems)., Results: At randomization, there were 18 patients in group A and 25 in group B. Of these, 40 patients (16 group A, 24 group B) had > or 7 days of diary information while taking study treatment and were evaluable for efficacy. The constipation response rate was 100% in group A and 95.8% in group B, and the respective global sense response rates were 68.8% and 79.2%. Four patients in group B withdrew due to adverse events, none of which were serious. Five patients had occasional hypokalemia that required no treatment. Changes from baseline in serum concentrations of calcium, inorganic phosphorus, and potassium were not clinically significant and did not require treatment., Conclusions: In this small study, NaP tablets taken daily were generally well tolerated (particularly in the low-dose group) and produced prompt relief of constipation--generally within the first week of treatment--that was sustained over the 28-day treatment period. A reasonable starting dose appears to be 2 to 4 tablets (3-6 g NaP) daily.