OBJECTIVE: A residue-free sodium phosphate tablet (RF-NaP) was formulated that lacks microcrystalline cellulose, which can appear as a whitish residue in the colon. A multicenter, randomized, investigator-blinded study was conducted to compare the colon-cleansing efficacy of 40 or 32 tablets of RF-NaP with the marketed 40-tablet NaP treatment regimen. METHODS: Eight hundred sixteen patients were randomized prior to colonoscopy to receive either 40 tablets (60 g) of NaP or RF-NaP or 32 tablets (48 g) of RF-NaP. Colon cleansing was assessed using a 4-point scale based on retained "colonic contents." The primary end point was overall colon-cleansing response rate to treatment (score of excellent/good) versus nonresponse (fair/inadequate). RESULTS: Seven hundred four patients were included in the efficacy analysis. The overall colon-cleansing response rates were comparable among treatment arms (94.5%, 97.0%, and 95.3% for NaP, RF-NaP 40, and RF-NaP 32 tablets, respectively). Ascending colon-cleansing response rates for RF-NaP 40 (95.7%) and 32 tablets (93.6%) were significantly better than for NaP tablets (88.5%, p < 0.03 for both). Patients treated with RF-NaP 32 tablets experienced less pronounced changes in electrolyte levels and fewer adverse events (138/239, 58%) compared with patients receiving NaP (161/238, 68%, p = 0.07) and RF-NaP 40 tablets (156/236, 66%, p = 0.03). The most common adverse events reported were abdominal distention, nausea, abdominal pain, and vomiting. CONCLUSIONS: Based on the safety, efficacy, and patient preferences, the 32-tablet RF-NaP regimen was superior to the 40-tablet RF-NaP and NaP regimen for colon cleansing prior to colonoscopy.
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