The Incidence of Hyponatremia with Two Commonly Prescribed Purgatives for Colonoscopy - Polyethylene Glycol 3350 with Sports Drink (PEG-SD) Compared to Polyethylene Glycol with Electrolyte Solution (PEG-ELS): ACG/AstraZeneca Fellow Award

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Purpose: Polyethylene glycol 3350 combined with a sports drink (PEG-SD) is a hypo-osmotic purgative commonly used for colonoscopy (“colon”). Little safety data are available for this non-FDA approved purgative. The purpose was to evaluate the effect of PEG-SD on serum electrolytes. Methods: Single center, prospective, randomized, investigator-blind comparison of PEG-ELS to PEG-SD for outpt colon. SD = Lemon-Lime Gatorade®; PEG-ELS = MoviPrep®. PEG-ELS regimen was 1L + 500cc clears at 6 pm and 4 hrs before colon. PEG-SD regimen was a single 10 mg dose of bisacodyl at 3 pm, and 1L SD with 119 g PEG 3350 at 6 pm and 4 hrs before colon. Diet was a low residue breakfast day prior followed by clears up to 2.5 hrs before colon. Baseline labs were obtained 2-5 days prior to colon, and repeated immediately before and after colon. Pts completed side effect (SE) questionnaires prior to colon. Changes in levels of electrolytes and eGFR were computed as the difference between the lowest value on the day of colonoscopy and baseline. Preparation was graded as adequate (good or excellent) or inadequate (fair, poor). Primary endpoint was development of hyponatremia (Na <135 mmol/L) day of colon. The study had 80% power to detect a 3-fold difference in incidence of hyponatremia between the two groups (5% vs 14%). Results: 389 pts were randomized between 7/2010 and 6/2012, and 25 were excluded (13 for hyponatremia at baseline). 364 analyzed pts ingested purgative and had baseline and day of colon labs (180 PEG-SD, 184 PEG-ELS). The groups were well matched except for a higher fraction of women and Blacks in PEG-ELS group. 7 pts (3.9%) in PEG-SD and 4 pts (2.2%) in PEG-ELS developed hyponatremia (OR = 0.55, exact 95% CI: 0.12 to 2.21, p = 0.376). For these 11 pts, the mean Na change was -5.3, SD = 2.7, with no instances of Na <131 mmol/L. Changes in electrolytes from baseline were small but significantly greater with PEG-SD for Na, potassium (K), and chloride (Cl) (PEG-SD vs PEG-ELS: ΔNa -0.7 vs 0.5, p = 0.001; ΔK -0.2 vs -0.1, p = 0.022; ΔCl -0.9 vs 0.5, p = 0.001). Neither group had a significant change in renal function. There was no significant difference in SEs or prep completion between the 2 groups. 1 pt in PEG-SD group had an acute MI after completing AM dose, and 1 pt in PEG-ELS group had an asthma flare in AM after completing PM dose. Both occurred prior to colon. Preparation adequacy was similar between the study groups (PEG-SD = 87% vs PEG-ELS = 86%), but there were more excellent preparations with PEG-ELS (52% vs 30%). Conclusion: Hyponatremia is rare and not significantly increased with PEG-SD as compared to PEG-ELS. Greater, but very modest, electrolyte changes occur with PEG-SD. Preparation completion, quality, and SEs are similar with both purgatives. Disclosure: Dr. Kastenberg - Salix Pharmaceuticals: consultant, research support This research was supported by an industry grant. Salix Pharmaceuticals provided financial support/research grant.