Increased risk of severe hyponatremia with miralax-Gatorade vs standard bowel preparation

Purpose: A hyperosmolar formulation of Miralax-Gatorade (238g of PEG-3350 in 64oz of Gatorade) has gained wide acceptance for bowel prep prior to colonoscopy. This prep is not FDA-approved nor has its safety been proven in clinical trials. We have previously reported a case series of patients with severe hyponatremia (serum sodium < 130 mEq/l) associated with the miralax-gatorade (M-G) bowel preparation. In this study, we report the incidence of severe hyponatremia with the M-G bowel prep vs FDA-approved PEG bowel preps. Methods: In an IRB-approved, retrospective endoscopic database study, we identified individuals who presented to the emergency department (ED) at our institution 24 or fewer hours prior to scheduled colonoscopy. Electronic medical records were then searched to identify individuals with documented severe hyponatremia. Additional data about indication for colonoscopy, age, gender, concurrent chronic medical disorders, concurrent medications, lowest recorded serum sodium, need for hospitalization, pre-hospitalization symptoms, and response to therapy were also recorded. Data analysis utilized Fisher's Exact Test to compare the two groups. Results: Among 8413 colonoscopies performed at two sites in 2009, 0.13% (3/2304) of M-G patients and 0.032% (2/6109) of FDA-approved PEG bowel prep patients suffered severe hyponatremia: odds ratio = 3.98; 95% confidence intervals 0.66-23.8; p = 0.10. The two patients in the FDA-approved PEG bowel prep group had severe gastroparesis/DM and htn/renal insufficiency, respectively. Among the 3 patients in the M-G group, one patient suffered from htn and used a diuretic, while the other two patients had no concurrent medical disorders/medications that would be associated with electrolyte abnormalities. All patients presented with a combination of N/V, pre-syncope, mental status changes, or abdominal pain. Among 8,544 colonoscopies performed in 2010, no patients met inclusion criteria for this analysis, although one M-G patient presented with severe hyponatremia within 24 hours after her colonoscopy. Conclusion: Severe symptomatic hyponatremia may be associated with hyperosmolar Miralax-Gatorade bowel preps. Our study demonstrates a non-significant trend for an increased risk with M-G preps. Current data does not warrant discontinuing use of this prep, but larger studies are needed to more precisely quantify the risk of this infrequent complication of bowel preparation.