Hyponatremia and sodium picosulfate bowel preparations in older adults

Am J Gastroenterol. 2014 May;109(5):686-94. doi: 10.1038/ajg.2014.20. Epub 2014 Mar 4.


Objectives: Bowel preparations are commonly prescribed drugs. Case reports and our clinical experience suggest that sodium picosulfate bowel preparations can precipitate severe hyponatremia in some older adults. At present, this risk is poorly quantified. We investigated the association between sodium picosulfate use and the risk of hyponatremia in older adults.

Methods: We conducted a population-based retrospective cohort study using six linked administrative databases in Ontario, Canada. All Ontario residents over the age of 65 years who filled an outpatient bowel preparation prescription before colonoscopy were eligible. We enrolled new users of either sodium picosulfate (n=99,237) or polyethylene glycol (n=48,595). The primary outcome was hospitalization with hyponatremia within 30 days of the bowel preparation assessed by database codes. The secondary outcomes were hospitalization with urgent head computed tomography (CT) (a proxy for acute central nervous system disturbance) and all-cause mortality.

Results: The baseline characteristics of the two groups, including patient demographics, comorbid conditions, and concomitant medications, were nearly identical. Compared with polyethylene glycol, sodium picosulfate was associated with a higher risk of hospitalization with hyponatremia (absolute risk increase: 0.05%, 95% confidence interval (CI): 0.04-0.06%, relative risk (RR): 2.4, 95% CI: 1.5-3.9), but not hospitalization with urgent CT head (RR: 1.1, 95% CI: 0.7-1.4) or mortality (RR: 0.9, 95% CI: 0.7-1.3).

Conclusions: Sodium picosulfate bowel preparations lead to more hyponatremia than polyethylene glycol. There was no evidence of increased risk of acute neurologic symptoms or mortality. The absolute increase in risk of hospitalization with hyponatremia remains low but may be avoidable through appropriate fluid intake or preferential use of polyethylene glycol in some older adults.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age Factors
  • Aged
  • Aged, 80 and over
  • Cathartics / adverse effects*
  • Citrates / adverse effects*
  • Cohort Studies
  • Colonoscopy
  • Female
  • Hospitalization / statistics & numerical data
  • Humans
  • Hyponatremia / chemically induced*
  • Hyponatremia / mortality
  • Male
  • Nervous System Diseases / chemically induced
  • Nervous System Diseases / diagnostic imaging
  • Nervous System Diseases / mortality
  • Organometallic Compounds / adverse effects*
  • Picolines / adverse effects*
  • Polyethylene Glycols / adverse effects
  • Retrospective Studies
  • Risk Factors
  • Tomography, X-Ray Computed


  • Cathartics
  • Citrates
  • Organometallic Compounds
  • Picolines
  • Polyethylene Glycols
  • picosulfate sodium