Sodium polystyrene sulfonate associated with GI events requiring hospitalization in elderly

An accompanying editorial said that based on the risk of gastrointestinal (GI) events found in this retrospective study, sodium polystyrene sulfonate should not be used to reduce serum potassium levels.

Sodium polystyrene sulfonate was associated with hospitalization for serious adverse gastrointestinal (GI) events among elderly patients, a recent study found.

The population-based, retrospective study included 27,704 patients age 66 years and older (mean age, 78.5 years; 54.7% male) who were prescribed sodium polystyrene sulfonate from April 1, 2003, to Sept. 30, 2015, in Ontario, Canada, with maximum follow-up to March 31, 2016. A cohort of 20,020 of them was matched to 20,020 similar patients who did not receive sodium polystyrene sulfonate. Results were published by JAMA Internal Medicine on June 10.

The study's primary outcome was a composite of adverse GI events—hospitalization or ED visit with intestinal ischemia/thrombosis, GI ulceration/perforation, or resection/ostomy—within 30 days of an initial sodium polystyrene sulfonate prescription. The outcome was significantly more common in patients taking sodium polystyrene sulfonate: 37 events (0.2%; incidence rate, 22.97 per 1,000 person-years) versus 18 events (0.1%; incidence rate, 11.01 per 1,000 person-years) in matched controls (hazard ratio, 1.94; 95% CI, 1.10 to 3.41). Intestinal ischemia or thrombosis was the most common type of GI injury.

Similar results were found regardless of kidney function or serum potassium level, presence of diabetes or congestive heart failure, use of renin-angiotensin aldosterone system blockade, or whether data came from before or after 2009, when the FDA warned against using sodium polystyrene sulfonate concurrently with 70% sorbitol. These results suggest that sorbitol was not entirely responsible for the previously observed risk of GI events, the authors said. They noted that the lack of risk difference among subgroups in this study could be due to sample size limitations.

The authors said that, to their knowledge, this is the first population-based study to investigate the association between sodium polystyrene sulfonate and serious adverse GI events, after previous smaller investigations have provided uncertain evidence. “These findings require confirmation and suggest caution with the ongoing use of sodium polystyrene sulfonate,” the authors said.

An accompanying editorial went further. “Given the evidence, sodium polystyrene sulfonate should not be used to reduce serum potassium levels. There are a number of other approaches to treating elevated serum potassium levels, including dietary restriction of potassium, potassium-wasting diuretics, and lower doses or discontinuation of medications that increase serum potassium,” it said. An alternative, similar drug (patiromer) was recently approved, but studies of it have been small and short term, the editorial said.

The editorialists did note limitations of the study, including the age and comorbidities of the patients included, and they said that the risk for GI events might be lower in younger, healthier patients. The study also did not include data on medication doses or adherence or pathologic characteristics, making it hard to establish a dose-response relationship or causation, the editorial said.