Objectives: Constipation is highly prevalent in advanced chronic kidney disease (CKD),
due in part to dietary (e.g., fiber) restrictions, and is often managed by laxatives;
however, the effect of laxative use on kidney function in advanced CKD remains unclear.
We aimed to examine the association of laxative use with longitudinal change in estimated
glomerular filtration rate (eGFR) in patients with advanced CKD. Design and Methods:
In a retrospective cohort of 43,622 US veterans transitioning to end-stage renal disease
(ESRD) from 2007 to 2015, we estimated changes in eGFR (slope) by linear mixed-effects
models using $2 available outpatient eGFR measurements during the 2-year period before
transition to ESRD. The association of laxative use with change in eGFR was examined
by testing the interaction of time-varying laxative use with time for eGFR slope in
the mixed-effects models with adjustment for fixed and time-varying confounders. Results:
Laxatives were prescribed in 49.8% of patients during the last 2-year pre-ESRD period.
In the crude model, time-varying laxative use was modestly associated with more progressive
eGFR decline compared with non-use of laxatives (median [interquartile interval] -7.1
[-11.9, -4.3] vs. -6.8 [-11.6, -4.0] mL/min/1.73 m2/year, P < .001). After multivariable
adjustment, a faster eGFR decline associated with laxative use (vs. non-use of laxatives)
remained statistically significant, although the between-group difference in eGFR
slope was minimal (median [interquartile interval] -8.8 [-12.9, -5.9] vs. -8.6 [-12.6,
-5.6] mL/min/1.73 m2/year, P < .001). The significant association was no longer evident
across different types of laxatives (i.e., stool softeners, stimulants, or hyperosmotics).
Conclusions: There was a clinically negligible association of laxative use with change
in eGFR during the last 2-year pre-ESRD period, suggesting the renal safety profile
of laxatives in advanced CKD patients. Published by Elsevier Inc. on behalf of the
National Kidney Foundation, Inc.
