Renal risks of sodium phosphate tablets for colonoscopy preparation: a review of adverse drug reactions reported to the US Food and Drug Administration

Abstract

Sodium-phosphate-containing colonoscopy preparations cause renal failure by the development of calcium phosphate nephropathy. Although Fleet's Phospho-Soda has been removed from the US market, sodium phosphate tablets sold as OsmoPrep and Visicol remain available. Our aim was to analyse renal risks of the sodium phosphate tablets. We conducted a retrospective study using the US Food and Drug Administration Adverse Event Reporting System, a voluntary reporting system available for public access. Renal adverse events were identified using search terms including renal impairment, increased blood urea nitrogen, increased creatinine, renal failure, acute renal failure, chronic renal failure, acute phosphate nephropathy, nephrocalcinosis, renal tubular necrosis, haemodialysis, nephropathy toxic, dialysis, peritoneal dialysis, renal injury, renal tubular disorder, decreased glomerular filtration rate and decreased creatinine clearance. Patient age, gender and body weight were compared with data for the general population in the National Health and Nutrition Examination Survey (NHANES). In total 2,097,223 files were extracted from the US Food and Drug Administration website for 2004-2008 and the first 9 months of 2009. Of these, 178 patients on tablet preparations (71% women) were identified, with increasing numbers of renal adverse drug reactions reported from tablet preparations each year. The mean weight for women with renal complications from tablet preparations was 68.57 ± 1.78 kg, significantly lower than the national average weight of 74 ± 0.5 kg for the same age group (P = 0.003) in NHANES. Renal adverse drug reactions from sodium phosphate tablets are more common in women with a mean body weight lower than the national average weight.