Age as a predictor of hyperphosphatemia after oral phosphosoda administration for colon preparation

It has been reported that oral phosphosoda (OPS), commonly used in bowel cleansing, may cause complications such as hyperphosphatemia and hypocalcemia. This has been observed in patients with normal kidney function and in those with renal insufficiency. Few controlled studies have been performed with respect to age on healthy subjects after OPS administration.

Seventy patients (38 men and 32 women; mean age 47 +/- 12 years, range 25-80 years) were enrolled in the present study. Half of the 90 mL total volume of OPS was ingested 18 h before colonoscopy, and the other half 6 h before the procedure. Creatinine clearance rate (CCR) and serum levels of sodium, potassium, calcium and phosphate were measured before and after OPS administration.

After OPS administration, serum calcium and potassium were significantly lower (P < 0.05), and serum phosphate and sodium were significantly higher than pretreatment levels (P < or = 0.01). The statistically significant changes in serum sodium, potassium and calcium were within normal laboratory ranges. The mean change in serum phosphate was positively correlated with age (Pearson's r = 0.705; p < 0.001).

Administration of OPS causes a significant rise in serum phosphate, even in patients with normal CCR. The elevation is significantly greater in elderly patients. Administration of OPS can be considered safe for young and middle-aged patients with normal renal function; however, it should be used with caution in elderly patients, even in those with normal CCR and serum creatinine values.