Phosphates

Observational studies

In 194 patients randomized to receive either sodium picosulfate or fleet phosphate soda before barium enema, there was no difference in the quality of bowel preparation, but picosulfate was easier to take and better tasting and it provoked less nausea and vomiting [ ].

Comparative studies

Sodium phosphate and polyethylene glycol have been compared in 94 adults undergoing colonoscopy [ ]. Polyethylene glycol caused significant reductions in serum potassium, calcium, phosphorus, magnesium, bicarbonate, and blood urea nitrogen, and increases in sodium and phosphate. The proportional changes in those who used sodium phosphate were greater. In particular, in 37 of the patients who used sodium phosphate and 11 of those who used polyethylene glycol, phosphate concentrations increased by over 5%. Patients who took polyethylene glycol reported more adverse reactions, including nausea, vomiting, abdominal cramps and distension, anal irritation, sleeplessness, and chills. All of these symptoms were also seen in the sodium phosphate group, but significantly less often. The authors recommended that while sodium phosphate seemed to be more acceptable to patients, it should only be used with clinical supervision and after screening carefully for cardiovascular, hepatic, and renal disease, and should not be used with medications that would exacerbate electrolyte disturbances, such as diuretics, or with drugs that electrolyte disturbances would affect, such as digoxin and lithium.

In 340 patients undergoing elective colonoscopy, sodium phosphate was compared with polyethylene glycol with added ascorbic acid [ ]. Polyethylene glycol was at least as efficacious as sodium phosphate. Of all adverse events reported five were in those who took polyethylene glycol and 24 in those who took sodium phosphate. The most common in the former was vomiting and in the latter hyperphosphatemia and hypokalemia; two cases of hypokalemia were classified as serious.

Systematic reviews

Three types of bowel preparations for colonoscopy (sodium phosphate, polyethylene glycol, and sodium picosulfate) have been compared in a meta-analysis of 29 trials in a total of 6459 patients [ ]. Sodium phosphate was the most effective at cleansing the colon and was better tolerated than polyethylene glycol. Sodium picosulfate had similar efficacy to polyethylene glycol. There were adverse events in 1054/1662 patients who took polyethylene glycol and 902/1590 who took sodium phosphate. More patients developed dizziness with sodium phosphate than polyethylene glycol, abdominal pain was more common with polyethylene glycol, and both groups had similar amounts of nausea, vomiting, and perianal pain. When polyethylene glycol was compared with sodium picosulfate (104 and 112 patients respectively) polyethylene glycol produced more nausea, vomiting, abdominal pain, sleep disturbance, and perianal irritation than sodium picosulfate; 71% of patients who took polyethylene glycol reported adverse events compared with 48% of those who took sodium picosulfate. In comparisons of sodium phosphate and sodium picosulfate, there were similar amounts of nausea, vomiting, dizziness, and abdominal pain.