the time course and effect on serum electrolytes of oral sodium phosphates solution in healthy male and female volunteers background although oral sodium phosphates solution is used extensively for bowel preparation the pharmacokinetic profile of 2 x 45 ml oral sodium phosphates solution has not been reportedobjectives the primary objective of this study was to evaluate the time course and degree of electrolyte shifts in two age groups and two gender groups following administration of oral sodium phosphates solution secondary objectives included evaluation of electrocardiograms postural blood pressure standard serum chemistry and hematology panels and adverse experiencesmethods twentyfour healthy adult volunteers were divided equally into groups based on age and gender each received 2 x 45 ml oral sodium phosphates solution at 700pm hour 0 and at 700am hour 12 serum electrolytes were measured at sixteen different time pointsresults mean serum phosphate concentrations exceeded the upper normal limit within 1 hour following the first dose peaking at 3 hours 626 mgdl p 00001 before decreasing following the second dose at 12 hours mean serum phosphate concentrations peaked at 14 hours 686 mgdl p 00001 before decreasing to normal limits by hour 24 mean serum sodium potassium and calcium concentrations fluctuated within the normal range however serum sodium concentrations peaked at 1 hour following the second dose of phosphate showing a statistically significant p 00001 increase of 24 from baseline to 1448 mmoll no clinically significant changes in ecg were observed mean reductions in supine and standing systolic blood pressure were not associated with postural change no subject had postural decreases in systolic blood pressure of greater than 20 mmhgconclusions administration of 2 x 45 ml oral sodium phosphates solution 12 hours apart with proper hydration caused transient serum electrolyte shifts which were clinically insignificant and resolved within 24 hours