Six female students were orally given 175 and 350ml of a soft drink containing 190mg/L of sodium benzoate (BA-Na) and three male volunteers were also orally given BA-Na solution at a dosage of 20mg/kg body weight. Urinary hippuric acid (HA) and creatinine excreted by the subjects given either the soft drink or the BA-Na solution were determined simultaneously by high performance liquid chromatography (HPLC) from the end of the administration until 4 or 5hr later, at appropriate intervals.
In the case of soft drink administration, the concentration of HA attained a maximum in urine taken from 0 to 30min and recovered to the predose level after 3hr. The molar ratios of HA excreted in the 0-3hr urine samples to the administered dose were estimated to be 66-86%, by subtracting the amount of HA excreted in the predose period on the day of the administration. In the case of BA-Na solution administration, the concentration of HA attained a maximum in the 0-1hr urine samples and did not recover to the predose level within 5hr. The molar ratio of HA excreted in the 0-5hr urine samples to the administered dose was estimated to be about 89%, by subtracting the amount of HA excreted in the predose period on the day of the administration. Based upon these findings, it is suggested that the amount of absorbed BA-Na in human subjects can be estimated by determining the amount of HA excreted in the urine.