Synthesis of Hippuric Acid in Man Following Intravenous Injection of Sodium Benzoate

Abstract

With the increasing employment of the synthesis of hippuric acid as a means of determining liver function, several disadvantages of this test have been recognized. Vomiting occasionally occurs after the ingestion of sodium benzoate; the collection of urine for 4 hours is at times inconvenient; and in rare instances the condition of the patient may not permit the oral administration of the drug.

To meet these difficulties, the intravenous injection of sodium benzoate was investigated. 1.77 gm. of sodium benzoate (equivalent to 1.5 gm. benzoic acid) dissolved in 20 cc. of distilled water were given intravenously. The subject voided before the test began and a complete urine specimen was collected exactly one hour after the completion of the injection. Approximately 5 minutes were required for the injection. The hippuric acid was determined by the senior author's simple clinical method. 1 The results obtained on normal adult subjects are given in Table I.

From these results one can conclude that after the injection of 1.5 gm. of benzoic acid (as the sodium salt), 0.7 to 0.95 gm. are excreted as hippuric acid during the first hour by a healthy adult subject. If exogenous glycine is supplied, the synthesis of hippuric acid is greatly increased, which indicates that the amount of hippuric acid excreted is a measure of the body's capacity to synthesize glycine.