The Effects of the Rate of Administration of Amino Acid Preparations on Urinary Wastage of Amino Acid Nitrogen in Man.

One of the major objections to the clinical use of mixtures of amino acids derived from hydrolysis of casein is the occurrence of nausea, vomiting, flushing, and headaches. These undesirable symptoms occur more frequently if the rate of administration is rapid. In a previous communication (1) it was shown that the elimination of many of these reactions could be accomplished by reducing the rate of infusion; it was further observed that mixtures of amino acids could be given at exceedingly rapid rates (100 ml. of a 10 per cent mixture per minute or the equivalent of 100 grams of protein could be given intravenously in less than three hours) without causing any discomfort to the patient. Earlier investigators (2, 3, 4) found that if amino acid preparations were given intravenously at a slow rate, usually less than 8 per cent of the administered amino acid nitrogen was lost by urinary spillage. Thus, it was desirous to learn whether the advantages gained by the rapid intravenous infusion of the well-tolerated amino acid mixtures might be offset by an increased urinary loss. This study was planned to compare the urinary amino acid nitrogen loss following the intravenous administration of amino acid mixtures at rapid rates with the loss which occurred following the intravenous injection of casein digests at rates approaching maximum tolerance. In addition, studies were designed to obtain comparable control data regarding the amount of amino acid nitrogen lost due to the "washing-out" effect following the injection of equal volumes of physiological saline.