THE EXCRETION OF AMPHETAMINE

¹ From the Department of Physiology, Northwestern University Medical School, Chicago

The data reveal that when 30 mgm. of dl-amphetamine (Benzedrine) or 15 mgm. of d-amphetamine (Dexedrine) were given daily to 10 human subjects for 56 consecutive days, the daily urinary excretion of the drugs remained essentially constant. These results imply that the rate of catabolism of the drug (presumably by the liver) remained constant, and that the development of tolerance cannot be attributed to progressive changes in drug destruction.

Under the conditions of the experiment, there was no evidence of a diuretic effect of amphetamine and the excretion of the drug was independent of urinary volume.

Although it has been reported that ascorbic acid will decrease the urinary excretion of amphetamine by dogs, it was found that amphetamine did not reduce the blood level of ascorbic acid.

PROCEDURE. Ten healthy male medical students served as subjects for this experiment. Each was of normal body weight. The subjects were fed three meals a day by a diet kitchen operated solely for this group. They were required to eat all the food served to them without exception or extramural addition. The menu was arranged to provide a constant daily caloric, mineral, vitamin, protein, fat and carbohydrate intake. Coffee was permitted but the quantity imbibed remained constant throughout the experiment as did the smoking habit of those who indulged.

During the first two weeks no capsules were given. During the third and fourth weeks placebos were issued. Medication began the fifth week. Five subjects (no. 1 to 5) received 10 mgm. of dl-amphetamine (Benzedrine) and five (no. 6 to 10) received 5 mgm. of d-amphetamine (Dexedrine) three times a day. This medication was given one hour before each meal and was continued for 56 consecutive days. The program was continued for two more weeks during which placehos were again given. All urine was collected and each 24-hour sample was assayed for its total amphetamine content.

The assay method for the determination of amphetamine in urine developed by Beyer (4) gave inconsistent results in our hands.

Our method was the same as that of Jacobsen and Gad (2), except the distillation step was replaced by one in which interfering substances were adsorbed on MgO in a buffered medium, and the petroleum ether in which the color reaction was developed was dried with anhydrous sodium sulfate. This latter step is essential to consistent results as mere traces of water will give considerable color in the petroleum ether, chloroform, picric acid solution.

Our procedure is as follows: (1) Measure the 24 hour urine sample to the nearest 5 cc. (2) Place 25 cc. of urine in a 125 cc. glass-stoppered Erlenmeyer flask. (3) Add 25 cc. of McIlvaine's solution (6) buffered to pH 6.4 and 100 mgm. of magnesium oxide. (4) Shake for 5 minutes in mechanical shaker. (5) Filter using Whatman's #1 paper. (6) Add 4 cc. 10 per cent sodium hydroxide, mix thoroughly, and filter again. (7) Extract 40 cc. of this filtrate with two portions, 25 cc. each, of redistilled Skellsol "C" (Petroleum ether, B. P. 94°C.). (8). Pool these extracts and add 5 grams of anhydrous sodium sulfate powder (9) Allow to stand overnight for the purpose of drying. (10) To 5 cc. of the dehyrated petroleum ether extract add 5 cc. of dry picric acid in chloroform solution (1 mgm. per cc.). (11) After 20 minutes read in the colorimeter (Coleman Universal Spectrophotometer) at a wave length of 420 mµ against a blank which contains 5 cc. of water-free petroleum ether and 5 cc. of picric acid in chloroform solution.

The Standard Curve for the amphetamine determination in urine was prepared as follows:

Prepare a standard solution of amphetamine in water (0.01 mgm. per cc.). Make a series of 50 cc. volumetric flasks, containing 0, 0.4, 0.8, 1.2, 1.6, 2.0 mgm. of amphetamine. Make the volume of each flask up to 50 cc. with the buffered solution (pH 6.4). Add 100 mgm. of MgO and proceed with step No. 4 as in the method described above. When the colorimeter readings are plotted against the concentrations on semi-logarithmic paper, the relationship is linear.