ABOUT THE FATE OF FREE IODINE UPON APPLICATION TO THE UNBROKEN ANIMAL SKIN AN EXPERIMENTAL STUDY

¹ From the Research Laboratories of the New Jersey College of Pharmacy, Rutgers University

The paper deals with the fate of free iodine upon application to the unbroken animal skin. The experiments were made on rabbits and dogs, and gave the following results:

1. Free iodine pentrates through the unbroken skin. This penetration only takes place in the form of compounds. Iodine upon external application was detected (a) in the urine of dogs, (b) on the inner surface of the pouched rabbit skin, (c) in the efferent blood vessels of the perfused isolated rabbit ear.

2. Quantitative experiments made on rabbits concerning penetration, absorption and evaporation of iodine offer a fair conception concerning the fate of iodine applied to the surface of animal skin:

a. Approximately 88 per cent of the iodine evaporate from the surface within three days. The rate of evaporation is highest within the first few minutes after application. Within the first two hours 50 per cent of the material escape into the air; at the end of twenty-four hours the loss amounts to about 75 to 80 per cent; only small amounts evaporate during the second day, and even less during the third day. The evaporation ceases after this time.

b. The rest, approximately 12 per cent is at the disposal of the body, and penetrates through the skin. The removal of these 12 per cent into the body is very gradual. Only 1 to 4 per cent are absorbed within the first few hours. The rest forms a depôt in the skin from which about 5 to 6 per cent are taken up within three days. The remaining 3 to 5 per cent are gradually absorbed after this time.

3. Following application to the skin of the dog, 1 to 3 per cent of iodine are excreted in the urine within three days. Although this percentage is very low, it suggests that the fate of iodine in the dog is similar to that in the rabbit, considering the slow rate of urinary excretion following various modes of administration, and the marked iodine storing power of the body.

4. The percentage of iodine penetration through the skin is the same, irrespective of whether the cells have a high or low vitality, or are dead, and irrespective of the direction of penetration. Activity of the cells, therefore, does not seem to be indispensable for the penetration of iodine.

5. The fate of iodine in all above experiments is the same whether iodine is applied to the skin in the form of an alcoholic solution or in colloidal suspension.

6. When the isolated ear and isolated kidney of rabbits are perfused at a moderate rate with a solution containing free iodine, the iodine is quantitatively reduced to iodides.

The paper serves as experimental evidence for the penetration of iodine through the unbroken animal skin.