A Comparison of the Value of Ferrous Iodide Administered Directly and Indirectly. ∗

Abstract

Ferrous iodide has been administered orally as a tonic for many years in the practice of medicine without any evidence of toxicity when therapeutic doses are not exceeded. Recently, however, “toxicity” on direct oral administration has been ascribed to it in vitamin A deficient rats 1 in explanation of the negative results obtained by Mason, 2 Cameron, 3 and Mendel 4 when ferrous iodide was used as a substitute for vitamin A.

In all of these experiments, dilute ferrous iodide was given by pipette or syringe to rats depleted of vitamin A, a method which prompted the criticism of toxicity. In the following experiments, comparison is made of the effects of ferrous iodide when given by this method and when given as a part of the diet, thus avoiding any possible toxic effect of direct oral administration.

In these experiments dilute syrup of ferrous iodide alone or combined with linoleic acid has been given daily, mixed with a small amount of dry diet in a small glass dish left in the cage without other food until its contents was consumed. The results are compared with the earlier experiments in which direct oral administration was used. Standard vitamin A procedure was followed, 3 vitamin D being supplied throughout by the addition of 0.05 mg. of irradiated ergosterol per 1000 gm. of diet. At the first appearance of xerophthalmia, usually between the 8th and 9th weeks, administration of ferrous iodide or other supplement was begun and continued to the death of the animal when autopsy was done. Observations were made 3 times a week to detect improvement in the eyes. The following supplements were used: syrup of ferrous iodide diluted 1-350, 5 drops daily; linoleic acid, 4 to 6 drops; linoleic acid and dilute ferrous iodide mixed in equal amounts, 8 drops daily.

Conclusions. There is thus found to be no significant difference in response of animals to ferrous iodide fed by pipette or mixed in the diet, and no evidence of a “toxicity” factor from the former. Furthermore, no vitamin-A substituting effect is obtained with ferous iodide alone or combined with linoleic acid given either by pipette or mixed in the food.