TRANSMISSION from mother to child of iophenoxic acid (Teridax), a gallbladder contrast media, is now established,1,2 and the fact that in one of our cases no nursing took place indicates that transmission is placental. Our experience with patients referred for clarification of thyroid studies leads us to the opinion that the problems posed by this substance are the proper basis for a brief note. This opinion is reinforced by the observation that several recent reviews of clinical tests of thyroid function make no mention of iophenoxic acid.
Astwood3 called attention to the special peculiarities of iophenoxic acid in 1957. It is apparently unique in its resistance to deiodination and, hence, both in its persistence in the body and in its failure to depress thyroid radioiodine uptake. The half-life of this substance appears to be 2 to 2½ years in the patients receiving the contrast media, and perhaps