Effect of Butazolidin ∗ upon the Fate of I 131 in the Rat

Abstract

During the course of the evaluation of other drugs upon the thyroidal accumulation of iodine in patients, it was observed that a patient being given butazolidin^R had a very low I¹³¹ thyroid uptake. In this study rats were used in order to measure more completely the effect of this drug upon iodine metabolism.

Methods. Young albino rats were given butazolidine^R by subcutaneous injection at dosage levels ranging from 8 to 200 mg/kg body weight. In some groups of animals this was followed immediately by a tracer dose of 5 μc of I¹³¹ intraperitoneally. No additional iodide was added in these studies; thus the administration of the I¹³¹ served only to label the iodide pool of the body. The total amount of iodide present in 5 μc of I¹³¹ is calculated to be less than 1 × 10^-3 μg. As will be noted in Table I, the uptake of I¹³ by control animals varied as much as 100%. Although the experimental and control animals for each group are of the same lot and origin, both Sprague Dawley and Slonaker strains of rats were employed in the several experiments combined in Table I. In our hands, Sprague Dawley rats recently received from Wisconsin have much higher thyroid uptake of I¹³¹ than that observed in rats bred locally. We believe that this merely represents a smaller iodide pool in rats imported from the Midwest since this higher uptake is reduced to that seen in local rats after a period of several weeks in their new environment. These animals were sacrificed 20 hours following I131 administration. Other groups of rats were given the drug daily for periods of 10 to 16 days in which the last injection of the drug was followed by 5 μc of I¹³¹.