A radioiodinated bretylium analog as a potential agent for scanning the adrenal medulla.

Studies with radioiodinated bretylium analogs (RIBA) suggested that the p-isomer was capable of concentrating in adrenal medulla. The present studies with 125I-p-RIBA in rats and dogs confirm this property and show its marked and persistent affinity for the adrenal medulla. Analogous studies with 14C-p-IBA indicate that it is the quaternary form of the drug that is retained by the adrenal and that high thyroidal radioactivity following 125I-p-RIBA administration is due to in vivo deiodination of the drug.