Iobenguane I 131 (CAS NO.: ), with its systematic name of (m-Iodo-(sup 131)I-benzyl)guanidine, could be produced through many synthetic methods.

Following is one of the synthesis routes:

A mixture of m-iodobenzylamine (I) hydrochloride and cyanamide (II) is stirred and heated at 100 C for 4h. The resulting m-iodobenzylguanidine is converted to the bicarbonate salt by treatment with aqueous potassium bicarbonate. Addition of dilute sulfuric acid gives the guanidine sulfate. To prepare the labeled compound, the unlabeled m-iodobenzylguanidinium sulfate is dissolved in water and treated with carrier-free Na[131]I. Refluxing for 72h and passage through Cellex D anion exchange cellulose gives [131]iodobenzylguanidine sulfate. Another more efficient method of carrying out the exchange-labeling step has been reported.