Studies on the preparation and isomeric composition of 186Re- and 188Re-pentavalent rhenium dimercaptosuccinic acid complex.

The preparative conditions for 186Re(V)DMSA and 188Re(V)DMSA (DMSA = meso-dimercaptosuccinic acid), beta-emitting radiopharmaceuticals that have been shown to localize in medullary thyroid carcinoma, require modification depending on the amount of carrier rhenium and the chemical form and medium in which the rhenium is supplied. Preparative conditions are described for use with carrier-free 188ReO4- in saline, and for use with 186ReO4- in saline, sodium hydroxide or nitric acid. Preparation of 186Re(V)DMSA (carrier present up to 2 mg per 2.5 ml reaction volume) requires a DMSA:SnCl2:Re ratio of 10:5:1 at 100 degrees C for 30 min. Addition of excess nitric acid or hydrochloric acid up to a concentration of 155 mM does not reduce the yield from 100%. A commercial DMSA kit vial (e.g. Amerscan DMSA) can be used for preparation of 188Re(V)DMSA (carrier free) provided the required activity is in a volume of less than 1 ml per vial. A convenient method of concentrating the 188Re generator eluate to the required volume is described.