Kit method of preparation of 4-lodoantipyrine (I-123) from Na123I: concise communication.

4-Iodoantipyrine (4-IAP), containing 123I, has been suggested as a radio-pharmaceutical for direct imaging of regional cerebral perfusion. In routine clinical use, a reliable source of the labeled compound is required. The 4-IAP (I-123) can be prepared by exchange between Na123I and 4-bromoantipyrine (4-BrAP) or 4-IAP with heating in aqueous acidic solution. Using an H3PO4 buffer system at pH 2.5 during labeling, with addition of NaOH for subsequent buffering at pH 7.0, a convenient reliable kit for routine preparation of 4-IAP (I-123) from commercially available Na123I has been developed.