Validation of the preparation of individual doses of I-131-sodium o-iodohippurate (I-131-hippuran)

The preparation of low activity doses of I-131-hippuran has a drawback due to its high radioactivity concentration. In this study we diluted the radio pharmaceutical with saline or phosphate buffered saline (PBS) in order to d ecrease the radioactivity concentration, facilitate the preparation of indi vidual doses and validate these procedures. We prepared doses of approx. 1. 85 MBq of I-131-hippuran from 10 different batches the day before the calib ration date: undiluted, and diluted 1:9 with saline or PBS. The radiochemic al purity (RCP) was evaluated the day after the expiry date. The percentage of I-131-hippuran retained on syringes was assessed in vitro, after emptyi ng the syringe and washing it twice with water (n =3 x 27); and in vivo, af ter the endovenous administration of the dose and washing the syringe twice with the patient's blood (n =3 x 75). Sterility was assessed using fluid t hyoglicolate medium (n = 3 x 15). All RCP values were greater than those re quired by the European Pharmacopoeia (>96%) except one of the undiluted I-1 31-hippuran (95.8%) doses. No statistical difference was observed among the m. The mean undiluted I-131-hippuran retained in vitro was 5.4% (SD = 6.5%) , statistically greater (P<0.01) than both saline diluted (mean=1.5%, SD=1. 1%) and PBS diluted (mean=2.0%, SD=2.4%). The mean undiluted I-131-hippuran retained in vivo was 6.4% (SD=5.4%), statistically greater (P<10(-5)) than both saline diluted (mean =3.1%, SD =2.3%) and PBS diluted (mean =3.1%, SD =3.1%). We concluded that: (1) the dilution of I-131-hippuran with saline o r PBS makes both the preparation of individual doses and its administration to the patient easier without decreasing its radiopharmaceutical quality; and (2) using saline or PBS diluted I-131-hippuran the percentage of radiop harmaceutical retained on the syringes, after use, is minimized. ((C) 2001 Lippincott Williams & Wilkins).