Influence of iodine-131 solution volume and storage time on in vitro dissolution

This investigation was conducted to determine the influence of 131I solution volume and storage time on the in vitro release of radioiodide from capsules. In vitro dissolution profiles for 131I sodium iodide capsules compounded in a centralized nuclear pharmacy were determined using the USP XXIII Dissolution Test. Iodine-131 solution volumes of 0.05, 0.15 and 0.25 ml and storage times of 2, 5, 7 and 9 days were considered. By 80 min after initiation of the dissolution test, more than 95% of the 131I was released from capsules prepared with 0.15 and 0.25 ml of the 131I solution. The 0.05-ml capsules reached 95% at 55 min. Capsules prepared with 0.05 ml of solution and stored 2, 5, 7 or 9 days released over 95% of the radioactivity within 65 min. Capsules prepared with 0.25 ml of solution and stored for 2, 5, 7 or 9 days released over 95% of the 131I by 55 min after initiation of the dissolution test. Neither the different volume of radioactive sodium iodide solution used in the preparation of capsules nor the time of storage greatly influenced the release of 131I from the capsules. Based on dissolution profiles, it appears that the bioavailability of 131I would not be influenced by factors studied in this investigation.