Jeanatope is iodinated I-125 human serum albumin, typically injected to aid in the determination of total blood and plasma volume. I-125 is a radioactive isotope of Iodine, it decays by electron capture with a physical half-life of 60.14 days. The biologic half-life in normal individuals for I-125 has been reported to be approximately 14 days.
Iodinated I-131 albumin (Volumex, Daxor) is used for a similar purpose.
References
Jeanatope Wikipedia(Text) CC BY-SA