Quality control in the production process and purity of ²²⁴Ra for injection

Abstract

Buchler & Co. (since 1971 Amersham Buchler) are as far as we know the only producer of ²²⁴Ra for injection. ²²⁴Ra is the daughter product of ²²⁸Th. We separate ²²⁴Ra from ²²⁸Th by a specially developed chemical method. As the long-lived radionuclides in ²²⁴Ra injection are of high radiation risk to the patient, so is the quality control of these impurities in the final product of the greatest importance. The possible long-lived impurities in the ²²⁴Ra solutions are ²²⁶Ra, ²²⁸Ra, ²²⁷Ac, ²²⁸Th and ²¹⁰Pb.

The ²²⁸Th must be purified from any long-lived impurities through chemical processes before final extraction of ²²⁴Ra. Only with the exact determination of the amount of these impurities the ²²⁸Th can be used for the ²²⁴Ra production. The amount of ²²⁸Th must therefore be ascertained before release of the final product. A single injection of 28 μCi ²²⁴Ra per patient weekly with a maximum total dosage of 280 μCi is recommended.

We compare the detected long-lived radioactive impurities in 280 μCi ²²⁴Ra injection-solutions with the maximum values accepted by ICRP. The actual amounts of impurities present are less than 0,2% of the permissible doses recommended by ICRP.

The ²²⁴Ra solution is sterilised in an autoclave to a standard corresponding to that of the national pharmacopoeia. The measurement of the ²²⁴Ra solution is accomplished by evaluating the solution against a ²²⁶Ra standard.