Comparison of compounded and commercial chromic phosphate P 32 suspensions

Objectives To make chromic phosphate P 32 as a true colloid and with properties equivalent to the commercial product that was removed from the US market in August 2009. The compounding of this radiopharmaceutical keeps this important therapeutic option available for physicians and their patients.

Methods Three batches of chromic phosphate P 32 suspensions were made by binding P 32 solution to chromium oxide, and then excess P 32 was removed. The particles were reduced to a 0.1-µm size by grinding, centrifuging, and filtering processes. Sodium sulfite was added forming a colloid and a protective gelatin coating was added to the colloidal particles. Samples from each batch were placed in a 10-mL empty sterile vial and marked A, B, C then autoclaved. Each batch was tested for radiochemical purity (RCP) using ITLC and a radio-TLC strip scanner (Bicron 3000). Approximately 5-µL of sample was placed onto a carbon coated grid and allowed to completely dry. The grid was then washed (3X) with distilled water to dissolve the salt crystals and allowed to dry prior to evaluation in the electron microscope (FEI Tecnai 12). A hemocytometer with a 40-µm grid was used to verify particle size (< 1 µm) under a light microscope. pH measurement, bacterial endotoxins test, and sterility test were also carried out for each batch. A fourth sample was taken from a vial of Phosphocol P 32 (Covidien, Hazelwood, MO) and labeled M as a reference standard.

Results The three batches of compounded chromic phosphate P 32 A, B, and C preparations were measured against the commercial Phosphocol P 32 suspension. RCP on each of 4 batches was found to be 100%, particle size was determined to be 0.1 to 0.3 µm, pH was 5.0, endotoxins level was less than 2 EU/mL, no bacterial, mold, or fungal growth observed at 14 days after inoculation.

Conclusions The compounded chromic phosphate P 32 microaggragate was found to be comparable to the commercial Phosphocol P 32 suspension in all critical quality attributes. A macroaggragate size of chromic phosphate P 32 has also been made by reducing the particle size to a 1-um size