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The need for a suitable pyrogen test for radiopharmaceuticals led Cooper, Levin and Wagner to define the role of Limulus amebocyte lysate (LAL) reagent as a way to test injectables for endotoxin. At SNM in June 1971, we first described LAL tests for radiopharmaceuticals. The US Pharmacopeia replaced the rabbit bioassay with the BET (Bacterial Endotoxins Test) in 1984, beginning with 29 monographs for radiopharmaceuticals and waters. Also, pyrogenic reactions to intraspinal I-131 albumin led to strict endotoxin limits for intrathecal drugs.
Today we describe a novel endotoxin test known as Portable Test SystemTM (PTSTM).
Endotoxin comes from Gram (-) bacteria growing on wet surfaces, such as glassware, tubing and resins; unfortunately, it passes sterilizing membrane filters. Key steps to prevent pyrogens include sterile components, depyrogenation and aseptic technique.
PTSTM is a portable, automated spectrophotometer for quantitative analysis and reporting of endotoxin concentration. It analyses a unique cartridge containing dry, pre-calibrated reagents. Each cartridge contains duplicate channels for analysis of sample and positive control (USP). PTSTM is particularly suited for PET drugs because it requires only 15 minutes, <0.1 mL of undiluted product and NO preparation of endotoxin standards.
In the absence of FDA regulation for PET, PTS may be used by applying USP Chapters <85> BET <823> for PET drug production.
Results: Validation of Endotoxin Test Conditions. We determinate the least dilution for each of eight (8) PET drugs that was needed to recover an endotoxin spike in a PTSTM without interference, that is, recovery of 50-to-200% of the PPC. (Table 1)
Table 1. Results of PTS Validation study for PET drugs
RN PET MED Dilution LOD* PC % Recovery
18F FDG 10 0.5 79-103 (91)
18F FLT 10 0.5 100-107 (103)
18F FLuoride 10 0.5 110-124 (120)
18F FDOPA 10 0.5 80-1140 (112)
13N Ammonia 20 1 99-122 (108)
11C Acetate 20 1 129-182 (150)
11C Methionine 20 1 84-107 (95)
11C Raclopride 20 1 68-121 (100)
*Limit of Detection (Eu/mL) when reagent sensitivity is 0.05 EU/mL
At MGH, a dilution of 1:10 was validated for 18F labeled to fludeoxyglucose (FDG), fluoride (F), fluorothymidine (FLT),and fluoro-l-dopa (FDOPA). A 1:20 dilution was validated for 13N-ammonia (NH3), 11C labeled to acetate (AC), methionine and raclopride. And 1:40 dilution for 123IMIBG. At U. of Michigan, Dave Hubers Achieved similar results. These results were confirmed using kinetic chromogenic assay on a microplate reader. No endotoxin was seen in validation samples.
Limit of detection was 0.5 to 2EU/mL where the Endotoxin Limit was 14 EU/mL. Note that the EL is maximum safe endotoxin dose, where in the USP, 175 EU is divided by the maximum dose volume.
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