Eco-friendly semi-automated sterility testing method for injectable radiopharmaceuticals - feasibility study and validation

Various diagnostic and therapeutic radiopharmaceuticals are regularly supplied for clinical use across India by BRIT. BRIT QA/QC monographs and Indian Pharmacopeia approve parametric release of short lived injectable radiopharmaceuticals as it is not feasible to complete the Sterility Test (ST) before the product is released. However, as a good manufacturing practice, it is mandatory that the test be commenced at the earliest. Conventional methodology for ST involves manual transfer of test samples - minimum four vials per batch-into sterile growth media under aseptic conditions. This method is time-consuming, requires skilled persons and results in considerable radiation exposure to analyst in routine testing facilities. We describe here a simple vacuum-based manifold system which was designed in house, validated and tested in routine use to circumvent these problems. In order to make this test economical and environmentally friendly, spent consumables discarded as waste from the ⁶⁸Ga-radiopharmaceuticals production facility were reused by sterilising them by means of gamma radiation in the Radiation Processing Plant (RPP), BRIT. The vacuum-based manifold system consisted of four silicone tubings (Masterflex) connected to a vacuum pump and attached to sterile needles. These needles were introduced into Fluid Thioglycollate Medium (FTM) and Soyabean Casein Digest Medium (SCD) bottles (HiMedia Laboratories). Sterile assemblies containing a spinal needle (18G) connected to a sterile needle (23G) via silicone tubing were used. These assemblies were obtained from the waste generated from the ⁶⁸Ge-⁶⁸Ga generator after production of ⁶⁸Ga radiopharmaceuticals, allowed to decay until certified to be inactive and then cleaned by rinsing with sterile Water for Injection. These were sterilised by gamma radiation at RPP, BRIT by using a radiation dose of 25 kGy. This dose is suitable for sterilization purposes, chosen based on radiation resistance of bacterial spores of the radio-resistant micro-organsim, Bacillus pumilus. The 25 kGy dose is higher than necessary for achieving sterility and reaching a Sterility Assurance Level of 10^-6 (SAL, one micro-organism surviving after treatment in a sample of 10⁶ micro-organisms, or one non-sterile item after sterilization of a batch of 10⁶). The spinal needles were introduced into the sample vials such that their tip touched the base of the vials. Individual vacuum control for each of the four sets was done using solenoid valves placed between the media bottles and the vacuum trap. Switching on the vacuum and respective solenoid valve ensured withdrawal of the entire sample volume through the spinal needle and tubing into the media vial. Test samples were housed in slotted lead stand of appropriate thickness. The whole assembly was set up inside a Biosafety Cabinet (Class III). The inoculated media were incubated at 30-35℃ and 20-25℃ respectively for 14 days and examined for microbial growth by visual examination. Sterile saline was used to inoculate the media in the same manner and used as controls. The radiopharmaceuticals tested by this method included: ¹⁵³Sm-EDTMP, ¹³¹I-mIBG and Na^99mTcO₄ eluates from ⁹⁰Mo-^99mTc generators (04 batches each, RAC ~20 mCi/mL (740 MBq/mL) per vial). All the injectable radiopharmaceutical products tested passed the ST as indicated by absence of microbial growth on completion of the 14 days incubation period. The adaptation of the ST method using a vacuum manifold, besides being safe and time saving, provides a reliable quality control testing option for radiopharmaceuticals and decreases personal errors. Recycling the waste from the ⁶⁸Ge-⁶⁸Ga generator for use as consumables for this test will result in cost-saving as a result of the potential for in house re-use of these materials as well as considerable reduction in the quantum of environmental waste generated. This method can result in a significant reduction in the radiation dose received by the analyst and provides a feasible alternative to the conventional method. (author)