Recommendations for Sterility Testing of Radiopharmaceuticals

In view of the difficulties in applying the European Pharmacopeia test, many variations have been adopted. Whatever the technique used, it is essential to perform a validation to ensure that it would be able to detect the presence of any viable microorganisms in the sample. 

The membrane filtration technique is technically more elaborate and requires that the radiopharmaceutical under test, after aseptic dilution, is passed through a membrane filter with a pore size of 0.45 m, which has been moistened with a sterile nutrient diluent. After filtration, the membrane is either transferred to a suitable culture medium or aseptically cut into two equal parts and one half placed in each of two suitable media. Incubation at the appropriate temperature is required for at least 7 days. 

An alternative - although unofficial - technique that has been used is the addition of an equal volume of double-strength culture medium directly to the remnants of the vial of radiopharmaceutical immediately upon its expiration. The advantages and disadvantages of this technique are summarized in Table 9.3.1. 

In order to make the test more meaningful, it is necessary to rotate the culture media used and ensure that each product prepared is at some stage tested with each culture me- 

No delay in testing Can be performed in radiopharmacy Container can be easily shielded No dilution of culture medium below normal strength Sample size variable Only one culture medium can be used Not officially recognized Not applicable if preservatives need to be diluted out 

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