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Most radiopharmaceuticals are administered by intravenous injection and to ensure that there is no possibility that patients might be infected by micro-organisms in the preparation, it is essential that they are sterile at the time of administration.

This requirement is true for all parenteral pharmaceuticals and the normal procedure is to perform a pharmacopoeiasterility test on the product before it is released for use. However, since a sterility test takes two weeks and many radiopharmaceuticals have shelf-lives of only a few hours after preparation, it is normally just not possible to do a prospective sterility test on most radiopharmaceuticals before they are used.

However, this does not relieve the radiopharmacy from the need to ensure that their preparations are indeed sterile.

Confidence in the sterility of the product can be achieved by working in a clean environment and following a defined operating procedure which incorporates aseptic transfer techniques. This confidence can be endorsed by carrying out retrospective sterility tests on a sample of the radiopharmaceuticals prepared to ensure that they are indeed sterile.

In the UK, it is recommended to sterility test the generator eluate which remains un-used on the first and last days of the life of the generator as well as a variety of the different types of products prepared in the radiopharmacy.

How to perform sterility tests on radiopharmaceuticals

Labs are also encouraged to carry out process validation studies as a further test of both the environment and the individual operator's aseptic technique. These involve transferring nutrient broth using procedures which are identical to those normally used during radiopharmaceutical preparation. The broth is then incubated at 37 ° C for up to two weeks to allow any micro-organisms to grow. If the broth remains sterile at this time, then it provides good evidence that all is well.