Articles

Monitoring aseptic units — a microbiology audit tool

By Robert Lowe, BPharm, MRPharmS

Pharmacy aseptic units should monitor the quality of services provided to them by external suppliers. This article describes an audit tool developed by one hospital manufacturing unit that has been used to confirm the reliability of environmental monitoring carried out by an external laboratory

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Robert Lowe is acting director of quality assurance specialist services at the NHS Pharmacy Practice Unit based at the University of East Anglia

The environment where an aseptic product is prepared

The environment in which an aseptic product is prepared is critical to the quality of the finished product

SUMMARY

Aseptic preparation of medicines in hospital pharmacy units usually comprises the combination of licensed sterile ingredients in a manner that will ensure that the resulting product, in its final container, is sterile. One of the inherent weaknesses of this activity is that aseptically prepared medicinal products cannot be tested for sterility as would normally be the case for other sterile manufactured medicines.

There are two reasons for this. First, such preparations are usually prepared as single items for individual patients. If the product were to be subjected to the pharmacopoeial test for sterility there would be no medicine left to administer to the patient.

Second, and perhaps less obviously, a sample for sterility testing cannot be taken without compromising the integrity of the final container (eg, the syringe) thereby exposing the remainder of the medicine to possible microbial contamination.

The pharmacist responsible for releasing the medicine therefore relies upon the overarching quality assurance systems in place to ensure that the medicine is sterile. Good quality assurance systems include appropriately trained staff working in accordance with validated procedures, using tested and calibrated equipment, and undertaking aseptic preparation in a clean environment that is routinely monitored.

Standards have been set for the microbiological cleanliness of the immediate (and background) environment in which the manipulation of aseptically prepared medicines occurs. The maintenance of a suitably clean working environment is assessed via a programme of routine environmental monitoring of both physical and microbiological parameters. The minimum frequencies for such monitoring have been established for the NHS.