Cross contamination in pharmacies
04/01/2001
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by Hank Rahe
The preparation and delivery of the final drug substance either in the retail pharmacy or hospital setting is an area of increasing concern. The patient final dosage in all cases exceeds the "no effect" level for the compound. Exposure to multiple doses such as in the dispensing of tablets of a given compound or preparation of a number injectable products without proper protection can result in exceeding the exposure limit.
Casual contact by nurses delivering, administrating or checking products at the patient bedside can exceed the exposure limits for low-exposure-level products such as cytotoxics. Recent tests have shown that the simple act of adding an active drug substance to a 100 ml plastic bag for infusion into a patient in the hospital pharmacy can generate more than a microgram of airborne drug substance. This exceeds the "no effect" level of most cytotoxic drugs available today.
The same testing showed that administration by nurses through IV sets by syringe or 100-ml plastic bag creates airborne contamination in the same concentration range. Both pharmacists and nurses are in a workplace setting where this is a routine operation and, without proper containment devices in place, are put at great risk.
Reducing this risk of exposure requires the use of proper engineering control technology. Selection of the proper technology is critical. Many of the choices available include equipment that was developed for different applications and transferred for use in the pharmacy. This equipment is based on safety data that was developed for a different purpose. An example is the use of the Class II biological safety cabinet that has been tested and pronounced safe based on containment of biological markers in a static state. Actual use of the device in the pharmacy involves dynamic activities and multiple movement of materials into and out of the controlled environment of the biological safety cabinet, thereby creating an entirely different situation from the one in which the cabinet was tested.
In the retail setting the counter where the pharmacist prepares the individual prescriptions is often an open environment where customers can come in contact with airborne contamination.
Many pharmacies use either counting trays or automatic counters to count out the tablets and capsules. These devices, if not properly cleaned between each product, can cross contaminate other prescriptions.
This is not a problem except when the cross contamination is a highly potent compound. An example would be an antibiotic cross contaminating another product given to someone with an allergy to the antibiotic. The level of contamination needs only to be in the microgram range for this to result in serious repercussions for the individual.
Tablets and capsules are often treated as if they are closed containers of the active drug substance, which is not true in the majority of cases. Both tablets and capsules can, and do, generate airborne contamination as they are dispensed. It is highly likely that in the transport of these materials from manufacturing site to distribution location, and ultimately to the pharmacy in which they are dispensed, the product will log a considerable number of road miles.
During this travel the products, no matter how well packaged, will have some level of movement that will cause them to generate particles of active drug substance. In extreme cases this can be seen as powder in the bottom of the bottle.
The dust containing the active drug substance becomes airborne by pouring the tablets or capsules onto the counting plate or into and out of the automatic counting devices. From this point it travels by air or contact surface to an unsuspecting person. The pharmacist is at greatest risk but individuals at or near the pharmacy counter can also be at risk. Proper containment needs to be applied in these areas as well as the hospital settings.
Hank Rahe is director of technology at Contain-Tech in Indianapolis. He is the past chairman of the board of the International Society of Pharmaceutical Engineers, and is a member of the CleanRooms Editorial Advisory Board.