The section in USP <797> addressing the requirements for radiopharmaceuticals as Compounded Sterile Preparations (CSPs) is based on specific and detailed recommendations from an advisory panel of nuclear pharmacists. This section clarifies details and exemptions for radiopharmaceutical compounding, especially in regards to microbial contamination risk levels.
Determining the risk level of CSPs prepared in a nuclear pharmacy is one of the most important aspects of the section. Keep in mind that both radionuclides and non-radioactive medications are handled, prepared, and stored in nuclear pharmacies. Table 1 provides a list of common radionuclides and traditional drugs that are prepared and dispensed with their corresponding risk levels.
Radiopharmaceuticals are not batched in the same way as traditional medications because of the half-life of the radionuclides. USP specifies that all drugs have 90% to 110% of their potency to still be stable. So if a drug is exposed to adverse conditions but still retains 90% to 110% of its potency it can be used. All radionuclides have specific half-lives that range from seconds to years. Technetium-99m has a half-life of six hours, meaning that the amount of the radioactive material will decrease by 50% every six hours. A 25-millicurie (mCi) dose of technetium-99m compounded at time zero will only be 12.5 mCi at six hours, 6.25 mCi at 12 hours, etc. Therefore, most radionuclides are prepared and administrated within 18 to 24 hours after compounding. Radiopharmaceuticals are prepared and handled as either single-dose containers or multipledose containers.
Radiopharmaceuticals compounded from sterile components in closed sterile containers and with a volume of 100 mL or less for a single-dose injection, or not more than 30 mL taken from a multiple-dose container, shall be designated as, and conform to, the standards for low-risk level CSPs.
This section in USP <797> requires low-risk CSPs to be prepared within an ISO Class 5 primary engineering control. Due to the inherent risks associated with handling radiopharmaceuticals, the ISO Class 5 environment used for aseptically compounded preparations can be a cleanroom, with its HEPA filters and low dust levels to achieve this environment. However, the cost of installing a cleanroom starting at $150/square foot, their cost can be prohibitively expensive. In addition, cleanrooms have high operating costs and take up valuable floor space.
As an alternative to cleanrooms, USP <797> specifically defines the use of a speciallydesigned, lead-lined, negative-pressure vertical airflow Compounding Aseptic Isolator (CAI). It is designed to maintain an aseptic compounding environment within the isolator through the compounding and material transfer processes. Air exchange into the isolator from the surrounding environment occurs through HEPA filters. Barrier isolators can take the place of a cleanroom by providing cleanroom conditions within a contained workspace. It provides the same level of air quality a cleanroom does, while taking up less space and being more cost-effective to operate. Isolators offer several advantages:
- Workers have no direct contact with the work area. The work area is accessed via a sealed
glove system. - Isolators take up far less valuable floor space than do cleanrooms.
- Workers do not have to fully gown before they begin work.
- Decontamination is easier in the small, contained environment of the isolator.
Although not all radiopharmaceuticals are classified as hazardous drugs, the engineering controls and work practices are intended to ensure the safety of the CSP as well as protect the operator from exposure to radioactivity.
References:
1. United States Pharmacopeial Convention. Chapter: Pharmaceutical Compounding Sterile Preparations. United
States Pharmacopeia 31/National Formulary 26. First Supplement Official Date, June 1, 2008.
2. Kara Duncan Weatherman, PharmD, BCNP and Eric S. Kastango, MBA, RPh, Addressing <797> Requirements for
Radiopharmaceuticals. http://www.pppmag.com/article_print.php?articleid=750 Accessed November 14, 2013.
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