Compounding pharmacies, veterinary clinics, and hospitals are tasked with preparing medications through a process that protects both the preparer and the patient. The United States Pharmacopeia (USP) sets quality standards for handling drugs. It specifies whether a formulation or procedure requires a sterile or non-sterile environment and whether the drug is hazardous. Publications such as USP <795> and USP <797> address compounding of non-hazardous drugs in non-sterile and sterile environments, respectively. USP <800> addresses the handling of hazardous drugs in both environments. It defines the engineering controls necessary to maintain the safety of individuals preparing these drugs for patient administration.
Medications that require sterile preparation are those introduced into a sterile area of the body. Examples include injections, infusions into the bloodstream or subcutaneous tissues, or ophthalmic solutions for the eye. Non-sterile medications include topical creams, gels, ointments, orally delivered tablets, suspensions, solutions, and lozenges. In these cases, some microbial contamination is permissible. Hazardous or potentially hazardous drugs can be formulated or processed in both sterile and non-sterile conditions. These drugs have at least one of six properties: carcinogenicity; teratogenicity or developmental toxicity; reproductive toxicity in humans; organ toxicity at low doses in humans or animals; genotoxicity; or a structure or toxicity comparable to a known hazardous drug. The National Institute for Occupational Safety and Health (NIOSH) recognizes three classes of hazardous drugs: antineoplastics (cancer-treating), non-antineoplastics (hazardous but not for cancer), and reproductive hazards only (drugs that pose risks to reproductive health). The type of containment indicated in the USP documents for these conditions depends in part on the preparation's phase and whether the drug is classified as hazardous. These documents refer to such devices as Containment-Primary Engineering Controls (C-PECs).
USP <795> does not require containment ventilated enclosures (CVEs) for non-sterile compounding; rather, a facility should assess particle-generating activities (e.g., weighing) to determine whether such a device is needed. In this context, a CVE is equivalent to a hood as it is distinguished from biological safety cabinets (BSCs). It is important to consider what non-sterile formulation is being prepared and whether it contains nonhazardous or hazardous drugs. For example, a topical analgesic gel preparation described in a US patent contains menthol, camphor, menthoxypropanediol, and aminomethyl propanol, which can cause eye and respiratory irritation but are not classified as hazardous drugs. The formulation contains a significant percentage of ethanol as well as other ingredients. Clearly, this should be prepared in a ductless hood equipped with HEPA and activated carbon filtration to protect the operator. The activated carbon filtration will remove irritating and hazardous chemical vapors, while the HEPA filter will remove any particles or aerosols generated by mixing and heating. Compositions involving strictly powders can be handled in a powder containment hood equipped with HEPA/ULPA filtration as another means of ensuring operator safety.
Processing a formulation in sterile conditions, as described in USP <797>, requires a C-PEC, such as a BSC Class II or III, to provide HEPA- or ULPA-filtered air to protect the drug from microbial contaminants and to protect the operator from exposure to the drug or excipients during processing. These cabinets provide the necessary ISO Class 5 environment for sterile processing. There are various subcategories of BSCs that provide distinct airflow configurations. In general, room air is drawn into a grille located just beyond the sash on the cabinet work surface and is HEPA-filtered before flowing downward into the cabinet chamber. This creates a buffer against incoming room air, helping to maintain sterility while directing harmful particulates away from the operator. Certain BSC configurations are hard ducted to exhaust air to the outside, while others recirculate the room air.
The compounding of hazardous drugs (HD) is governed by USP <800> for both non-sterile and sterile conditions. The standard distinguishes between C-PECs required for pre-sterilization procedures and those required for processes that must maintain sterility. For the former, a CVE or BSC Class I or II may be employed, provided the device is either equipped with redundant HEPA/ULPA filters in series or vented to the outside (preferred configuration). All sterile operations must be conducted in a C-PEC that delivers a minimum ISO Class 5 environment, such as a BSC Class II, and is required to be exhausted to the outside. An example of a sterile application performed within a BSC Class II device is the sterile filling of a designated HD, such as methotrexate, into an IV bag.
Mystaire supplies C-PEC products that address the needs of pharmacists, veterinarians, and clinicians for operator and medication protection, whether in a non-sterile or sterile processing environment, and whether involving nonhazardous or hazardous drugs. These solutions are designed to help facilities achieve and maintain compliance with USP standards while supporting safe and efficient compounding workflows.