USP 797 is a set of national standards that governs how pharmacies and healthcare facilities prepare sterile medications, such as IV bags, injectable drugs, and eye drops. Published by the United States Pharmacopeia (USP), it exists to prevent contamination, infection, and patient harm whenever a medication is compounded in a sterile environment. The most recent revision was published on November 1, 2022, with an official effective date of November 1, 2023, after a one-year implementation period.
If a medication enters the body through injection, infusion, or the eyes, even trace amounts of bacteria or particulate matter can cause serious harm. USP 797 spells out exactly how facilities must design their rooms, train their staff, monitor their air quality, and assign expiration dates to keep that from happening.
Who USP 797 Applies To
Any facility that compounds sterile preparations (CSPs) falls under USP 797. That includes hospital pharmacies mixing IV medications, outpatient infusion centers, compounding pharmacies preparing custom injections, and even ophthalmology clinics making sterile eye solutions. State boards of pharmacy typically enforce compliance, and accreditation organizations like The Joint Commission reference USP 797 during inspections.
The Three CSP Categories
USP 797 organizes compounded sterile preparations into three categories. The category a preparation falls into depends primarily on the environment where it’s made, the level of protective garbing worn by personnel, how frequently the facility tests its environment, and how long the preparation is intended to last before use.
All three categories can involve sterile starting ingredients, nonsterile starting ingredients, or a combination of both. What changes between categories is the rigor of safeguards and the shelf life (called the “beyond-use date,” or BUD) that the facility is allowed to assign.
Category 1
Category 1 covers preparations with the shortest shelf life: up to 12 hours at room temperature or up to 24 hours refrigerated. Because these preparations are used quickly, the requirements are the least intensive of the three categories. Sterility testing is not required. Facilities must perform viable air sampling at least every 6 months and surface sampling at least monthly. Gowns can be reused within the same shift by the same person, as long as the gown stays in or near the classified compounding area.
Category 2
Category 2 allows longer shelf lives and requires a more controlled environment to match. When made from only sterile starting ingredients (without sterility testing), a Category 2 CSP can be assigned up to 4 days at room temperature, 10 days refrigerated, or 45 days frozen. If any nonsterile starting ingredients are used, those limits drop to 1 day at room temperature, 4 days refrigerated, or 45 days frozen.
To qualify for Category 2 BUDs, the compounding equipment must be placed in an ISO Class 7 buffer room within a full cleanroom suite. An alternative option allows a pharmaceutical isolator to be placed in an ISO Class 8 environment without requiring a separate anteroom. Sterility testing may be required depending on the BUD assigned. Air sampling and surface sampling follow the same schedule as Category 1: every 6 months and monthly, respectively.
Category 3
Category 3 is the most demanding tier, reserved for preparations that need the longest shelf lives. Sterility testing is required for every batch. Viable air sampling must happen at least monthly and must also be completed within 30 days before any Category 3 compounding begins. Surface sampling increases to at least weekly.
Garbing requirements are significantly stricter. No skin can be exposed, meaning the face and neck must be covered. All outer garments must be sterile and low-lint. Disposable garbing items cannot be reused at all, and laundered garments must be re-sterilized through a validated cycle before wearing again. Facilities must also have documented procedures for disinfecting any reusable equipment like goggles or respirators.
Cleanroom Design and Air Quality
USP 797 requires facilities to maintain specific levels of air cleanliness, measured by ISO classifications. ISO classes rate rooms by how many airborne particles are present per cubic meter, with lower numbers indicating cleaner air. The actual compounding work surface (inside a laminar airflow workbench or isolator) must meet ISO Class 5, the cleanest standard used in pharmacy compounding. The surrounding buffer room where compounding equipment sits typically must meet ISO Class 7, while the anteroom, where staff change into cleanroom garb, generally must meet ISO Class 7 or 8 depending on the facility’s configuration.
Positive air pressure differentials between rooms prevent contaminated air from flowing into cleaner spaces. The buffer room maintains higher pressure than the anteroom, which maintains higher pressure than the general environment outside. Facilities that handle hazardous drugs follow different pressure rules to contain toxic particles rather than exclude contaminants.
Cleaning and Disinfection Rules
All cleaning, disinfecting, and sporicidal agents used inside the primary compounding equipment must be sterile. When concentrated agents need diluting for use in that space, sterile water is required. Cleaning supplies like wipers, sponges, and mop heads must be low-lint and should be disposable. If reusable cleaning tools are necessary, they must stay dedicated to the classified area and be made of non-porous, cleanable materials. Wood and other porous materials are not allowed.
The standard breaks cleaning responsibilities into three distinct activities: general cleaning, disinfecting, and applying sporicidal agents. Each has its own minimum frequency that scales with the CSP category being compounded. The frequency of sporicidal application is actually one of the factors that determines which category a facility can compound under.
Beyond-Use Dating
One of the most practical elements of USP 797 is its limits on how long a compounded sterile preparation can be stored before it must be discarded. These beyond-use dates exist because compounded medications lack the extensive stability testing that commercially manufactured drugs undergo. The BUD acts as a safety window: the preparation must be used or thrown away before it expires.
Category 1 preparations have the tightest window, at just 12 hours at room temperature or 24 hours refrigerated. Category 2 preparations extend to days or weeks depending on storage conditions and whether nonsterile ingredients were used. Category 3 preparations, backed by mandatory sterility testing and the most stringent environmental controls, can be assigned the longest dates. In every case, the assigned BUD cannot exceed what the facility’s environmental monitoring data and sterility testing (when applicable) support.
Personnel Training and Competency
USP 797 requires that every person involved in sterile compounding demonstrate competency before working independently. Training covers aseptic technique (the practices that keep sterile products from becoming contaminated), proper hand hygiene, garbing procedures, and cleaning protocols. Personnel must pass competency assessments that include media-fill tests, where they simulate compounding using growth media instead of actual drugs. If bacteria grow in the media, the test reveals a break in technique.
Gloved fingertip and thumb sampling is another required competency check. After garbing, personnel press their gloved fingertips onto growth plates. Colony counts above established thresholds indicate the person’s technique needs correction before they’re cleared to compound. These assessments aren’t one-time events. Staff must requalify on a regular schedule to maintain their authorization to work in the cleanroom.
Why USP 797 Matters
Contaminated sterile preparations have caused real outbreaks. The most notable was the 2012 fungal meningitis outbreak linked to a compounding pharmacy in Massachusetts, which killed 64 people and sickened over 750. That tragedy accelerated both federal legislation (the Drug Quality and Security Act of 2013) and efforts to strengthen USP 797. The standard’s requirements for environmental monitoring, personnel testing, and strict expiration dating all work together to catch contamination before it reaches a patient. For anyone working in or receiving treatment from a compounding pharmacy, USP 797 is the baseline that separates safe practice from preventable risk.