8.2 Sterile Compounding (USP <797>): Cleanrooms, ISO Classifications & Aseptic Protocols

Sterile Compounding and USP <797>

USP <797> establishes minimum standards for compounded sterile preparations (CSPs). The revised chapter effective November 1, 2023 uses Category 1, Category 2, and Category 3, not the former low-, medium-, and high-risk levels. Mississippi Article XXVIII and applicable USP adoption make current sterile standards central to pharmacy operation.

Categories and BUD

A Category 1 CSP is prepared in a suitable primary engineering control located in a segregated compounding area and has a maximum BUD of 12 hours at controlled room temperature or 24 hours refrigerated. This short BUD reflects the less controlled surrounding environment.

A Category 2 CSP is prepared in a cleanroom suite and may receive longer BUDs only when the preparation method, sterility approach, storage, container, and testing meet the applicable tables. A Category 3 CSP may receive still longer BUDs but requires the chapter’s additional personnel, environmental, formulation, sterility, stability, and frequency conditions. Do not memorize one maximum independent of terminal sterilization, aseptic processing, sterility testing, endotoxin testing, and storage.

An immediate-use CSP has a narrow emergency or immediate-administration pathway and administration must begin within the current chapter’s time limit from the start of preparation. It does not authorize routine advance batching or storage.

Engineering controls and pressure

The primary engineering control provides ISO Class 5 conditions at critical sites. For nonhazardous compounding in a cleanroom suite, the buffer room is positive to adjacent less-clean areas and maintains at least the current chapter’s minimum pressure differential—commonly expressed as at least 0.020 inch water column. Teach the minimum rather than inventing an upper “legal range.”

Hazardous sterile compounding follows USP <800> containment, including externally vented containment engineering control and negative-pressure room relationships. A positive nonhazardous room and a negative hazardous room serve opposite contamination-control purposes.

Certification occurs initially and at least every six months and after relevant changes or failures. Air and surface monitoring, pressure and temperature review, cleaning, disinfecting, and investigations demonstrate continuing control.

Personnel qualification

Personnel complete didactic and practical training, hand hygiene and garbing assessment, gloved fingertip and thumb sampling, and media-fill testing at the frequency required for their assigned category and work. A successful annual course alone does not replace observed aseptic qualification.

Garbing follows the required order and excludes jewelry, cosmetics, and items that compromise control. Sterile gloves are disinfected frequently with sterile 70% IPA. Critical sites remain in first air and are not blocked by hands, supplies, or equipment.

Preparation and release

The master formulation and compounding record identify ingredients, lot numbers, calculations, sterilization and filters where used, equipment, personnel, preparation time, BUD, storage, quality tests, and final inspection. Sterilizing-grade filters require integrity testing where applicable. Terminal sterilization is preferred when formulation and container permit.

Before release, inspect for particulates, discoloration, leaks, container integrity, label accuracy, and reconciliation. A preparation that fails sterility, endotoxin, environmental, or integrity criteria remains quarantined and is investigated.

Exam method

Identify immediate use or Category 1–3, environment, sterilization method, testing, and storage before selecting a BUD. Remember Category 1 = 12 hours room / 24 hours refrigerated. For pressure, distinguish positive nonhazardous protection from negative hazardous containment and use the current minimum.

Category comparison example

A CSP prepared in an ISO Class 5 hood placed in a compliant segregated compounding area is Category 1 and uses the 12-hour room or 24-hour refrigerated maximum even if the compounder has years of experience. Moving the same hood into a certified cleanroom suite does not automatically justify every Category 2 BUD; sterilization method, testing, package, and storage table still control.

If a nonhazardous buffer room loses positive pressure, stop and assess affected operations under the quality system. For a hazardous antineoplastic, using that positive room would reverse containment intent; the <800> negative-pressure suite and externally vented C-PEC are required. Record excursion, investigation, affected CSP disposition, correction, recertification when indicated, and resumption decision.

A BUD is assigned only after all release conditions are met. If environmental monitoring, filter-integrity testing, sterility testing, or endotoxin testing required for the intended category is pending or fails, keep the preparation quarantined and investigate.

Contamination-control example

A compounder reaches behind supplies and blocks first air to a vial stopper. Even if the room and hood certify correctly, that manipulation compromises aseptic technique. Stop, replace or disinfect affected materials as the procedure requires, and assess the CSP rather than assuming the HEPA filter corrects every movement. Trend media-fill, fingertip, surface, and air results together; repeated low-level recoveries can reveal a process failure before a sterility test becomes positive.