2.1 Facilities, Environmental Controls, and Equipment
Key Takeaways
- USP <795> requires a visibly designated, clean and orderly compounding space, but ordinary nonhazardous compounding does not require a permanently separate room.
- Nonsterile HD compounding under USP <800> requires a C-PEC in a C-SEC at 0.01–0.03 inch water column negative pressure, at least 12 ACPH, and external room exhaust; HEPA filtration of room exhaust is not required.
- Temperature, humidity, monitoring frequency, and device calibration must protect labeled conditions and follow manufacturer instructions, risk, and facility SOPs rather than invented universal schedules.
- When a 5% maximum error is specified, MWQ = sensitivity requirement / 0.05; an SR of 6 mg therefore yields 120 mg.
- Choose, clean, maintain, and verify equipment according to material properties, intended accuracy, manufacturer instructions, and the master formulation.
2.1 Facilities, Environmental Controls, and Equipment
Quick Answer: USP <795> requires a specifically designated, clean, orderly compounding space with a visible perimeter and suitable washable work surfaces; it does not require a separate room for ordinary nonhazardous compounding. Nonsterile hazardous-drug compounding under USP <800> uses a C-PEC in a negative-pressure C-SEC maintained at 0.01–0.03 inch water column negative pressure, at least 12 air changes per hour, and external exhaust. Select and verify measuring equipment against the formulation, manufacturer instructions, and facility SOPs.
Facility Design Standards under USP <795>
The primary objective of facility design under USP Chapter <795> (Pharmaceutical Compounding — Nonsterile Preparations) is to protect compounded nonsterile preparations (CNSPs) from cross-contamination, microbial proliferation, and physical or chemical degradation while ensuring operator safety.
USP <795> requires a specifically designated space with a visible perimeter. A separate or permanently dedicated room is not required for ordinary nonhazardous compounding. Other activities may occur in that space only when compounding is not taking place; during compounding, control traffic, interruptions, and cross-contamination.
Work Surface & Infrastructure Parameters
- Surface Construction: Work surfaces used for compounding must be cleanable, nonporous, and compatible with the cleaning agents and materials used. The designated space and nearby storage must support orderly cleaning and prevent contamination.
- Lighting & Space: Ample, shadow-free lighting is essential to facilitate precise measurement, visual inspection of powders, and accurate reading of meniscus lines on volumetric glassware. Space must be sufficient to allow orderly placement of balances, equipment, raw material containers, and documentation logs without crowding.
- Plumbing & Water Supply: Handwashing and equipment-cleaning facilities must be readily accessible without creating splash or contamination hazards. Use the water quality specified by the formulation. USP <795> says purified, distilled, or reverse-osmosis water should be used for the final equipment rinse.
- Splash Controls: Locate sinks, drains, and water sources so splash cannot contaminate components, equipment, or CNSPs. USP <795> does not impose a universal one-meter separation for an ordinary nonsterile work surface.
Physical Segregation of Compounding Workflows
The degree of separation follows the hazard and process. Keep ordinary nonhazardous work within the visibly designated <795> perimeter; hazardous-drug work requires the engineering controls in <800>:
| Compounding Category | Facility Separation Requirement | Key Risk Mitigated |
|---|---|---|
| Nonsterile Non-Hazardous | Visibly designated <795> space; not necessarily a separate room | Traffic, interruptions, and cross-contamination |
| Nonsterile Hazardous (USP <800>) | Dedicated, physically separate negative-pressure containment room (C-SEC) | Airborne hazardous drug residue and occupational exposure |
| Sterile Compounding (USP <797>) | Controlled cleanroom suite (ISO Class 7/8) or Segregated Compounding Area (SCA) | Microbial contamination and particulate entry |
Environmental Controls: Temperature, Humidity, and Monitoring
Environmental conditions directly impact raw component stability, powder flow characteristics, chemical oxidation rates, and microbial growth. Environmental conditions must remain suitable for the components, CNSP, equipment, and labeled storage. Monitoring method and frequency derive from manufacturer instructions, the master formulation, risk, and facility SOPs; <795> does not impose one universal continuous-monitoring schedule.
Storage Temperature Definitions (USP <659>)
All raw ingredients, active pharmaceutical ingredients (APIs), excipients, and finished CNSPs must be stored according to official USP temperature parameters:
- Freezer: Maintained between -25°C and -10°C (-13°F and 14°F). Used for temperature-sensitive APIs or specialized frozen formulations.
- Refrigerator: Maintained between 2°C and 8°C (36°F and 46°F). Required for aqueous oral suspensions, heat-labile biologics, or specific thermolabile semisolids.
- Controlled Room Temperature (CRT): Maintained between 20°C and 25°C (68°F and 77°F), with temporary excursions permitted between 15°C and 30°C (59°F and 86°F) experienced in pharmacies.
Relative Humidity Controls
Humidity must be controlled when it can affect material quality or handling. Hygroscopic powders can clump or change mass, while very dry air can increase static. The acceptable range comes from component specifications and the validated process, not a universal <60% RH limit in <795>.
Environmental Monitoring Protocols
- Storage monitoring: Monitor rooms, refrigerators, and freezers often enough to detect excursions and protect labeled conditions.
- Excursion review: Document out-of-range conditions and assess affected components or CNSPs before use or release.
- Device control: Verify or calibrate monitoring devices at the manufacturer- and SOP-defined interval using standards appropriate to the intended accuracy.
Containment Controls for Hazardous Nonsterile Compounding (USP <800>)
When nonsterile compounding involves any agent listed on the National Institute for Occupational Safety and Health (NIOSH) List of Antineoplastic and Other Hazardous Drugs, facilities must comply concurrently with USP Chapter <800>.
Primary Engineering Controls (C-PECs)
Nonsterile hazardous drug compounding must be performed within a Containment Primary Engineering Control (C-PEC) designed to capture airborne powders, aerosols, and vapors:
- Containment Ventilated Enclosure (CVE): Commonly referred to as a "powder hood," a CVE is a ventilated cabinet equipped with HEPA filtration that draws air away from the operator.
- Class I Biological Safety Cabinet (BSC): Protects personnel and environment by drawing room air through the work surface and filtering exhaust air through HEPA filters.
- Class II Biological Safety Cabinet (BSC): Provides both personnel protection and product protection via laminar HEPA-filtered airflow.
Secondary Engineering Controls (C-SECs)
The room housing the nonsterile C-PEC is designated as the Containment Secondary Engineering Control (C-SEC). USP <800> mandates that the nonsterile C-SEC must be:
- Physically Separate: A distinct, enclosed room dedicated exclusively to hazardous drug handling.
- Negative Pressure: Maintained under negative pressure relative to all adjacent areas, with a differential pressure of -0.010 to -0.030 inches of water column (-2.5 to -7.5 Pascals). This negative pressure gradient prevents hazardous dusts from escaping into adjacent non-hazardous pharmacy spaces.
- Air Change Rate: Engineered with a minimum air change rate of at least 12 Air Changes Per Hour (ACPH).
- External Venting: The nonsterile C-SEC is externally vented; USP <800> does not require HEPA filtration of the room exhaust. The nonsterile C-PEC is preferably externally vented, with the chapter-specified redundant HEPA alternative when used.
Compounding Equipment & Measurement Mechanics
Accurate measurement of mass and volume is fundamental to nonsterile compounding. Technicians must understand balance mechanics, volumetric rules, and equipment selection criteria.
Prescription Balances: Class III (Class A) Torsion Balance vs Digital Electronic Balance
Traditionally, pharmacies utilized a Class III (Class A) Torsion Prescription Balance, which relies on internal weights and mechanical arms. Today, most modern compounding laboratories use digital electronic analytical balances. However, PTCB exam standards heavily test the fundamental mathematical mechanics governing mechanical Class III balances.
Sensitivity Requirement (SR) & Minimum Weighable Quantity (MWQ)
The Sensitivity Requirement (SR) is the maximum weight required to move the balance pointer by one mark on the index plate. For a standard Class III torsion balance, the SR is 6 mg.
When the formulation or facility procedure selects a 5% maximum weighing error, the traditional calculation determines the Minimum Weighable Quantity (MWQ). The tolerance comes from the master formulation, equipment capability, and SOP; it is not a universal release specification for every CNSP.
MWQ Formula:
MWQ = Sensitivity Requirement (SR) / Desired Accuracy (Maximum Allowable Error Rate)
Worked Example 1: Standard MWQ Calculation
- Given: A Class III prescription balance has a Sensitivity Requirement (SR) of 6 mg. The allowable error limit is 5% (0.05).
- Calculation: MWQ = 6 mg / 0.05 = 120 mg
- Interpretation: On this Class III balance, a technician can NEVER weigh a mass smaller than 120 mg directly. Weighing any quantity below 120 mg will result in a percentage error greater than 5%.
Worked Example 2: Percentage Error Calculation
- Problem: A technician attempts to weigh 40 mg of an API directly on a balance with an SR of 6 mg. What is the percentage error?
- Formula: Percentage Error = (Sensitivity Requirement / Target Weight) * 100%
- Calculation: Percentage Error = (6 mg / 40 mg) * 100% = 15%
- Conclusion: A 15% error violates the 5% USP threshold. To obtain 40 mg of active drug accurately, the technician must perform an aliquot dilution method using an inert diluent (such as lactose or microcrystalline cellulose).
Volumetric Glassware and Measurement Rules
| Equipment Type | Description & Primary Use | Measurement Accuracy & Rules |
|---|---|---|
| Cylindrical Graduate | Uniform vertical cylinder with linear volume graduations | High accuracy; preferred for precise volume measurement |
| Conical Graduate | Cone-shaped vessel with wider top and narrower base | Lower accuracy; easier for stirring and mixing liquids |
| Volumetric Flask | Flat-bottomed bulb with narrow neck and single calibration line | Highest accuracy; used for preparing exact volumetric solutions |
| Oral Syringes | Calibrated plastic syringes without needle luer threads | High accuracy for small volumes (< 10 mL); eliminates meniscus error |
| Pipettes / Micropipettes | Narrow calibrated tubes for micro-liter or sub-milliliter delivery | Essential for potent liquid APIs and low-volume liquids |
The 20% Rule of Volumetric Measurement
To maintain volumetric accuracy, a technician should never measure a liquid volume that is less than 20% of the graduate's total rated capacity.
- Example: In a 100 mL cylindrical graduate, the minimum accurate volume that can be measured is 20 mL (100 mL * 0.20). Measuring 10 mL in a 100 mL graduate introduces significant meniscus reading errors. For a 10 mL target, a 10 mL or 25 mL graduate must be selected.
Mixing and Comminution Equipment Selection
Selecting the correct mortar, pestle, and spatula material depends on the chemical properties of the drug:
- Glass Mortar & Pestle: Smooth, non-porous glass surface. Ideal for preparing liquid solutions, suspensions, mixing oils, or triturating volatile, staining, or oily substances (e.g., iodine, coal tar, synthetic dyes). Easily washed and sterilized; does not absorb chemicals.
- Porcelain Mortar & Pestle: Glazed exterior with a slightly roughened interior surface. Excellent for general powder blending, triturating soft aggregates, and reducing particle size of soft tablets.
- Wedgwood Mortar & Pestle: Unglazed, porous ceramic surface with high abrasive quality. Best suited for fine trituration of hard crystals and gritty powders. Note: Wedgwood absorbs liquid and staining chemicals easily; must be washed thoroughly and dried completely.
- Spatula Selection:
- Stainless Steel Spatulas: Rigid and durable; used for general powder transferring and ointment mixing. Contraindication: Cannot be used with corrosive chemicals or metallic ions (e.g., iodine, mercury, potassium iodide, phenol) which react with metals.
- Hard Rubber or Plastic Spatulas: Flexible and non-reactive; mandatory when handling chemicals that corrode metal.
- Ointment Slabs & Parchment Pads: Ground glass slabs or silicone-coated parchment paper pads used for spatulation and levigation of topical semisolids.
- Mechanical Equipment:
- Ointment Mill: Passes coarse ointments through precision rollers to reduce particle size and eliminate grittiness.
- Electronic Mortar and Pestle (Unguator): Closed-system mixer that homogenizes creams and ointments directly inside the final dispensing jar, minimizing air entrapment and cross-contamination.
Equipment Cleaning, Sanitization, and Maintenance Logs
Equipment must be cleaned immediately after use to prevent cross-contamination between batches.
Hazardous-Drug Equipment Surface Sequence (USP <800>)
Use agents compatible with the HD and equipment for deactivation, decontamination, and cleaning. Disinfection is added when sterile compounding requires microbial control; it is not a universal fourth step for nonsterile HD equipment.
Equipment Maintenance Records
Document the equipment ID, verification or maintenance performed, result, person/date, deviations, and return-to-service decision as required by the equipment program and facility SOP. Retain records for the period required by applicable law and policy; USP <795> does not create a universal two-year rule.
A technician is using a Class III prescription balance with a Sensitivity Requirement (SR) of 6 mg. What is the Minimum Weighable Quantity (MWQ) to ensure a percentage error no greater than 5%?
Which type of mortar and pestle is best suited for triturating a volatile, dark-staining chemical such as iodine into a liquid preparation?
Under USP <800>, what are the mandatory room pressure and air change requirements for a nonsterile hazardous drug Containment Secondary Engineering Control (C-SEC)?
According to volumetric measurement rules in compounding, what is the minimum volume of liquid that should be measured in a 50 mL cylindrical graduate?