3.2 Master Formulation Records, Compounding Procedures & Beyond-Use Dates

Master Formulation Records, Compounding Procedures & Beyond-Use Dates

Core Principle: Every compounded preparation must be safe, chemically stable, and completely reproducible. Under the NAPRA Model Standards, pharmacy technicians follow validated Master Formulation Records, execute meticulous physical compounding techniques, maintain detailed batch Compounding Records, and assign conservative Beyond-Use Dates (BUDs) to safeguard patient health.

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1. Master Formulation Record vs. Compounding Record

Compounding documentation is built upon two distinct, complementary records that provide a complete audit trail from formulation design to patient delivery.

Master Formulation Record (MFR) — The Recipe

The Master Formulation Record (MFR) is the authorized, master blueprint that provides the detailed instructions for preparing a specific compound before it is ever compounded for a patient. An MFR must be established and peer-reviewed by a pharmacist before any new formulation is compounded. It ensures that every future batch is prepared identically regardless of which pharmacy technician performs the compounding.

Mandatory Components of an MFR:

• Official Title & Description: Compound name, strength, and pharmaceutical dosage form.
• Ingredient Master Table: Exact chemical name, grade (USP, NF, BP, or analytical grade), and calculated quantity of every active pharmaceutical ingredient (API) and excipient required for a standard batch size.
• Equipment & Supplies: Specific compounding equipment needed (e.g., electronic balance, glass mortar, porcelain slab, specific mold sizes).
• Personal Protective Equipment (PPE): Required safety apparel (e.g., standard lab coat, nitrile gloves, or Level C chemotherapy PPE).
• Step-by-Step Procedure: Clear, chronological compounding instructions including comminution, levigating agent selection, order of mixing, mixing times, and temperature parameters.
• Quality Control Criteria: Measurable release specifications (e.g., physical appearance, color, clarity, pH range, weight variation limits, minimum and maximum theoretical yield).
• Packaging & Storage: Container-closure specifications (e.g., amber glass bottle, collapsible ointment tube, tight light-resistant container) and storage conditions (e.g., controlled room temperature, refrigerated 2°C to 8°C).
• Assigned Beyond-Use Date (BUD): Maximum allowable BUD justified by pharmacopeial monographs (USP <795>) or peer-reviewed, stability-indicating chemical assay literature citations.
• Sample Label Design: Standardized label layout including required auxiliary warning labels (e.g., "Shake Well Before Use", "Keep Refrigerated").

Compounding Record (CR) — The Batch Execution Log

The Compounding Record (CR), commonly called the compounding log, is the batch-specific document generated every single time a compound is prepared. It captures the real-time execution of the MFR for an individual prescription or batch.

Mandatory Components of a CR:

• Master Record Reference: Title and unique identifier of the MFR followed.
• Prescription & Batch ID: Patient prescription number or internal batch/lot number.
• Component Traceability: For every ingredient used: manufacturer, commercial lot number, and manufacturer expiration date.
• Actual Measurements: Actual measured weights or volumes of each ingredient, recorded alongside theoretical quantities.
• Yield Calculations: Theoretical yield vs. actual yield obtained, along with the calculated percentage yield: $\text{Percentage Yield} = (\text{Actual Yield} / \text{Theoretical Yield}) \times 100\%$.
• Quality Control Verification: Documented results of visual inspection, weight variation checks, and pH readings.
• Signatures & Accountability: Date and time of preparation, signature/initials of the compounding pharmacy technician, and signature of the verifying technician or pharmacist conducting final release.
• Assigned Batch BUD: Calculated Beyond-Use Date for that specific preparation.

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2. Fundamental Pharmaceutical Compounding Techniques

Mastery of physical compounding techniques ensures that active ingredients are uniformly dispersed and cosmetically elegant.

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A. Comminution & Trituration

• Comminution: The mechanical process of reducing the particle size of a solid substance. Smaller particles exhibit increased surface area, enhancing dissolution rates, reducing settling velocity in suspensions, and eliminating gritty textures in topical creams.
• Trituration: Continuous rubbing or grinding of a solid in a mortar with a pestle. Trituration reduces particle size while blending dry components.
• Pulverization by Intervention: Utilized for gummy, waxy, or hard crystalline substances that resist mechanical grinding (e.g., camphor, menthol, iodine). The solid is dissolved in a small volume of a volatile "intervening" solvent (such as 95% ethanol). The solution is triturated in a glass mortar; as the volatile solvent rapidly evaporates, the solute precipitates out as an impalpable, ultra-fine powder.

B. Levigation

Levigation is the process of reducing the particle size of a powder and dispersing it into a smooth paste by grinding it with a small amount of a viscous liquid (the levigating agent) in which the powder is insoluble. Levigation is performed on an ointment slab using a spatula or inside a glass mortar.

• Matching Polarity with the Base Vehicle:
  • Oleaginous / Hydrocarbon Bases (e.g., white petrolatum, Aquaphor, Plastibase) $\rightarrow$ Use mineral oil (light mineral oil) as the lipophilic levigating agent.
  • Water-Washable / Water-Soluble Bases (e.g., hydrophilic ointment, vanishing cream, Dermabase, polyethylene glycol [PEG] ointment, aqueous gels) $\rightarrow$ Use glycerin, propylene glycol, or purified water as the hydrophilic levigating agent.
• Quantity Rule: Use only the minimum volume of levigating agent required to wet the powder into a smooth paste (typically a 1:1 weight-to-volume ratio). Excessive liquid thins the ointment base, reducing viscosity and compromising topical adherence.

C. Geometric Dilution

Geometric dilution is the mandatory pharmaceutical method for blending two or more substances of unequal quantities to achieve absolute homogeneity. It prevents "hot spots" or uneven dosing when potent active drugs are diluted with large amounts of excipient or ointment base.

1. Place the smaller quantity of active drug on the slab or in the mortar.
2. Add an approximately equal volume of the diluent powder or base.
3. Triturate or spatulate thoroughly until the mixture is uniform.
4. Observe that the mixture volume has doubled. Add an amount of diluent equal to the current volume of the mixture.
5. Mix thoroughly until homogeneous.
6. Repeat this progressive doubling process until all diluent or base is incorporated.

D. Spatulation

The blending of powders or semisolids on an ointment slab or pad using a flexible spatula. Spatulation provides gentle mixing without significant particle size reduction. It is especially useful when incorporating heat-sensitive materials or blending powders that form eutectic mixtures (substances like camphor, menthol, and phenol that liquefy when triturated together; if a dry powder is desired, each ingredient must be triturated separately with an inert powder like magnesium oxide before gentle spatulation).

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3. Packaging & Container-Closure Selection

Packaging protects compounded preparations from environmental degradation throughout their shelf life:

• Amber Glass & Plastic Containers: Provide light-resistant barriers protecting photolabile drugs (e.g., nifedipine, hydrocortisone, tretinoin) from photochemical oxidation.
• Ointment Tubes vs. Ointment Jars: While wide-mouth plastic jars are common, collapsible metal or plastic ointment tubes are superior because they prevent patient fingers from introducing bacterial contamination into the remaining product and minimize exposure to atmospheric oxygen.
• Oral Dosing Syringes: Water-containing pediatric oral liquids must be dispensed with calibrated oral dosing syringes (and bottle adaptors) rather than household spoons, ensuring volumetric dosing accuracy.
• Child-Resistant Closures (CRCs): Provincial pharmacy standards generally require child-resistant packaging for dispensed medications unless the patient or prescriber asks for an easy-open container.

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4. Beyond-Use Date (BUD) Determination

A Beyond-Use Date (BUD) is the date after which a compounded preparation should no longer be used. NAPRA's non-sterile guidance (Table 4, adapted from USP <795>) gives maximum BUDs for preparations in air-tight, light-resistant containers when no specific stability data exist. The manufacturer's expiry date of an ingredient must not be used as the BUD of the final preparation.

Note on USP: The United States revised USP <795> in 2023 with different default BUDs. Canadian practice follows NAPRA's standards as adopted by each province, so learn the NAPRA table below for the PEBC exam.

The Absolute Expiration Ceiling

The assigned BUD can never exceed the earliest manufacturer expiration date of any raw ingredient, active drug, or commercial vehicle used in the compound. If a non-aqueous capsule has an allowable 6-month BUD, but the bulk active drug expires in 45 days, the assigned BUD must be capped at 45 days.

Standard Default BUD Matrix (in the Absence of Published Stability Data)

When specific, published stability-indicating analytical studies do not exist for the exact formulation, vehicle, and container, pharmacy technicians must assign default conservative BUDs based on aqueous content and route of administration:

Extended BUD Exceptions

A BUD may exceed the default matrix limits only when supported by valid, peer-reviewed, stability-indicating chemical assay studies published in reputable pharmaceutical literature (e.g., International Journal of Pharmaceutical Compounding, USP-NF monographs, SickKids Hospital formulas) that evaluated the identical active drug concentration, vehicle, pH, preservative system, and storage container.