Extemporaneous Compounding
- Compounding is a professional service that is unique to pharmacy
- The extemporaneous preparation and supply of a single ‘unit of issue’ of a therapeutic product intended for supply for a specific person in response to an identified need. (Source: Pharmacy Board of Australia, cited in APF25)
- Compounding is classified as “simple” or “complex”. All registered pharmacists must be competent at simple compounding.
Simple Compounding:
Is compounding formulas from official pharmacopoeias, formularies or other reputable references, excluding preparations that meet the definition of complex compounding. Complex compounding includes: sterile compounding, compounding of hazardous substances, capsules with >1 ingredient, tablets, troches, suppositories (see APF).
• Extemporaneously compounded preparations prepared in community or hospital pharmacy for an individual consumer are exempt from TGA registration but must meet acceptable professional practice standards.
• Pharmacy premises do not have to be TGA licensed or accredited under the Code of Good Manufacturing Practice for extemporaneous. compounding.
Documentation:
Risk assessment should be documented
Research and correspondence undertaken in the formulation of a non-standard preparation must be documented
Accurate details of the compounding process must be documented and approved by the pharmacist
Accuracy in Compounding:
- Compounding involves risk and utmost care must be taken to avoid errors.
- Compounding errors have led to patient deaths
- In 1998, a 4-day old baby was brain-damaged and subsequently died after being given an incorrectly compounded peppermint water preparation.
• Prepared by Pre-registration Student. - Used Concentrated chloroform water (10%) instead of Double-strength chloroform (0.5%) water ie 20 x the required amount.
• Stringent record-keeping and accuracy in calculations, measurements and techniques is essential for patient safety.
Risk Assessment:
Risk Assessment
• Two aspects:
Risk to patient
• Risk to staff and public
•Consider risks associated with:
Patient - dose, drug interactions, contraindications etc
Formulation - dosage form, complexity, compatibility, suitability
Premises and equipment
Personnel - training, safety
Regulations - legislation, scheduling, availability of suitable commercial preparation
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Why compound?
• Product must be freshly prepared
• Only compound if there is no alternative. If a comparable and suitable commercial preparation exists, then use that.
• Liquid formulation required and none exists commercially
• Patient has sensitivity to one of the excipients in commercial product
• Commercial product is not available or discontinued
• Product must be freshly prepared
Errors, Precision & Accuracy
Error - deviation of the observed from the true value.
systematic (determinate) arising from calibration mistakes, impurities etc).
additive (magnitude independent of sample size ie constant error)
• proportional (error changes with sample size ie incorrect stock solution strength).
• Precision - defined as standard deviation divided by the mean × 100 = %. May be referred to as the coefficient of variation. Little variation in repeat measurements.
• Accuracy - correct or truthful measurement. Accuracy and precision in compounding & dispensing are vital.
Accuracy in Weighing:
Accuracy in weighing is affected by:
•Environment
•Calibration
• Sensitivity/specification
Minimum weighable amount (United States Pharmacopeia) = 100mg
100mg + 1mg is the minimum weight that can be weighed on the electronic balance
•When weighing UP TO 500 mg - an allowance of ‡ 1% can be made when reading the weight e.g. (100 mg can be 99-101mg).
•Weights in EXCESS of 500 mg must have an allowance of no more than ‡ 5mg.
Accuracy in Measuring
• Do not measure a volume that is less than 20% of the total capacity of the measure.
• The minimum measurable volume using the equipment in the laboratory is therefore 0.2 mL (non-viscous liquids)
• When calculating volumes required, approximations of up to ‡ 1% may be made to allow more convenient measurements.
• Descending order of accuracy of measuring apparatus is: pipette (very accurate) burette cylinarical measure → conical measure=beaker (not accurate)
Accuracy of Measurement is affected by:
• Accuracy of measurement is affected by:
• Graduations on the measure
• Meniscus
• Alignment
• Transfer
• Selection of correct measure
Accuracy in Dispensing:
- Accuracy of weighing and measuring
• Methodical systems for dispensing (SOPs) inc dealing with interruptions
• Proper storage of medicines
• Methodical systems for checking
Product Quality and Pharmaceutical Elegance:
• Preparations should be pharmaceutically elegant
•Solutions should be sparkling clear, suspensions uniform and free of large particles, creams and ointments uniform and non-gritty.
• Pharmacopoeial grade ingredients are used, including sterile purified water, or sterile water for irrigation, non-sterile purified water must be freshly boiled and cooled via a validated process.
• Liquid preparations are subjected to clarification to achieve an elegant, safe product. Non-viscous solutions are made almost to volume and filtered through filter paper into a cylindrical measure. They are made to volume through the filter to achieve a clear, particle-free solution.
Clarification:
• Viscous solutions (rule of thumb: >40% syrup) filter too slowly, so should be strained. Two layers of gauze are placed between the two halves of a strainer. As the gauze retains little product the preparation can be made almost to volume in conical, strained into cylinder and made to volume through the strainer OR made to volume in a cylindrical measure and strained directly into the container.
• NOTE: allow sufficient drainage time for the viscous fluid to pass through the neck of the strainer.
• Suspensions and emulsions are 2 phase systems and cannot be filtered. These must be strained as per the viscous solutions.
