11 Chapter 11: Common Compounding Techniques
Pharmacy compounding involves precise techniques to ensure uniformity, stability, and accuracy in medications. It also ensures pharmaceutical elegance. Four essential methods—trituration, levigation, spatulation, and geometric dilution—are widely used for mixing, particle size reduction, and drug dispersion. Below is generalized information on these techniques.
Trituration
Trituration is the process of grinding, crushing, or pulverizing a substance into a fine powder using a mortar and pestle.
Purpose:
- Reduces particle size to improve drug uniformity.
- Ensures even mixing of powders and suspensions.
- Used for geometric dilution when blending potent drugs.
Use: Used when a fine powder is needed, such as in capsules or when a drug needs to be incorporated into a cream or ointment.
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Levigation
Levigation reduces particle size by grinding or triturating a solid powder with a liquid (levigating agent) to create a smooth paste before incorporating it into a semi-solid base (e.g., ointments, pastes). This can be done in a mortar and pestle or on a slab using a large stainless steel spatula.
Purpose:
- Reduces grittiness in topical preparations.
- Improves dispersion of insoluble powders in creams, pastes, and ointments.
- Enhances drug absorption by increasing surface area.
- Goal is a uniform, smooth and streak free product.
Common Levigating Agents:
- Mineral oil – Used for oleaginous bases (e.g., petrolatum-based ointments).
- Glycerin – Used for water-based preparations (e.g., creams and pastes).
Use: To form a smooth paste by triturating a solid with a small amount of levigating agent. Used primarily in the preparation of ointments, creams, and suspensions, and when incorporating insoluble powders into ointment or cream bases. eg. levigating zinc oxide with glycerin before mixing into a cream.
Spatulation
Spatulation is a mixing technique where ingredients are mixed on an ointment slab or tile using a spatula without applying pressure. Unlike trituration, spatulation does not reduce particle size—it is only for gentle mixing. Ensures uniform distribution of ingredients
Purpose:
- Maintains light, airy texture of creams and ointments.
- Prevents entrapment of air in emulsions.
- Ideal for soft, delicate powders or creams.
Use: Used when incorporating liquids into semi-solids (creams and ointments) and ideal for combining semi-solids such as ointments and creams.
Geometric Dilution
Geometric dilution is a series of dilution steps used to combine two or more ingredients of varying quantities together to achieve a homogeneous and uniform mixture (can be used to mix various dosage forms together such as powders, creams or ointments). Starting with the ingredients of the smallest amount (typically the active ingredient) and doubling the portion by adding the additional ingredients (the diluent) in order of quantity. Each addition should result in a doubled amount until all the ingredients are mixed in. The process of gradually diluting the active ingredient ensures even distribution of the active ingredient throughout the final product.
Purpose:
- Ensures uniform dispersion of API
- Prevents hot spots of concentrated API
- Essential when compounding low dose or high potency compounds
Technique:
- Start with the ingredients of the smallest amount (typically the active ingredient)
- Add an equal amount of the diluent
- Mix thoroughly until uniform
- Add an equal amount of the base again and mix
- Repeat this process until all of the base has been incorporated
Watch Video:
https://online.saskpolytech.ca/d2l/le/content/314498/viewContent/12733172/View
Use: Incorporating a small amount of API such as a powder into a large amount of semi-solid (such as ointment or cream) base. Diluting a high-potency API (for example estradiol into a diluent powder (e.g., lactose) before incorporating into a capsule or semi-solid. Used in the initial stages of making a suspension when combining a powder with a vehicle to make an initial paste or pourable liquid.
Comparison of techniques:
| Technique | Purpose | Used In | Key Consideration |
| Trituration | Reduces particle size | Powders, suspensions, capsules | Uses mortar & pestle |
| Levigation | Smooths powders for semi-solids | Ointments, creams, pastes | Uses a levigating agent |
| Spatulation | Gently mixes without compacting | Soft powders, creams, ointments | Done on an ointment slab |
| Geometric Dilution | Ensures uniform drug dispersion | Potent drug mixtures, powders, creams | Gradual stepwise mixing |
Manually Packing an Ointment Jar
- Fill bottom of jar
- Fill along sides of jar and remove air pockets that form (tap lightly on firm surface; not direct on counter)
- Depress spatula toward center and rotate jar to give product a smooth, professionally finished look
- Clean inside top edge & threads of jar with tissue
- Place lid on jar
