Lecture 33: Compounding Suspensions

What is a dispersion?

A 2-phase system, where one phase is distributed as particles (varied sizes) into another phase

What is the dispersed phase?

Internal phase

What is the continuous phase?

External phase = dispersion medium

What is the product w/ solid dispersed phase & liquid continuous phase?

Suspension

What is the product w/ liquid dispersed phase & liquid continuous phase?

Emulsion

What does a suspension contain?

1. External phase (continuous phase) that is liquid

2. Internal/dispersed phase that is particulate solid matter

What are nonsterile suspensions?

• Topical & cosmetic

• Oral

• Otic

• Rectal

What are sterile suspensions?

• Inhalation

• Ophthalmic

• Injectable

What are suspensions < 1 micrometer (colloidal)?

Nanosized suspensions

What are suspensions > 1 micrometer?

Macrosized suspensions

Why compound suspensions?

Appropriate when the drug to be incorporated is not sufficiently soluble or chemically stable in a solvent

What is wettability of a suspended solid?

Wettability is the ability of liquid to adhere or spread across a solid surface

What important considerations for formulating suspensions?

1. Wettability of suspended solid

2. Size of suspended particles

3. Viscosity

What is viscosity?

Comprised of desirable properties such as:

• Syringability

• Spreadability

• Pourability

How to induce flocculation?

1. Reduce electrostatic potential

2. Sterically

What are deflocculated suspensions?

• High viscosity in the external phase slows down the sedimentation

• Sedimentation is very slow, but once formed, sediment is hard to resuspend

What are flocculated suspensions?

• Particles form loose aggregate- flocs (induced by electrical charge shifts or adding polymers/surfactants)

• Sediment forms quickly, but it is loose & can be resuspended by shaking

What are ingredients in compounded suspensions?

• Wetting agents

• Viscosity-increasing agents

• Suspending agents

• Vehicles

• Auxiliary agents

What is trituration?

Decreasing particle size of powders by grinding them in the mortar w/ a pestle

What is levigation?

Decreasing particle size of powders via triturating them w/ a mortar & pestle or w/ spatula on ointment slab, along w/ a small amount of liquid in which the powdered substance is insoluble in

What is the levigating agent?

Agent used for levigation & is typically viscous & w/ low surface tension to wet solid particles. Act as lubricants allowing easier incorporation of insoluble solids into liquids when preparing suspensions

What is geometric dilution?

Mixing a small amount of solid (powder) of an API w/ a large amount of excipient or diluent (powder too)

What are the steps of geometric dilution?

1. Small quantity of API powder is placed in mortar w/ equal amount of other powder (excipient/diluent)

2. 2 materials are triturated until they are well mixed

3. Equal amount of diluent added again to mixture

4. Trituration repeated until they are mixed

5. Steps 2-4 repeated until all powders are combined & mixed