10 Questions
What is the purpose of reducing the particle size of a powder or crystalline material before incorporating it into an ointment base?
To prevent the final product from being gritty.
What is the process of mixing a solid material in a vehicle in which it is insoluble to make a smooth dispersion called?
Levigation.
What is the recommended volume ratio between the levigating agent and the solid material?
The levigating agent should be about equal in volume to the solid material.
What is the preferred tool for levigation?
Mortar and pestle.
How can solids soluble in a common solvent be incorporated into ointments?
By first dissolving them in the solvent and then adding the solution.
When preparing an ointment by spatulation and the components react with metal, what type of spatulas can be used?
Hard rubber or silicone spatulas.
What should the levigating agent be compatible with, both physically and chemically?
The drug and the ointment base.
What is the purpose of incorporating solids into ointment bases?
To improve the texture and consistency of the ointment.
Why is it important to use appropriate spatulas when preparing ointments?
To avoid reactions between the components and metal.
What method is preferred when large volumes of liquid need to be added during ointment preparation?
Mortar and pestle method.
Study Notes
Semisolid Dosage Forms: Ointments, Creams, and Gels
- Semisolid dosage forms are intended for topical application to the skin, eyes, or other mucous membranes.
- They can be medicated or unmedicated, with unmedicated ones used for physical effects as protectants or lubricants.
- Topical applications can be designed for local effects or systemic absorption.
Ointments
- Ointments are semisolid preparations intended for external application to the skin or mucous membranes.
- They can be medicated or unmedicated, with unmedicated ones used for physical effects as protectants, emollients, or lubricants.
- Medicated ointments consist of a drug and an ointment base.
- Ointment bases can be classified into four types: oleaginous, absorption, water-removable, and water-soluble bases.
Ointment Bases
- Oleaginous Bases: provide occlusion, used as protectants, emollients, or lubricants.
- Absorption Bases: permit the incorporation of aqueous solutions, may be used as emollients, not easily removed by water washing.
- Water-Removable Bases: not mentioned in the text.
- Water-Soluble Bases: do not contain oleaginous components, completely water washable, often referred to as greaseless.
Examples of Ointment Bases
- White Vaseline: an oleaginous base, prepared by mixing yellow wax and petrolatum.
- Hydrophilic Ointment: an absorption base, prepared by mixing stearyl alcohol, white petrolatum, and purified water.
- Polyethylene Glycol (PEG) Ointment: a water-soluble base, prepared by mixing PEG 3350 and PEG 400.
Selection of the Appropriate Base
- Depends on the desired release rate of the drug substance.
- Depends on the desirability of topical or percutaneous drug absorption.
- Depends on the desirability of occlusion of moisture from the skin.
- Depends on the stability of the drug in the ointment base.
- Depends on the effect of the drug on the consistency or other features of the ointment base.
- Depends on the desire for a base easily removed by washing with water.
- Depends on the characteristics of the surface to which it is applied.
Preparation of Ointments
- Incorporation: mixing until a uniform preparation is attained, using a mortar and pestle, ointment mill, or other devices.
- Fusion: not mentioned in the text.
- Incorporation of Solids: may require reducing particle size of powder or crystalline material, using levigation and spatulation.
- Levigation: mixing the solid material in a vehicle in which it is insoluble, to make a smooth dispersion.
Explore the characteristics and applications of semisolid dosage forms like ointments, creams, and gels used for topical application. Learn about the differences between medicated and unmedicated preparations and their intended effects.
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