Creams

Flashcards about pharmaceutical creams

What are Creams?

Topical applications that are semisolid emulsions.

Give examples of liquid and solid topical applications.

Dusting powders, solutions, suspensions, lotions, shampoos, and washes.

Give examples of semisolid topical applications.

Creams, ointments, pastes, and gels.

What is a key characteristic of semisolids?

They cling to the surface of the skin until washed or worn off.

Describe ointments.

Translucent, greasy, with oil as the main component.

Describe pastes.

Opaque ointments with a high concentration of insoluble particulate solid.

Describe gels.

Transparent semisolid systems with a high percentage of water trapped within a polymer matrix.

Describe creams

Semisolid emulsions of two immiscible phases stabilized by an emulsifying agent.

What are the two main types of creams?

Oil-in-water (o/w) and water-in-oil (w/o).

What are the phases in o/w creams?

Water is the continuous medium, and oil is the dispersed phase.

What are the characteristics of o/w creams?

Do not feel greasy, leave a thin film, readily diluted and miscible with water, conduct electricity.

What type of surfactants are used to prepare o/w creams?

Surfactants with higher HLB (8-16).

What is the continuous phase in w/o creams?

Oil is the continuous phase.

What are the characteristics of w/o creams?

More greasy, hydrophobic drugs are readily released, more moisturizing, not easily washable, do not conduct electricity.

What type of surfactants are used to prepare w/o creams?

Low HLB surfactants (3.5-8).

What determines the type of cream prepared (o/w or w/o)?

The type of surfactant used.

What happens with excess surfactant in creams?

Excess surfactant forms structures in the bulk phase, producing complex semi-solid multiphase systems.

What are the at least 4 phases observed in o/w creams?

Dispersed oil phase, crystalline gel phase, crystalline hydrated phase, and bulk water phase.

What is the overall stability of the cream dependent on?

The stability of the crystalline gel phase.

What is the purpose of the multilayers in the crystalline gel phase?

Protects against coalescence of droplets by retarding their movement.

What is the general method for preparing creams?

Heating the oily phase and aqueous phase separately and then mixing them with constant stirring.

What can result in separation during cream preparation?

Rapid cooling and insufficient mixing.

What are the two methods of drug incorporation?

Fusion and trituration.

Describe the fusion method of drug incorporation.

Drug and cream ingredients are melted together and stirred to ensure homogeneity.

When should heat not be used in the fusion method?

Heat labile/sensitive drugs.

How are heat labile or insoluble solids or liquids incorporated into bases?

Mixing by trituration.

What is used to work the material together during trituration?

A flexible spatula.

Generally, how effective are emollients?

The greasier, the more effective it is at trapping moisture.

Compare creams to ointments.

Creams are less greasy but generally more acceptable than ointments.

When are lotions good to recommend?

Very mild dry skin and for the face, especially in hairy areas.

When should ointments not be used?

Where an infection is present.

What can overuse of greasy ointments lead to?

Folliculitis.

What is the consistency of creams?

Semi-solid emulsions.

What determines whether you get an o/w or w/o cream?

The choice of surfactant mixture.

What concentration of emulsifiers is needed for stability and viscosity?

Higher concentrations of emulsifiers.

What governs the stability of the cream?

The repulsions between the droplets and the gel crystalline phase.

What factors can greatly affect the stability and consistency of the cream produced?

The preparation method e.g. heating/cooling or speed of homogenisation.

Define topical semisolids.

Semisolids that cling to the skin's surface until washed off.

How do w/o creams moisturize the skin?

They provide an oily barrier, reducing water loss and hydrating the skin.

What temperature-related step is crucial in cream preparation?

Heating the components to the same temperature before mixing.

Describe the process of diluting the dispersion with increasing amounts of base in trituration.

Mixing small quantities of the base at a time and doubling the quantity with each addition.

What type of drugs should not be heated during fusion?

Heat labile drugs should not be heated during fusion.