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Questions and Answers
What is a potential effect of aluminum hydroxide on drug absorption?
What is a potential effect of aluminum hydroxide on drug absorption?
What change may be necessary when aluminum hydroxide gel is administered with other drugs?
What change may be necessary when aluminum hydroxide gel is administered with other drugs?
Which statement accurately describes Milk of Magnesia?
Which statement accurately describes Milk of Magnesia?
What should pharmacists ensure when dispensing reconstituted products?
What should pharmacists ensure when dispensing reconstituted products?
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What is a characteristic of starch glycerite?
What is a characteristic of starch glycerite?
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What is the size range of particles in colloidal dispersions?
What is the size range of particles in colloidal dispersions?
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Which type of colloidal particle would likely have more interaction with the dispersing medium?
Which type of colloidal particle would likely have more interaction with the dispersing medium?
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What characterizes lyophobic colloids compared to lyophilic colloids?
What characterizes lyophobic colloids compared to lyophilic colloids?
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What phenomenon describes gels that become fluid upon agitation and revert to a solid state after settling?
What phenomenon describes gels that become fluid upon agitation and revert to a solid state after settling?
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Which statement about amphiphilic colloids is true?
Which statement about amphiphilic colloids is true?
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How do lyophilic colloids react to an increase in concentration of the disperse phase?
How do lyophilic colloids react to an increase in concentration of the disperse phase?
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What type of sol is characterized by a dispersion of a solid in a liquid medium?
What type of sol is characterized by a dispersion of a solid in a liquid medium?
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Which of the following describes inorganic gels?
Which of the following describes inorganic gels?
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Which type of gel includes hydrocarbon-based substances, animal fats, and vegetable fats?
Which type of gel includes hydrocarbon-based substances, animal fats, and vegetable fats?
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What is the primary characteristic of the majority of organic gels?
What is the primary characteristic of the majority of organic gels?
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What is the effect of shaking magmas and gels before use?
What is the effect of shaking magmas and gels before use?
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Which gelling agent can swell in water to about 200 to 300 times its own weight without dissolving?
Which gelling agent can swell in water to about 200 to 300 times its own weight without dissolving?
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How do colloidal silicon dioxide and methylcellulose primarily function in gels?
How do colloidal silicon dioxide and methylcellulose primarily function in gels?
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What happens as a hot colloidal dispersion of gelatin cools?
What happens as a hot colloidal dispersion of gelatin cools?
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What stabilizing properties do gelling agents possess?
What stabilizing properties do gelling agents possess?
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Which thickening agent is noted for being used in the preparation of gels?
Which thickening agent is noted for being used in the preparation of gels?
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What property of polymer solutions contributes to the formation of gels?
What property of polymer solutions contributes to the formation of gels?
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How do inorganic salts affect gelation in aqueous solutions?
How do inorganic salts affect gelation in aqueous solutions?
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What is the recommended storage time for aqueous polymer solutions to enhance their properties?
What is the recommended storage time for aqueous polymer solutions to enhance their properties?
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Which of the following is NOT a characteristic of Bentonite Magma, NF?
Which of the following is NOT a characteristic of Bentonite Magma, NF?
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What is a noted disadvantage of Aluminum Hydroxide Gel, USP?
What is a noted disadvantage of Aluminum Hydroxide Gel, USP?
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Which ingredient is typically added to Aluminum Hydroxide Gel, USP for flavoring?
Which ingredient is typically added to Aluminum Hydroxide Gel, USP for flavoring?
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What action does Aluminum Hydroxide Gel, USP perform in the stomach?
What action does Aluminum Hydroxide Gel, USP perform in the stomach?
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What is the main purpose of Sodium Fluoride and Phosphoric Acid Gel, USP?
What is the main purpose of Sodium Fluoride and Phosphoric Acid Gel, USP?
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Study Notes
Introduction to Colloidal Dispersions
- Colloidal dispersions are mixtures of particles between 1 nm and 0.5 µm in size.
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Sol: a dispersion of a solid in a liquid, solid, or gaseous medium.
- Hydro- for water (hydrosol)
- Alco- for alcohol (alcosol)
- Aerosol: a dispersion of a solid or liquid in a gaseous medium.
Differences Between Colloidal Dispersions and True Solutions
- Colloidal dispersions have larger particle sizes than true solutions.
- The nature of the dispersing media influences the ease of preparation, character of the dispersion, and the interaction between the disperse phase and the dispersing media.
- Lyophilic: The disperse phase interacts strongly with the dispersion medium (solvent loving).
- Lyophobic: The disperse phase has minimal interaction with the dispersion medium (solvent hating).
Types of Colloidal Sols
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Lyophilic colloids:
- Composed of large organic molecules that readily form colloidal dispersions.
- Viscosity increases as more molecules are added, potentially forming gels.
- Gels: Solids or semisolids formed by a network of the disperse phase that entraps the dispersion medium.
- Some gels can transition between liquid and solid states with temperature changes.
- Thixotropy: Fluidity on agitation, followed by solidification when undisturbed.
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Lyophobic colloids:
- Typically inorganic particles with minimal interaction with the dispersing media.
- Require special preparation methods to form dispersions.
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Amphiphilic colloids:
- Form dispersions in both aqueous and nonaqueous media.
Classification and Types of Gels
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Inorganic and Organic Gels:
- Inorganic hydrogels, like aluminum hydroxide gel and bentonite magma, are typically two-phase systems.
- Organic gels, like carbomer and tragacanth, are usually single-phase systems.
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Hydrogels and Organogels:
- Hydrogels: Include organic and inorganic materials, such as gums and silica.
- Organogels: Include fats, greases, and hydrocarbons.
Preparation of Magmas and Gels
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Inorganic Magmas and Gels:
- Often prepared by precipitation or hydration of inorganic chemicals.
- May use thickening agents like propylene glycol and hydroxypropyl cellulose.
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Stability:
- Magmas and gels are generally stable due to the strong attraction between the disperse phase and the aqueous medium.
- They may separate slightly on standing but can be easily re-dispersed by shaking.
Gelling Agents
- Thicken and stabilize liquid solutions by forming an internal structure.
- Act as colloidal mixtures that give the gel a solid-like appearance.
Examples of Gelling Agents
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Alginic acid:
- Swells significantly in water without dissolving.
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Carbomer (Carbopol) resins:
- High-molecular-weight acid-based polymers.
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Colloidal silicon dioxide:
- Absorbs large amounts of water without liquefying.
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Gelatin:
- Dispersed in hot water and cooled to form gels.
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Magnesium aluminum silicate (Veegum):
- Forms a thixotropic gel at 10% concentration.
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Methylcellulose:
- Forms a gel at 5% concentration.
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Other:
- Bentonite, Acacia, Xanthan gum, Tragacanth gum, Povidone, Carboxymethylcellulose, and Sodium th.
Gel Formulation Considerations
- Dissolution: Powdered polymers may form temporary gels with slow dissolution when added to water.
- Kinetic Energy: Gelatin macromolecules lose kinetic energy as a hot colloidal dispersion cools, causing association through dipole-dipole interactions and forming elongated aggregates.
- Polymer Solutions: Entanglement and attraction between polymer chains in solutions can lead to gel formation.
- Inorganic Salts: Inorganic salts can compete with water, causing gelation at lower concentrations. This is usually reversible.
- Storage: Aqueous polymer solutions often require 48 hours of storage after dissolution to ensure full hydration, maximum viscosity, and clarity.
Examples of Magmas and Gels
- Bentonite Magma, NF: Used as a suspending agent.
- Sodium Fluoride and Phosphoric Acid Gel, USP: Topical dental care prophylactic.
- Fluocinonide Gel, USP: Antiinflammatory corticosteroid.
- Tretinoin Gel, USP: Irritant stimulating epidermal cell turnover for acne treatment.
- Other examples: Erythromycin, benzoyl peroxide, and clindamycin topical gels.
Antacids
- Aluminum Phosphate Gel USP: Antacid.
- Aluminum Hydroxide Gel, USP: Antacid, may affect the bioavailability of certain drugs due to chelation and adsorption.
Bentonite Magma, NF
- A 5% bentonite (hydrated aluminum silicate) preparation in purified water.
- Prepared by adding bentonite directly to water in a blender.
- Bentonite swells to 12 times its volume in water.
- Suspending Agent: Suspending capacity is reduced at lower pH values.
Aluminum Hydroxide Gel, USP
- An aqueous gel containing aluminum hydroxide and aluminum oxide (equivalent to 4% aluminum oxide).
- Prepared by chemical reactions.
- White, Viscous Antacid: Neutralizes gastric acid and coats inflamed gastric surfaces.
- Disadvantage: Constipating effects.
- Bioavailability Issues: Interferes with absorption of tetracycline and other drugs by chelation and adsorption.
Milk of Magnesia
- A 7-8.5% magnesium hydroxide preparation.
- Prepared: By reaction between sodium hydroxide and magnesium sulfate.
- Acid-Neutralizing: Usually requires 5 mL dose, higher doses can cause diarrhea.
- Antacid: Often combined with aluminum hydroxide for better buffering and reduced side effects.
Starch Glycerite
- A topical vehicle and protectant containing starch, benzoic acid, purified water, and glycerin.
Proper Administration and Use of Disperse Systems
- Oral Disperse Systems: Administered by spoonful, dropper, or calibrated devices, depending on the dose.
- Reconstituted Products: Require specific instructions for reconstitution, stability, and use.
- Oral Antibiotic Suspensions: May be misadministered into the ear.
- Stability: Many oral dispersions require refrigeration to maintain stability.
- Absorption: Be aware of medications that interfere with absorption of other drugs, such as aluminum hydroxide, cholestyramine, and kaolin.
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Description
Explore the fascinating world of colloidal dispersions, where particle sizes range between 1 nm and 0.5 µm. This quiz will cover the types of colloids, their differences from true solutions, and the impact of the dispersing media. Test your knowledge on lyophilic and lyophobic colloids and their characteristics.
