Pharmaceutical Suspensions Quiz
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Questions and Answers

What is the primary role of wetting agents in a suspension?

  • To enhance the flavor of the liquid medium
  • To increase the particle size of the solid
  • To stabilize the suspension against gravitational sedimentation
  • To reduce interfacial tension between solid particles and liquid medium (correct)

Which of the following wetting agents is specifically noted for parenteral use?

  • Glycerol
  • Sodium lauryl sulfate
  • Pluronics (correct)
  • Acacia

What is a disadvantage of using surfactants as wetting agents?

  • They can increase the solubility of drugs.
  • They facilitate faster drug absorption.
  • They decrease interfacial tension.
  • They may cause excessive foaming. (correct)

What effect do trivalent ions have when added to a flocculated suspension?

<p>They assist in forming a flocculated system. (C)</p> Signup and view all the answers

Which hydrophilic polymer is NOT listed among those used as wetting agents?

<p>Collagen (C)</p> Signup and view all the answers

How do solvents like glycerol contribute to wetting in a suspension?

<p>By reducing liquid/air interfacial tension (D)</p> Signup and view all the answers

When might the use of excessive electrolyte in a suspension lead to problems?

<p>It may cause charge reversal on the particles. (C)</p> Signup and view all the answers

What is the function of hydrophilic polymers when added to a solid in a liquid medium?

<p>To impart a hydrophilic character to the solid (D)</p> Signup and view all the answers

What is the maximum concentration of Carbapol that can be used mainly for external applications?

<p>0.5% (C)</p> Signup and view all the answers

How do hydrated silicates like Bentonite need to be processed prior to use in external preparations?

<p>They should be sterilized. (A)</p> Signup and view all the answers

Which of the following cellulose derivatives is used as a suspending agent?

<p>Microcrystalline cellulose (A), Carboxymethyl cellulose (D)</p> Signup and view all the answers

What is the potential issue arising from high concentrations of sweetening agents in a suspension?

<p>Newtonian properties affecting rheological characteristics (D)</p> Signup and view all the answers

Which suspending agent can be used in both internal and external applications?

<p>Veegum (A)</p> Signup and view all the answers

What role do buffers play in suspension formulations?

<p>Maintain chemical stability and tonicity (D)</p> Signup and view all the answers

Which of the following substances can be used as humectants in suspension formulations?

<p>Propylene glycol (A)</p> Signup and view all the answers

What is the purpose of preservatives in suspension formulations?

<p>Prevent the growth of microorganisms (B)</p> Signup and view all the answers

What is the effect of non-ionic surfactants on particle charge density?

<p>They have little effect on the charge density. (D)</p> Signup and view all the answers

What happens to the positive zeta potential when monobasic potassium phosphate is added to bismuth subnitrate particles?

<p>It decreases due to adsorption of negatively charged phosphate anions. (C)</p> Signup and view all the answers

Which statement correctly explains the correlation between zeta potential and sedimentation volume?

<p>Sedimentation volume increases with a decrease in zeta potential. (D)</p> Signup and view all the answers

What type of agent is dibasic potassium phosphate when used with bismuth subnitrate suspension?

<p>Flocculating agent. (C)</p> Signup and view all the answers

Which of the following polymeric flocculating agents creates a gel-like network in the dispersed phase?

<p>Alginates, cellulose derivatives, and starch. (D)</p> Signup and view all the answers

What occurs to the sedimentation volume when the zeta potential becomes sufficiently negative?

<p>It starts to decrease, indicating higher flocculation. (D)</p> Signup and view all the answers

Why does acacia gum become acidic upon storage?

<p>Due to enzyme activity causing oxidation. (A)</p> Signup and view all the answers

What is a disadvantage of sodium alginate when used in dispersions?

<p>It has an anionic character that causes incompatibility with cationic materials. (A)</p> Signup and view all the answers

What happens when the sedimentation volume 'F' is equal to 1?

<p>The final sediment volume is equal to the original suspension volume. (B)</p> Signup and view all the answers

How is the degree of flocculation 'β' calculated?

<p>β = F / Fα (C)</p> Signup and view all the answers

What is the likely result of using large particles in ophthalmic suspension?

<p>A gritty texture that may irritate the eyes. (C)</p> Signup and view all the answers

What does a sedimentation volume 'F' greater than 1 indicate?

<p>The sediment is flocculated with a loose structure. (B)</p> Signup and view all the answers

Which is NOT a method of preparing suspensions?

<p>Increasing the drug's temperature continuously (D)</p> Signup and view all the answers

What parameter is considered more fundamental than sedimentation volume in suspension analysis?

<p>Degree of Flocculation 'β' (B)</p> Signup and view all the answers

What term describes the final sediment volume of deflocculated suspension?

<p>Fα (C)</p> Signup and view all the answers

What is the outcome of particle size growth during storage of a drug?

<p>Crystallization and increased particle size (C)</p> Signup and view all the answers

Flashcards

Sedimentation Volume (F)

The ratio of the final sediment volume (Vf) to the original volume of the suspension (Vo). It indicates the degree of flocculation.

Degree of Flocculation (β)

A parameter that compares the sedimentation volume of a flocculated suspension (F) to the sedimentation volume of a completely deflocculated suspension (Fα).

F = 1 (Flocculated)

A suspension with a sedimentation volume (F) equal to 1. This means the final sediment volume is the same as the original suspension volume. It indicates good flocculation with no clear supernatant.

F < 1 (Deflocculated)

A suspension with a sedimentation volume (F) less than 1. The final sediment volume is smaller than the original suspension volume.

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F > 1 (Loose Flocculation)

A suspension with a sedimentation volume (F) greater than 1. The final sediment volume is larger than the original suspension volume. This happens when flocks are loose and fluffy.

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Particle Size Control (Suspensions)

The process of reducing the particle size of a solid drug in a suspension. This is important to prevent grittiness, irritation, and needle blockage.

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Wetting Agents (Suspensions)

Substances added to a suspension to improve the wettability of the solid drug particles. This helps to prevent clumping and improve dispersibility.

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Flocculating Agents (Suspensions)

Substances added to a suspension to encourage the formation of flocs. This helps stabilize the suspension and prevent settling.

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Particle Size and Solubility

Smaller crystals (less than 1 μm) dissolve faster than larger crystals. This is because smaller crystals have a greater surface area in contact with the solvent.

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What do wetting agents do?

Wetting agents reduce the surface tension between solid particles and the liquid, allowing the liquid to spread easier and wet the particles.

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Surfactants as wetting agents

Surfactants are a type of wetting agent with a specific HLB value (hydrophile-lipophile balance) that are commonly used in oral, external, and parenteral formulations.

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Hydrophilic polymers as wetting agents

Hydrophilic polymers like acacia, bentonite, and tragacanth coat hydrophobic particles, making them easier to wet.

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Solvents as wetting agents

Alcohols like ethanol and glycerol reduce surface tension and help liquids wet particles effectively.

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Flocculation: What does it mean?

Flocculating agents cause particles in a suspension to clump together, forming a loose network.

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Electrolytes as flocculating agents

Electrolytes like sodium salts can reduce the zeta potential of particles, causing them to flocculate.

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Surfactants as flocculating agents

Ionic surfactants can also cause flocculation by neutralizing the charge on particles.

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Flocculation

The process of forming loose, fluffy clusters of particles in a suspension, often induced by the addition of flocculating agents.

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Sedimentation Volume

The ability of a suspension to resist settling. A higher sedimentation volume means the suspension is more stable.

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Zeta Potential

The measurement of the electrical charge on the surface of a particle in a suspension. It plays a crucial role in determining the stability of the suspension.

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Flocculating Agent

A substance that reduces the zeta potential of particles in a suspension, promoting flocculation or aggregation.

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Viscosity Modifier

A substance that increases the viscosity of the suspension, helping to hold the particles in suspension for longer.

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Wetting Agent

A substance that increases the wettability of solid drug particles, ensuring they disperse evenly in the suspension.

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Caking Preventative

A substance added to a suspension to prevent caking, a process where particles settle and form a solid mass.

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Deflocculating Agent

A substance added to a suspension to prevent flocculation, keeping particles dispersed.

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Suspending Agents

Suspending agents are used to keep solid particles dispersed in a liquid, preventing them from settling. They increase the viscosity of the suspension.

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Cellulose Derivatives

Cellulose derivatives, like methylcellulose and hydroxypropyl cellulose, are commonly used suspending agents. They form a viscous solution that holds the solid particles in suspension.

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Hydrated Silicates

Hydrated silicates, such as bentonite, magnesium aluminum silicate, and hectorite, readily absorb water, forming a gel-like structure that suspends solid particles.

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Carbapol

Carbapol is a synthetic polymer that forms a gel-like network when dissolved in water, suspending solid particles.

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Colloidal Silicone Dioxide (Aerosil)

Colloidal silicone dioxide, or Aerosil, forms a three-dimensional network when dispersed in water, suspending solid particles.

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Buffers

Buffers help control the pH of a suspension, ensuring stability and compatibility with the body.

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Density Modifiers

Density modifiers, like sucrose or glycerol, are added to make the density of the solid particles and the liquid phase similar, preventing sedimentation.

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Preservatives

Preservatives are added to prevent the growth of microorganisms in a suspension, ensuring its safety and extending its shelf life.

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Study Notes

Pharmaceutical Suspension

  • Suspensions are pharmaceutical preparations where solid particles are dispersed in a liquid medium
  • Sedimentation parameters are used to assess suspension stability.
    • Sedimentation volume (F): The ratio of final sediment volume (Vf) to the original suspension volume (Vo). A value of F < 1 indicates the final sediment volume is less than the original suspension volume. F = 1 indicates the final sediment volume equals the original suspension volume. If F > 1, the final sediment volume exceeds the original suspension volume.
    • Degree of flocculation (β): A more fundamental parameter relating the volume of flocculated sediment to a deflocculated system. It is calculated as β = Ff/Fα = Vf/Vα, where Fα and Vα represent the sedimentation volume and final sediment volume of a deflocculated system, respectively.

Preparation of Suspensions

  • Particle Size Control:

    • Large particles (greater than 5 µm) in ophthalmic suspensions cause irritation.
    • Large particles in parenteral suspensions can block needles.
    • Changes in temperature can cause drug crystallization, increasing particle size during storage. Drug solubility can be affected, and smaller particles may have higher solubility than larger ones.

  • Use of Wetting Agents:

    • Wetting agents reduce interfacial tension between solid particles and liquid medium.
    • This allows displacement of air from the solid surfaces.
    • Adequate wetting of the particles throughout the liquid is achieved.

  • Types of Wetting Agents:

    • Surfactants (HLB value 7-9) at concentrations of up to 0.1%
      • Tweens and Spans (oral use)
      • Sodium lauryl sulfate, Sodium dioctylsulphosuccinate (external use)
      • Tweens, Pluronics, Lecithin (parenteral use)
    • Disadvantages of surfactant use: excessive foaming, and the creation of a deflocculated system.

  • Hydrophilic Polymers and Hydrocolloids:

    • Materials that coat hydrophobic particles with a multimolecular layer, changing the solid from hydrophobic to hydrophilic
    • Examples: acacia, bentonite, tragacanth, alginates, cellulose derivatives.

  • Solvents:

    • Alcohol, glycerol, and glycols reduce liquid/air interfacial tension, aiding wetting in the dispersion medium

Use of flocculating agents

  • Electrolytes:
    • Sodium salts of acetates, phosphates, and citrates are common electrolytes
    • Addition of electrolytes reduces zeta potential of dispersed particles, promoting flocculation
    • Flocculating ability of electrolytes depends on the valence of their counter-ions. Trivalent ions are more effective but less used due to toxicity. If hydrophilic polymers are present, these polymers may be precipitated if using trivalent ions
  • Surfactants:
    • Ionic surfactants help by neutralizing the charge on each particle
    • Non-ionic surfactants may affect the charge density of a particle but form a loose structure through linear configuration adsorption.

Viscosity Modifiers (Suspending Agents)

  • Polysaccharides:
    • Acacia gum: acidification and potential oxidation-related problems
    • Tragacanth: better thickening agent than acacia
    • Alginates: Sodium alginate is the most used, but its anionic character makes it incompatible with heavy metals. Large increase in viscosity when calcium chloride is added
    • Starch: Sodium starch glycollate, a starch derivative, is used.
  • Water-soluble cellulose: Derivatives like Methyl cellulose, Hydroxyethyl cellulose, Carboxymethyl cellulose and Microcrystalline cellulose
  • Hydrated silicates: Bentonite, Magnesium aluminum silicate (Veegum), Hectorite, and Carbopol

Other Formulation Additives in Suspensions

  • Buffers: Maintain chemical stability and control tonicity
  • Density Modifiers: Glycerol, propylene glycol, and sucrose keep suspension particles at a consistent density to prevent sedimentation.
  • Flavours, colours, and perfumes: Improve organoleptic properties of the suspension
  • Humectants: Prevent drying to skin after application
  • Preservatives: prevent microbial growth, e.g. heating dry powder, autoclaving
  • Sweeteners: Sorbitol, glycerol, or sucrose can negatively impact the suspension's properties and need to be accounted for

Stability Testing of Suspension

  • Physical stability: Analyzed through sedimentation rate, initial/final volume, flocculation value, and redispersion ease.
  • Chemical stability: Assessed by concentration of active ingredients over time.

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Pharmaceutical Suspension Lecture Notes PDF

Description

Test your knowledge on pharmaceutical suspensions, including their preparation and stability parameters. This quiz covers key concepts such as sedimentation volume and degree of flocculation. Challenge yourself to understand the intricacies of suspension formulations.

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