Suspensions in Pharmaceutics

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Questions and Answers

What is a primary advantage of using aqueous suspensions for drug administration?

They enhance the flavor of poorly soluble drugs.

They provide a high availability for dissolution and absorption. (correct)

They allow drugs to be administered in solid form.

They eliminate the need for chemical stability.

Which feature is NOT desirable in a pharmaceutical suspension?

Chemical stability of components.

Esthetic appeal of the preparation.

Therapeutic efficacy.

Rapid settling of suspended particles. (correct)

Why are certain drugs formulated as oral suspensions rather than solutions?

To improve their solubility in water.

To simplify dosing measurements.

To reduce the production costs.

To overcome unpleasant taste in solution form. (correct)

What is an ideal characteristic of the particle size in a pharmaceutical suspension?

Particle size must remain fairly constant over time. Signup and view all the answers

What happens to particles in an acceptable suspension that settle to the bottom of the container?

They must be easily re-dispersed upon shaking. Signup and view all the answers

What describes the physical stability of an ideal pharmaceutical suspension?

Particles do not aggregate and remain uniformly distributed. Signup and view all the answers

Which feature is important regarding the viscosity of a pharmaceutical suspension?

The suspension should pour freely and not be too viscous. Signup and view all the answers

What is a purpose of developing less water-soluble forms of certain drugs?

To enhance palatability in liquid formulations. Signup and view all the answers

Which milling method is particularly effective for producing particles under 10 μm?

Fluid energy grinding Signup and view all the answers

What is a disadvantage of using extremely fine particles in suspensions?

They can form a compact cake upon settling. Signup and view all the answers

What effect does reducing the particle size have on the sedimentation rate of solid particles in a suspension?

It decreases sedimentation rate. Signup and view all the answers

Which particle shape is associated with more stable suspensions?

Symmetrical barrel-shaped particles Signup and view all the answers

What is a common method for preventing rigid cohesion of small particles in a suspension?

Intentionally forming loose aggregations Signup and view all the answers

Which of the following describes a disadvantage of the mortar and pestle compared to other comminuting equipment?

It achieves a higher degree of particle size reduction. Signup and view all the answers

Which process rapidly dries a drug solution to form a powder?

Spray drying Signup and view all the answers

What could result from excessive reduction of particle size in a suspensoid?

Formation of a caking sediment Signup and view all the answers

What does Stoke's law primarily describe?

The rate of settling of particles in a suspension Signup and view all the answers

According to Stoke's law, which factor does NOT directly affect the sedimentation rate?

Particle shape and uniformity Signup and view all the answers

How does particle size affect the rate of descent in a suspension?

Larger particles fall faster than smaller ones Signup and view all the answers

What is one consequence of increasing the viscosity of the dispersion medium?

Reduces the sedimentation rate Signup and view all the answers

What is a common method for reducing particle size in pharmaceuticals?

Micropulverization Signup and view all the answers

What is the effect of having a higher particle density than the vehicle in a suspension?

Promotes faster sedimentation rates Signup and view all the answers

What is a characteristic of the ideal scenario described by Stoke's law?

Uniform, perfectly spherical particles Signup and view all the answers

Which of the following best describes the trade-off when increasing viscosity in a suspension?

It makes it easier to disperse but harder to pour Signup and view all the answers

What is the primary characteristic of flocculated particles compared to unflocculated particles?

They settle more rapidly and form loosely packed sediments. Signup and view all the answers

What happens to the sediment volume when flocculated particles settle?

It forms a higher sediment volume than unflocculated particles. Signup and view all the answers

What effect does the rapid settling of large particles have on dosage measurement?

It hinders accurate measurement of dosage. Signup and view all the answers

What distinguishes the appearance of a suspension of flocculated particles from one containing unflocculated particles?

Flocculated suspensions have a pleasing appearance. Signup and view all the answers

How do flocculated particles behave during agitation compared to unflocculated particles?

Flocculated particles break up easily while unflocculated do not. Signup and view all the answers

What is a key challenge associated with sediment formed from deflocculated particles?

It packs into a dense sediment. Signup and view all the answers

What type of sediment do flocculated particles form?

Light and loosely packed. Signup and view all the answers

Which of the following is a common method for preparing flocculated suspensions?

Aggregation of particles. Signup and view all the answers

What role do flocculating agents like bentonite magma play in oral suspensions?

They help support the formation of the floc. Signup and view all the answers

What is the purpose of altering the pH in a parenteral suspension?

To produce a floc of the dispersed phase. Signup and view all the answers

How do electrolytes function as flocculating agents?

By bridging and linking particles together. Signup and view all the answers

What is a disadvantage of using certain polymeric substances as suspending agents?

They can bind medicinal agents, making them unavailable. Signup and view all the answers

Which of the following best describes the primary difference between suspensions and colloidal dispersions?

Suspensions have larger dispersed particles than colloids. Signup and view all the answers

What is a key consideration when determining the concentration of suspending agents?

It must not impede the drug's availability. Signup and view all the answers

What effect do surfactants have on particles in a suspension?

They induce flocculation and increase sedimentation. Signup and view all the answers

What issue arises if the concentration of the suspending agent is too high?

The suspension may become too viscous to pour. Signup and view all the answers

Study Notes

Suspensions

Suspensions are liquid dosage forms where insoluble or poorly soluble drugs are dispersed in a liquid.
They offer advantages like:
- High bioavailability due to large surface area of dispersed drug, ensuring rapid dissolution and absorption.
- Chemical stability for drugs that are unstable in solution but stable in suspension.
- Improved palatability compared to solutions, especially for poorly tasting drugs.
Desired features of suspensions:
- Therapeutic efficacy.
- Chemical stability of components.
- Permanency of the preparation.
- Aesthetic appeal.
Specifications of suspensions:
- Slow settling rate with easy redispersion when shaken.
- Stable particle size over time.
- Pour-ability and flow through syringes.
Ideal suspensions exhibit physical stability, meaning particles remain uniformly distributed.
Settling rate of particles is governed by Stoke's Law, which considers factors like:
- Particle diameter (d)
- Particle density (ρi)
- Medium density (ρe)
- Gravitational constant (g)
- Medium viscosity (η)
Factors affecting sedimentation rate:
- Smaller particle size leads to slower settling rate.
- Higher particle density results in faster settling.
- Increased viscosity of the medium slows down sedimentation.
Particle size reduction techniques:
- Micropulverization: Produces particles 10-50 μm, suitable for most oral and topical suspensions.
- Fluid energy grinding (jet milling): Produces particles under 10 μm, suitable for parenteral and ophthalmic suspensions.
- Spray drying: Creates extremely small particles, used for specialized applications.
Advantages of particle size reduction includes:
- Reduced sedimentation rate for better stability.
- Slow, uniform settling.
However, excessive particle size reduction can create a compact cake, which is difficult to redisperse.
Shape of particles also influences caking:
- Symmetrical particles like barrel-shaped calcium carbonate form stable suspensions.
- Asymmetrical particles like needle-shaped calcium carbonate tend to form tenacious sediment cakes.
Flocculation prevents caking:
- Flocculating agents like bentonite magma create loose aggregates (flocs) that resist compaction.
- Flocs settle faster but are easily redispersed.
Comparison of deflocculated and flocculated suspensions:
- Deflocculated: Particles settle slowly, forming a compact cake.
- Flocculated: Particles settle rapidly, forming a loose sediment that is easily redispersed.
Methods of flocculation:
- Clays like bentonite magma act as flocculating agents in oral suspensions.
- pH adjustment can induce flocculation in parenteral suspensions.
- Electrolytes can bridge particles and promote flocculation.
- Carefully chosen surfactants can also induce flocculation.
Suspending agents are used to thicken the dispersion medium and prevent settling.
Examples of suspending agents include:
- Carboxymethylcellulose (CMC)
- Methylcellulose
- Microcrystalline cellulose
- Xanthan gum
- Polyvinylpyrrolidone
- Bentonite
Important considerations for suspending agents are:
- Avoiding interference with drug availability.
- Avoiding viscosity that hinders agitation and pouring.
Key difference between suspensions and colloids:
- Size of dispersed particles: Suspensions have larger particles prone to sedimentation.
Suspensions share many other properties of colloidal systems.

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Description

Explore the characteristics and advantages of suspensions as liquid dosage forms in this quiz. Understand their importance in providing high bioavailability and chemical stability for drugs. Test your knowledge of the desired features and specifications that make suspensions effective and appealing.