Pharmaceutical Suspensions Overview

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Questions and Answers

What is the primary function of flocculating agents in suspensions?

Promote particle aggregation. (correct)

Increase the sedimentation volume.

Enhance the wetting of dispersed phases.

Decrease the viscosity of the medium.

Which type of suspension is characterized by fast settling and easily redispersed floccules?

Flocculated suspension (correct)

Deflocculated suspension

Coalesced suspension

Stable suspension

How does temperature affect the solubility of drugs during crystal growth?

Increases with a decrease in temperature.

Increases with an increase in temperature. (correct)

Decreases with an increase in temperature.

Remains constant regardless of temperature.

What is the role of suspending agents in a suspension?

Increase the viscosity of the medium to slow sedimentation. Signup and view all the answers

What does a higher sedimentation volume indicate about a suspension?

Better suspendibility. Signup and view all the answers

Which of the following is NOT a type of flocculating agent?

Suspending agents Signup and view all the answers

What is the purpose of wetting agents in a suspension?

Help the dispersed phase become more penetrable by water. Signup and view all the answers

What occurs during freeze-thaw cycling in suspension evaluation?

Particle size changes are assessed. Signup and view all the answers

What is a characteristic of an ideal suspension regarding sedimentation?

Sediment should be stable for an extended period. Signup and view all the answers

Which of the following factors increases the sedimentation rate according to Stokes' law?

Increased density of the dispersed phase Signup and view all the answers

Which method is primarily used for particle size reduction in most suspensions?

Dry milling Signup and view all the answers

What is the ideal particle size range for preparing suspensions?

1 - 50 µm Signup and view all the answers

In which scenario might a suspension be preferable to a solution?

Improved palatability of a drug with an undesirable taste Signup and view all the answers

What is the effect of increasing the viscosity of the medium in a suspension?

Slower settling of particles Signup and view all the answers

Which of the following is NOT a desirable feature of a suspension?

High sedimentation rate Signup and view all the answers

What is the sedimentation rate of 2.5 µm powder in water?

1.02 x 10⁻⁴ cm/s Signup and view all the answers

Study Notes

Suspensions

Suspensions are preparations with finely divided drug particles distributed throughout a liquid, typically water, where the drug has minimal solubility.
Some suspensions are ready-to-use, while others are dry powders that need reconstitution.
Suspensions can be for oral, topical, or parenteral administration.

Reasons for Suspension Preparation

Certain drugs are unstable in solution but stable in suspension form, maintaining chemical stability while being administered as a liquid.
Liquid dosage forms (suspensions) are often preferred over solid dosage forms due to easier swallowing.
Suspensions can mask unpleasant tastes of some drugs, using insoluble drug particles instead of a solution.

Desirable Features of Suspensions

Properly prepared suspensions should remain homogeneous for the period between shaking and use.
The sediment created during storage should redisperse easily after gentle shaking.
Particle size of the suspended drug should remain constant over time, avoiding crystal growth (physical stability).
Suspension viscosity shouldn't be too high for easy pouring from the container.

Sedimentation Rate

Stokes' law equation describes the factors affecting the rate at which particles settle in a suspension.
Factors influencing sedimentation rate include particle size (larger particles settle faster).
The density of the particles and medium also impact sedimentation rates, with a higher density difference leading to faster sedimentation.
Higher viscosity of the medium slows down sedimentation rate.
Particle size reduction (e.g., dry milling) and controlled viscosity are important factors in suspension stability.

Particle Size Reduction Techniques

Micropulverization is used to produce fine drug powders (10-50 µm) for suspensions.
Jet milling (micronization) creates even finer particles (under 10 µm).
Spray drying is another technique for producing extremely small particles.

Flocculated and Deflocculated Suspensions

In deflocculated suspensions, particles remain separate, settling slowly and often appearing cloudy.
Flocculated suspensions involve aggregation of particles into loose clusters (floccules), leading to faster sedimentation.
Floccules have a more porous, loose structure, allowing easier redispersion after shaking.
Flocculation is preferred over deflocculation for improved stability and ease of redispersion in suspensions.

Evaluation of Suspension Stability

Sedimentation volume is the ratio of the ultimate sediment height to the initial suspension height, reflecting suspendibility.
Higher sedimentation volume ratios are preferred for better suspendibility.
Freeze-thaw cycling is a stability testing technique for evaluating particle growth and potential issues with prolonged storage conditions.

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Description

This quiz covers the fundamentals of pharmaceutical suspensions, including their preparation, reasons for use, and desirable features. It highlights the importance of maintaining stability and homogeneity in suspensions for effective drug administration. Test your knowledge on the characteristics and applications of suspensions in medicine.