Pharmaceutical Suspensions Overview

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is primarily measured to assess the physical stability of a suspension?

Total initial volume and height of sediment (correct)

Temperature and pressure conditions

Chemical composition of the ingredients

Particle size distribution

What is the effect of centrifugation on a flocculated system?

It can destroy the structure of the system (correct)

It has no effect on stability

It reduces the rate of sedimentation

It enhances the ease of redispersion

In assessing rheological properties, what should be done to avoid destroying the suspension's structure?

Assess under constant temperature and pressure

Measure at very low shear rates (correct)

Use high shear rates exclusively

Apply mechanical agitation continuously

What do the terms flocculation and deflocculation refer to in suspension stability?

The aggregation and disaggregation of particles Signup and view all the answers

To combine the results from sedimentation techniques and rheological assessments, what is necessary?

Analyze using compatible measurement parameters Signup and view all the answers

Which parameter indicates that sedimentation has ceased?

Constant ratio of sediment to initial volume Signup and view all the answers

What is a suitable mixer for creating a concentrated suspension?

Turbine mixer Signup and view all the answers

What information can centrifugation provide despite its potential to destroy the flocculated structure?

Relative stabilities of various trial preparations Signup and view all the answers

What is the primary reason for finely subdividing drug particles before formulating a suspension?

To decrease the rate of sedimentation of suspended particles Signup and view all the answers

What is a common effect of having particles greater than 25µm in diameter in a parenteral suspension?

Increased risk of needle blockage Signup and view all the answers

Which of the following is true regarding wetting agents in formulations?

Hydrophilic colloids create a multilayer around hydrophobic particles Signup and view all the answers

In the context of suspensions, what is the difference between flocculated and deflocculated systems?

Flocculated systems exhibit a more structured arrangement of particles Signup and view all the answers

What role do viscosity modifiers play in the formulation of suspensions?

They help increase the thickness of the suspension for stability Signup and view all the answers

Which of the following factors can lead to the growth of crystals in a suspension during storage?

Fluctuations in temperature during storage Signup and view all the answers

What is the primary purpose of using wetting agents in suspension formulations?

To reduce the interfacial tension between solid particles and the liquid phase Signup and view all the answers

How does particle shape affect the ease of administration for parenteral suspensions?

Irregularly shaped particles may block the needle Signup and view all the answers

Which thickening agent is suitable for maintaining a stable viscosity at both high and low pH levels?

Methylcellulose Signup and view all the answers

Which factor is crucial for ensuring adequate bioavailability in the manufacture of suspensions?

Particle size reduction to minimize sedimentation Signup and view all the answers

What is the primary function of wetting agents in the preparation of suspensions?

To aid in the dispersion of the powdered drug Signup and view all the answers

How does sodium carboxymethylcellulose behave in the presence of polyvalent cations?

It precipitates and loses viscosity Signup and view all the answers

What is a characteristic property of hydrated silicates used in suspensions?

They can absorb significant amounts of water and form gels Signup and view all the answers

In the context of suspensions, what is the main difference between flocculation and deflocculation?

Flocculation involves particles aggregating, while deflocculation keeps them separate. Signup and view all the answers

Which of the following is NOT typically considered a formulation additive in suspensions?

Sodium chloride Signup and view all the answers

What is the preferred concentration of sodium carboxymethylcellulose recommended for use?

1% Signup and view all the answers

Study Notes

Suspensions

Finely divided insoluble solid particles dispersed in a fluid (dispersion medium)
Particle size classifications dictate different types of solutions (true solution, colloidal solution, suspension)
True solutions have particles < 10⁻⁷ cm
Colloidal solutions have particles between 10⁻⁷ cm and 10⁻⁵ cm
Suspensions have particles > 10⁻⁵ cm

Physical Properties of Well-Formulated Suspensions

Remains homogeneous after shaking and removal of the dose
Resuspension occurs easily with mild shaking
No hard cake formation during shelf life, and easily redisperses
Maintains stability and elegance during shelf life

Parenteral Suspensions

Free from microbial contamination and must maintain sterility
Easily drawn into a syringe and injectable

Pharmaceutical Applications of Suspensions

Used when solid drug swallowing is difficult
Used when drug solubility in an aqueous medium is poor (e.g., hydrocortisone, neomycin)
This approach is particularly beneficial in pharmaceutical formulations where certain active ingredients are prone to hydrolysis or other chemical degradation when exposed to water. By creating an insoluble derivative, these drugs can be effectively delivered in a form that preserves their potency, stability, and therapeutic efficacy, while also facilitating their administration in a convenient suspension form.

Stability

The product exhibits stability for 7 days when stored at room temperature, which typically ranges from 20°C to 25°C (68°F to 77°F). This duration allows for flexibility in handling and transportation before any deterioration occurs.
When refrigerated, with a temperature set between 2°C and 8°C (36°F and 46°F), it maintains stability for up to 14 days, ensuring its efficacy and quality over a longer period, particularly useful for storage and usage in laboratory settings.

Additional Applications of Suspensions

Used for vaccines to build up antibodies
Utilized as X-ray contrast media, enhancing the visibility of internal structures during imaging procedures. (e.g., Barium sulphate)
Used in aerosols

Formulation of Suspensions - Overview

Particle Size Control: Finely dividing the drug decreases sedimentation rate, reduces gritty texture of large particles and potential eye irritation from large particles
Wetting Agents: Wetting agents, also known as surfactants, play a crucial role in various applications by facilitating the interaction between water and insoluble solids. While some solids can be readily wetted and dispersed in water, others may resist wetting due to their hydrophobic properties. The degree of hydrophobicity can significantly vary among different materials. To achieve effective wetting, it is essential to decrease interfacial tension, thus enhancing the spreading and penetration of the liquid over the solid surfaces.
Flocculation/Deflocculation:
- Deflocculated: Particles exist as discrete units, slow sedimentation, sediment compaction. Pleasant appearance, slow settling and A cloudy supernatant indicates the presence of suspended particles. This turbidity often arises when solid particles are not completely settled at the bottom of a container, thus remaining in the liquid phase after centrifugation or sedimentation.
- Flocculated: Particles form loose aggregates, rapid sedimentation, easily redispersable sediment, no hard sediment cake. Unsightly, rapid sedimentation, clear supernatant
Degree of Flocculation: Correct degree is crucial, under-flocculation is undesirable, over-flocculation is irreversible and can lead to inelegant appearance, high viscosity, and difficulties with redispersion.
Rheology of Suspensions: High apparent viscosity at low shear rates for slow settling and good suspension, decreasing viscosity at high shear rates for easy pouring
Viscosity Modifiers:
polysaccharides (Acacia gum, tragacanth, alginates),
water-soluble cellulose (methylcellulose, hydroxypropylcellulose, sodium carboxymethylcellulose),
hydrated silicates (bentonite), colloidal silicone dioxide
Other Formulation Additives: Buffers which maintain chemical stability, density modifiers which ensure sedimentation consistency, flavours, colorants, perfumes, humectants (glycerol, propylene glycol), preservatives, and sweetening agents

Manufacture of Suspensions

Small scale*: This process combines a powdered drug, a suspending agent for uniform dispersion, and a liquid vehicle. A mortar and pestle ensure thorough mixing for consistent formulations and accurate dosing.*
Large scale: Concentrated dispersion of suspending agent is prepared first, then slowly added to the vehicle while mixing. Appropriate mixing equipment like impeller blenders or turbine mixers

Stability Testing of Suspensions

Physical Stability: This concept is critical in understanding the behavior of colloidal systems and dispersions. It can be quantitatively assessed through various parameters including the sedimentation rate, which indicates how quickly particles settle under gravity. Additionally, final volume or height of sediment provides insights into the concentration and stability of the dispersion over time. The ease of redispersion, evaluated through the V/Vo ratio compared over a specified timeline, assesses the ability of the sediment to return to a dispersed state after settling.
Centrifugation: Useful for accelerating sedimentation rate, and provides relative stability information, but can potentially destroy flocculate structure.
Rheological Assessment: Used to measure viscosity at various shear rates and provide insights into the structural changes that occur during storage; useful for routine quality control measures
Temperature Cycling: Helps assess the stability against temperature fluctuations through cycling between high and low temperatures. Useful for assessing crystal growth, by measuring particle size for example.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the key concepts and physical properties of pharmaceutical suspensions. This quiz covers the definitions, classifications based on particle size, and unique applications in the parenteral context. Test your knowledge on the importance of stability and sterility in drug formulations.