Suspension Assignment 1 PDF

# Assignment Date: 28-10-2024 Submitted To: Dr. Omer Mahmood Submitted By: Kiran Fatima Roll Number: 114 Subject: Dosage Form Science Due Date: 28th Oct, 2024 Topic: Suspensions, Its Classification and Theoretical Considerations ## Suspensions ### Definition A pharmaceutical suspension is a coarse...

# Assignment Date: 28-10-2024 Submitted To: Dr. Omer Mahmood Submitted By: Kiran Fatima Roll Number: 114 Subject: Dosage Form Science Due Date: 28th Oct, 2024 Topic: Suspensions, Its Classification and Theoretical Considerations ## Suspensions ### Definition A pharmaceutical suspension is a coarse dispersion in which the internal phase (therapeutically active ingredient) is dispersed uniformly throughout the external phase. **E-g:** * Antacid oral suspension * Antifungal oral suspension * Antibacterial oral suspension * Anticonvulsant oral suspension * Antihelmentic oral suspension ### Types Suspension are divided into many types on different basis; ### A. Based On General Classes | Suspension | Definition | Examples | |---|---|---| | Oral | Suspension that is intended for administration by mouth. | Paracetamol Suspension | | Externally Applied | Suspension intended for application on the skin. | Calamine Lotion | | Parenteral | Suspension that is intended for injection into the body via routes other than digestive tract ie, intravenous or intramuscular. | Insulin Zinc Suspension, Procaine penicillin G suspension | ### B. Based On Proportion of Solid Particles | Suspension | Definition | Examples | |---|---|---| | Dilute Suspension | Suspension in which the concentration of the active ingredient is low compared to the volume of the liquid vehicle (2-10% w/v solid) | Cortisone acetate, Predinisolone acetate | | Concentrated Suspension | Suspension in which the concentration of active ingredient is high or equal as compared to the volume of the liquid vehicle (50% w/v solid) | Zinc Oxide Suspension | ### C. Based on Size of Solid Particles | Suspension Type | Definition | Examples | |---|---|---| | Colloidal Suspension (<1μ) | Suspensions having particle sizes of suspended solid less than one micron are called colloidal suspension. | Doxorubicin, Amphotericin B | | Coarse Suspension (>1μ) | Suspensions having particle sizes of greater than about one micron in diameter are called coarse suspension. | Milk of magnesia, Barium sulphate | | Nano-Suspension (<1nm) | Suspensions that are colloidal dispersion of nanosized drug particles stabilized by surfactants. | Straconazole nanosuspension, Amphotericin B nanosuspension | ### D. Based On Electrokinetic Nature Of The Solid Particles * Flocculated Suspension * Deflocculated Suspension ## Flocculated Suspension **Definition:** In flocculated suspension, particles come in contact with each other and form loose aggregates. ## Deflocculated Suspension **Definition:** In deflocculated suspensions, individual particles exist as sediment which is closely packed at the bottom. ### Floc Formation **Flocs are formed.** **Hardcake is formed at the bottom of the container.** ### Sedimentation Rate * Flocs cause increase in sedimentation. * It has slow sedimentation. ## Redispersion * It can be easily redispersed * It does not redisperse easily # Theoretic Consideration of Suspension Theoretical considerations refer to the underlying principles, assumptions and frameworks that guide research or analysis in a particular field. Theoretic considerations of suspensions include; 1. Particle Size Control 2. Wetting 3. Sedimentation 4. Brownian Movement 5. Electrokinetics 6. Aggregation ## 1. Particle Size Control * It must be reduced within a critical range. * Too large or too small particles should be avoided. * Fine particles will form hardcake at the bottom. * Large particles settle faster at the bottom of the container. * Particle size >5μ impart gritty texture to the product and cause irritation in injections. * Particles >25μ may block the needle. ## 2. Wetting * **Hydrophilic materials** (Talc, MgCO3, ZnO) are easily wetted by the water. * **Hydrophobic materials** (sulphur, charcoal) are not easily wetted by the ais due to the layer of adsorbed ais on the surface. * Thus, partides even with high density float on the surface of liquid until the layer of adsorbed ais is displaced. * The use of wetting agent allows the removal of adsorbed ais on the surface and easy penetration of the vehicle into pores. ## 3. Brownian Movement * It prevents sedimentation by keeping dispersed material in a random direction. * It depends upon: * Density of dispersed phase * Density of dispersion medium * Viscosity of dispersion medium * The kinetic bombardment of the particles by the molecules of suspending medium will keep the particles suspending provided that their size is below critical radius (r). * Brownian movement can be observed. * If particle size is about 2-5mm. * When the density of particle and viscosity of the medium are favorable. ## 4. Sedimentation * Sedimentation means the settling of partides or floccules occur under gravitational force in liquid dosage form. * Velocity of sedimentation is expressed by Stoke's equation: $V_{sed} = (ρ_s - ρ_o)d^2g/18η_o$ where, * ρ_s = density of dispersed phase * ρ_o = density of dispersion medium * d = diameter of the particle * g = gravitational acceleration * η_o = viscosity of dispersion medium * V_sed = velocity of sedimentation ## Limitations of Stoke's Equation * It applies to: * Spherical particles in a very dilute suspension (ρ_s < 0.5). * Particles which freely settle without collision. * Partides with no physical or chemical attraction ## Sedimentation Parameters ### i) Sedimentation Volume (F) * Sedimentation volume is a ratio of the ultimate sediment (V_u) to the original volume of sediment (V_o) before settling. * F = V_u / V_o * V_u = final or ultimate volume of sediment * V_o = original volume of suspension before settling. * F has values ranging from less than one to greater than one. * When F<1, V_u < V_o * When F=1, V_u = V_o * The system is in flocculated equilibrium and show no clear supernatant on standing. * When F > 1, V_u > V_o * Sediment volume greater then the original volume due to the network of flocs formed in the suspension. ### ii) Degree of Flocculation (β) * It is the ratio of the sedimentation volume of the flocculated suspension (F) to the sedimentation volume of the deflocculated suspension (F_oo). * β = F/F_oo * β = (V_u/V_o) Flocculated / (V_u/V_o) Deflocculated * When β = 1, then flocculated suspension is equal to deflocculated suspension. ## 3. Electrokinetics Properties ### i) Zeta Potential * Zeta potential is defined as the difference in potential between the surface of the tightly bound layer (shear plane) and electroneutral region of the solution. ## Application * Zeta potential has application in maintaining the stability of systems containing dispersed particles. * If zeta potential is reduced below a certain value, the attractive forces exceeds the repulsive forces and particles come together. * This procen is called flocculation. ## 4. Aggregation ### I. Flocculated Suspensions * In flocculated suspension, flocs (aggregates) will cause increase in sedimentation rate due to increase in size of sedimenting partides. * Hence, flocculated suspensions sediment more rapidly. ### II. Deflocculated Suspensions * In deflocculated suspensions, individual particles are settling. Hence rate of sedimentation is slow which prevent entrapping of liquid medium which make it difficult to redisperse by agitation. The larger particles settle first and smaller remain in supernatant liquid—This phenomenon is called "caking" or "claying".