ACTIVITY 6: PREPARATION OF ALLOPURINOL ORAL SUSPENSION

>0.5 µm

Coarse Dispersions (Suspensions and Emulsions)

Cold solutions

Coarse Dispersions also known as?

1nm – 5µm

Colloidal dispersions (Gels and Magmas).

<1nm

Molecular dispersions (true solutions).

>0.5 mcm

SUSPENSION?

Suspension

Two-phase system consisting of finely divided solid dispersed in a solid, liquid or gas.

• Settle slowly, easily dispersed with gentle shaking.

• Particle size should remain fairly constant in long periods of undisturbed standing.

• Pour slowly and evenly in the container.

Properties of Suspension

Caking

Problem in Suspension

1. Micropulverization

2. Fluid energy grinding/Jet milling/ Jet micronizing

3. Spray-drying

Particle Size Reduction in Suspension (3)

1. Comminute

2. Wetting agent

3. Suspending agent

4. The product is brought to final volume using the vehicle

5. Homogenize

GENERAL STEPS IN THE MANUFACTURE OF PHARMACEUTICAL SUSPENSIONS (4)

Wetting agent

Levigation to displace air in the crevices of the particle to make drug penetrable (surfactants with HLB 7-9, hydrophilic colloids, alcohol, glycerine, glycols).

Suspending agent

Dispersed in the vehicle and added to the melted powder by geometric dilution.

1. Polysaccharides: Acacia, tragacanth, alginic acid, xanthan

2. Cellulose derivatives: Methyl-, hydroxyethyl-, Na carboxymethyl- (carmellose Na), Avicel

3. Hydrated silicates: Bentonite, Veegum (Mg Al silicate), hectorite

4. Misc: Carbomer, colloidal silicon dioxide, PVP

Types of Suspending Agents: (4)

Homogenizer

• Homogenizer

• Colloid mill

1. Suspending agents

2. Wetting agents

3. Flocculating agents

4. APIs

5. Liquid vehicle

6. Buffers

7. Preservatives

8. Colorants, flavors, and fragrances

GENERAL FORMULATION OF SUSPENSIONS (8)

Suspending agents

Viscosity-increasing agents used to reduce sedimentation rate of particles in a vehicle.

1. tragacanth

2. acacia

3. celluloses

4. bentonite

5. magma

6. veegum

7. agar

8. carrageenan

9. gelatin

10. kaolin.

Examples of suspending agents in Suspensions (10)

Wetting agents

Displace air from crevices of hydrophobic solids to allow penetration of water.

Flocculating agents

Reduce the electrical barrier between the particles of the suspensoid and forming a bridge so as to link them together (decrease zeta potential causing aggregation to avoid formation of cake).

1. surfactants

2. glycerin

3. PP

4. PEG

5. syrup

Examples of Wetting agents in Suspension (5)

1. Electrolytes (NaCl, KCl)

2. surfactants

3. Polymers

Examples of Flocculating agents in Suspension (3)