Suspensions: General introduction, Properties, Classification, Advantages and disadvantages and MCQs for GPAT, NIPER, Pharmacist and Drug Inspector exam

Suspensions: General introduction, Properties, Classification, Advantages and disadvantages and MCQs for GPAT, NIPER, Pharmacist and Drug Inspector exam

Suspensions:

The physical chemist defines the word “suspension” as a two phase system consisting of an undissolved or immiscible material dispersed in a vehicle (i.e., solid, liquid, or gas). The particles of the dispersed phase vary widely in size, from large, visible particles to colloidal dimensions, which fall between 1.0 nm and 0.5 μm in size. Coarse dispersions contain particles 10–50 μm in size and include suspensions and emulsions. Fine dispersions contain particles of smaller size, 0.5–10μm. Magmas and gels represent such fine dispersions.

Classification: Suspensions can be classified as:

1-Based on physical state:

  • Suspensions
  • Aerosols
  • Foams

2-Based on Proportion of Solid Particles:

  • Dilute suspension (2 to10% w/v solid). For example cortisone acetate, prednisolone acetate
  • Concentrated suspension (50%w/v solid). For example zinc oxide suspension

3-Based on behavior of Dispersed Phase:

  • Flocculated Suspension (Dispersed phase maybe a network of particle)
  • Deflocculated Suspension (Dispersed phase may consist of discrete particles)

4-Based on Size of Dispersed Particles:

  • Molecular Dispersion (Particle size is less than 1 nm)
  • Colloidal Dispersion (Particle size between 0.1-0.2 µm)
  • Coarse Dispersion (Particle size is greater than 0.2 µm)

5-General classification of Suspension:

  • Oral suspension (Example is Paracetamol suspension)
  • Topical suspension (Dispersed phase is in high concentration often exceeds 20% w/v. Example is Calamine Lotion)
  • Parenteral suspension (Solid Contents is between 0.5-5% w/v. Example includes Procaine penicillin G suspension)

Properties of a Suspension: A well formulated suspension should have:

  • Easy and rapid redispersion of sedimented particles for uniformity of dose.
  • No cake formation on sedimentation.
  •  Optimum viscosity for pouring.
  • Physical and chemical stability.
  • Free from gritting particles (in case of external use)

Advantages:

  • Suspension can improve chemical stability of certain drug. For example Procaine penicillin G.
  • Drug in suspension exhibits higher rate of bioavailability than other dosage forms.

Solution > Suspension > Capsule > Compressed Tablet > Coated tablet

  • Duration and onset of action can be controlled. For example Protamine Zinc-Insulin suspension.
  • Suspension can mask the unpleasant/bitter taste of drug. For example Chloramphenicol

Disadvantages:

  • Physical stability, sedimentation and compaction can causes problems.
  • It is bulky. Sufficient care must be taken during handling and transport.
  •  It is difficult to formulate.
  •  Uniform and accurate dose may not be achieved.

Multiple choice questions:

1.Suspension is a

a)one phase system

b)two phase system

c)multiple phase system

d)all of these

2.Suspension consist of an undissolved or immiscible material dispersed in a vehicle such as

a)solid

b)liquid

c)gas

d)all of these

3.Based on physical state suspensions are classified as

a)Foams

b)Dilute suspension

c)Colloidal Dispersion

d)All of these

4.Based on proportion of solid particles suspensions are classified as

a)Foams

b)Dilute suspension

c)Colloidal Dispersion

d)All of these

5.Dilute suspension have _____ concentration of solids in them.

a)2 to5% w/v

b)2 to10% w/v

c)1 to10% w/v

d)2 to20% w/v

6.Concentrated suspension have _____ concentration of solids in them.

a)2 to5% w/v

b)2 to20% w/v

c)50%w/v solid

d)70%w/v solid

7.Example of dilute suspension is

a)cortisone acetate

b)prednisolone acetate

c)zinc oxide suspension

d)a and b

8.Example of concentrated suspension is

a)cortisone acetate

b)prednisolone acetate

c)zinc oxide suspension

d)all of these

9.Based on behavior of dispersed phase suspensions are classified as

a)Flocculated Suspension

b)Deflocculated Suspension

c)Both of these

d)None of these

10.Based on size of dispersed particles suspensions are classified as

a)Molecular Dispersion

b)Colloidal Dispersion

c)Coarse Dispersion

d)All of these

11.In molecular dispersion particle size of solids is

a)less than 1 nm

b)0.1-0.2 µm

c)greater than 0.2 µm

d)none of these

12.In colloidal dispersion particle size of solids is

a)less than 1 nm

b)0.1-0.2 µm

c)greater than 0.2 µm

d)none of these

13.In coarse dispersion particle size of solids is

a)less than 1 nm

b)0.1-0.2 µm

c)greater than 0.2 µm

d)none of these

14.Which of the following is an example of oral suspension?

a)Paracetamol suspension

b)Calamine Lotion

c)Procaine penicillin G suspension

d)All of these

15.Choose the correct order of bio availability in the following dosage forms.

a)Suspension > Solution > Capsule > Compressed Tablet > Coated tablet

b)Solution > Suspension > Coated tablet > Compressed Tablet > Capsule

c)Solution > Suspension > Capsule > Compressed Tablet > Coated tablet

d)Solution > Coated tablet > Capsule > Compressed Tablet > Suspension

Solutions:

  1. b)two phase system
  2. d)all of these
  3. a)Foams
  4. b)Dilute suspension
  5. b)2 to10% w/v
  6. c)50%w/v solid
  7. d)a and b
  8. c)zinc oxide suspension
  9. c)Both of these
  10. d)All of these
  11. a)less than 1 nm
  12. b)0.1-0.2 µm
  13. c)greater than 0.2 µm
  14. a)Paracetamol suspension
  15. c)Solution > Suspension > Capsule > Compressed Tablet > Coated tablet

References:

  1. Lachman/Lieberman’s The theory and practice of industrial pharmacy, 4th edition, page no. 655
  2. Remington Essential of Pharmaceutics, 1st edition 2013, page no. 458.
  3. Ansel’s Dosage Forms and Drug Delivery Systems, 10th edition, page no. 446-448.

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