Lecture 9- Particle Sizing I

Question 1

Particle dimensions; why is it important?

Answer 1

Particle size= influences physical properties of pharmaceuticals (smaller particles dissolve more rapidly than larger ones)

-powder flow during handling & manufacturing
-powder mixing
-dissolution
-aerosol deposition
-stability
-safety and efficacy

Question 2

Decreasing particle size

Answer 2

Important when dissolution is the rate limiting step
*Milling helps you achieve this^

Particle size decreases whereas dissolution rate + bioavailability increases
Examples; tetracycline, aspirin, digoxin, sulphonamides and dicoumarol

Question 3

Stability

Answer 3

Stability of emulsions + suspensions depends upon the particle size

Forces between colloidal particles = affected by particle size

Settling rate of larger particles = depends on particle size + density

Particle size effects= flow properties, dose uniformity, formulation and bio-availability

Question 4

Measuring particle size

Answer 4

Maths; slide 15-16

Question 5

Calculating projected area diameter

Answer 5

Slides 18-21

Question 6

Particle size distribution

Answer 6

Population consisting of spheres/equivalent spheres with uniform dimensions = monodispersed

Unusual for particles to be completely monodispersed since there are different equivalent diameters

Therefore we find out the characteristics of the average particle and draw a histogram; slides 24-28