solids

Question 1

describe the organisation of constituents in solids

Answer 1

1. immobile solid: crystalline, has orientation and periodicity
2. Mobile 2D Smectic, rotate 1 axis: orientated and arranged in equispaced planes, with no periodicity within planes
3. mobile 3D nematic, rotated 1 axis: orientated with no periodicity

Question 2

what are major characteristics of solids

Answer 2

1. almost no kinetic energy (more stable)
2. structural rigidity, resist deformative forces
3. organised as crystals or amorphous solids

Question 3

why are most drugs delivered via solid dosage forms?

Answer 3

1. when dry, does not promote microbial growth
2. chemically more stable
3. flexible, single or multiple chemical compounds
4. ease of handling and convenient to bring around
5. lower bulk volume

Question 4

explain polymorphism

Answer 4

the ability of solid to exist in more than one form or crystal structure, with varying crystal packing

Question 5

explain characteristics of polymorphism

Answer 5

polymorphism exist as solids form different polymorphs in order to minimise their crystal lattice energy under specific thermodynamic conditions

Question 6

explain importance of polymorphism in pharmaceutics

Answer 6

as it can significantly influence variety of API properties including flowability, tableting, dissolution rate, solubility, stability and even biological performance including efficacy and toxicity

Question 7

describe the method to differentiate polymorphs

Answer 7

1. X ray diffractometry (standard)
2. melt behavior
3. Raman spectroscopy
4. infrared spectroscopy
5. nuclear magnetic resonance spectroscopy