Flashcards in The Solid State Deck (19)
Why are solids important In the pharmaceutical sector? (2)
- many medicines are in solid dosage form
- solid properties affect the importance of medicines by dictating key performance parameters like solubility
What happens with Norvir?
It was a drug which failed the dissolution test due to the solid form due to formation of crystals which affected its dissolution.
Solid properties (3)
resist changes to shape and volume
physical state of matter
Types of solid forms: (2)
Crystalline - order of the arrangement is the same throughout the whole structure
Amorphous - order of the arrangement of molecule differs through the structure.
Crystalline solid facts (4)
made up for repeating units
defined geometric shape
sharp melting point
have long and short-range order
Amorphous solid facts (4)
no sharp melting point but have a glass transition temperature (transition to semi-solid)
irregular molecule arrangement
thermodynamically less stable than crystals
only have short-range order
How does a X-ray diffraction shows us if a solid is crystalline or amorphous?
crystalline - distinct sharp peaks
amorphous - broad trace with no distinct sharp peaks
This is possible because..
when crystalline solids can take many different shapes/arrangements
this is possible because of multiple functional groups
Polymorphism doesn't affect...
e.g. molecular weight/ pKa
These will be the same no matter the arrangement.
Examples of polymorphism
Graphite is a polymorphic compound of Diamond.
What is Transformation?
One solid form can spontaneously convert to another depending on favourable environmental conditions.
Most stable and least stable solid structure?
Most - crystalline
Least - amorphous
Most soluble and least soluble solid structure?
Most - amorphous
Least - crystalline
Stability depends on...
The greater the stability, the lower the...
An example of a drug who presents polymorphism:
stable, easy to crystallise but hard to compact
metastable, difficult to crystallise but easy to compact
What happens with the forms of Chloramphenicol?
mixture of alpha and beta crystals where b form is more water soluble and has greater oral bioavailability.
the more beta = absorbed quickly and more effective.
What happens to the Ritonavir in the capsule?
A new crystal type has been formed - different arrangement that they had never seen.