Materials and Excipients I Flashcards
What is the purpose of using different materials?
Properties of formulations can effect drug performance, quality, appearance, dosage, effect on patient
What can form from a solid?
Spider diagram
Solid > Amorphous or crystal
Crystal > Polymorphs, Solvates/hydrates or co-crystals
What is the difference between crystalline and amorphous?
Crystalline - Molecules packed in long-range order, have a mp
Amorphous - No long-range order (irregular pattern), glass transition temperature (Tg), high dissolution rate, unstable
Define glass transition temperature
Temp where 30-50 C-chains move, amorphous changes from rigid to flexible state (solid to rubbery)
Define polymorphs
Same molecule exists as two/more crystalline forms
What affects the solubility of crystals?
Anhydrates and solvates
What are co-crystals?
A crystal between two different molecules
Describe hydrates
Have lower H2O solubility than anhydrates with bonds btw H2O and drug
Why do hydrates have a lower H2O solubility?
H2O in crystal already solvating the drug so lower solubility as its already solvated
How does the drug go into solution?
If the bonds release enough energy to overcome IMF, drug goes into solution
Which properties differ between different crystals?
Mp, solubility, dissociation rates, bioavailability, stability, material prop, processibility
Name and describe a method of processing materials
Milling (Grinding):
1) Powder flows into die (mold) > Particle size affects flow
2) Compress powder granules together into tablet
What are the properties of solids?
Brittleness, toughness, surface hardness, elasticity, plasticity, ductility
What is the purpose of milling solids?
Reduces particle size which means drug dissolves better, flows better
Describe the difference between brittleness and toughness
Brittle - Easily broken on impact
Toughness - Ability to withstand impact
Define hardness
Ability to withstand scratching
Describe hardness
Measured by Mohs’ scale - Diamond is hardest, scratches everything below it
How does temperature affect hardness?
Decreasing temp increases hardness
If tablet easily scratches, coating could be removed
Define elasticity
Ability to return to its original shape after stretched
Describe elasticity
Has an elastic limit (snaps), difficult to mill as it returns to original shape, breaks flat when milled (brittle fracture)
Define plasticity
Ability to hold shape after stretched without breaking
Describe plasticity
Heating increases plasticity
When milled, absorbs energy used to crush it - wastes energy
Define ductility
Ability to be stretched by a force into thin wire
Describe ductility
Bad for milling as energy is wasted
What are the 3 methods of measuring material properties?
Compression, Tension and Rotation
Describe compression
Measures brittle/hardness of tablet - How much energy it takes/absorbs
Describe tension
Measures elasticity/plasticity - The force put in
Describe rotation
Measures liquid/gel via a rod - How much force it takes to rotate it
