1. Materials Science

What is a medicine and what is a solid particle?

• A medicine is a formulated drug product containing an active drug substance

• A solid particle is a solid drug form made up of countless drug molecules

What are the key differences between amorphous & crystalline forms of a drug?

• Amorphous:

  • Fast dissolution

  • Temperature not important

  • Stable without water

  • Collapses in presence of water

  • Has a critical formation temperature (Tg)

• Crystalline:

  • Slow dissolution

  • Temperature important

  • Stable without & with water

  • Has a melting temperature (Tm)

  • Can have different crystalline arrangements (habits)

What is a crystalline material & unit cell?

• Crystalline material → molecules arranged in a repeating pattern

• Unit cell → smallest repeating arrangement of molecules in the crystal

How is a unit cell described?

• By side lengths: a, b, c

• By angles between sides: α, β, γ

Give examples of types of unit cells.

• Triclinic

• Monoclinic

• Orthorhombic

• Tetragonal

• Hexagonal

• Rhombohedral

• Cubic

What is crystal habit & why is it important?

• Habit → observed shape of a crystal

• Same unit cell can form different habits

• Only 6 habits: tabular, columnar, equant, plate, blade, acicular

• Affects powder flow, compaction & dissolution