Week 29 / Physical Stability- two phase systems Flashcards
What does physical stability mostly refer to in pharmaceuticals, and what are common threats to it?
Physical stability mostly refers to the visual and organoleptic (sensory) appearance of a drug product.
Common threats include excessive temperatures, pH changes, moisture, and oxidation.
Changes in physical stability are often an indirect effect of chemical instability.
How are two-phase systems (like solid-liquid mixtures) related to physical stability?
Two-phase systems are more prone to physical instability due to potential changes in sedimentation, aggregation, or crystallization, which can affect the appearance and consistency of the drug product.
Flashcard Front (Question):
What is a crystal in terms of molecular arrangement?
Flashcard Back (Answer):
A crystal is a chemically well-defined solid with a high degree of order in the arrangement of atoms and molecules—like “clear ice.”
Flashcard Front (Question):
What is an ideal crystal?
Flashcard Back (Answer):
An ideal crystal is a perfect array where building blocks (atoms or molecules) are arranged in well-defined symmetries and repeated in three dimensions through translations.
Flashcard Front (Question):
What type of solid is considered the ideal solid body?
Flashcard Back (Answer):
The crystalline solid is considered the ideal solid body due to its orderly and symmetrical structure.
Flashcard Front (Question):
What is an amorphous material?
Flashcard Back (Answer):
An amorphous material has atoms and molecules arranged in a random, disordered manner.
Example: glass.
Flashcard Front (Question):
What is crystallisation from solution?
Flashcard Back (Answer):
Crystallisation is the transition of a chemical from the liquid solution state into a solid crystalline state, influenced by physical conditions like solute concentration, pressure, and temperature, which must align with the phase transition boundary.
Flashcard Front (Question):
What is a solute?
Flashcard Back (Answer):
A solute is the chemical substance that is dissolved in a liquid solution.
Flashcard Front (Question):
What is a solvent?
Flashcard Back (Answer):
A solvent is the liquid in which the solute is dissolved.
Flashcard Front (Question):
What is an anti-solvent?
Flashcard Back (Answer):
An anti-solvent is a liquid in which the solute is insoluble, and is often used to promote crystallisation by reducing solubility.
Flashcard Front (Question):
What is the key structural difference between amorphous and crystalline materials?
Flashcard Front (Question):
Which has higher thermodynamic stability: amorphous or crystalline?
Flashcard Front (Question):
Which form usually has higher solubility: amorphous or crystalline?
Flashcard Front (Question):
What is a two-phase system in the context of solids and liquids?
Flashcard Front (Question):
How does the form (crystalline or amorphous) of a solid affect a two-phase system?
Flashcard Back (Answer):
Crystalline materials have a highly ordered structure with repeating patterns.
Amorphous materials have a disordered, random arrangement of atoms and molecules.
Flashcard Back (Answer):
Crystalline forms are more thermodynamically stable, while amorphous forms are typically more energetic and unstable.
Flashcard Back (Answer):
Amorphous forms usually have higher solubility and faster dissolution rates than crystalline forms, due to their higher energy and disordered state.
Flashcard Back (Answer):
A two-phase system involves two distinct phases—typically a solid dispersed in a liquid (e.g., suspensions).
It may include a crystalline or amorphous solid in a liquid medium.
Flashcard Back (Answer):
Crystalline solids may settle more uniformly but dissolve more slowly.
Flashcard Front (Question):
What is supersaturation in the crystallisation process?
Flashcard Back (Answer):
Supersaturation is when a solution contains more solute than it can normally dissolve. It can be achieved by:
Cooling
Evaporation
Addition of an anti-solvent
Addition of a precipitant
Flashcard Front (Question):
What are the basic processes involved in crystallisation from a solution?
Flashcard Back (Answer):
Supersaturation
Nucleation (homogeneous or heterogeneous)
Crystal growth
Flashcard Front (Question):
What is nucleation in crystallisation?
Flashcard Back (Answer):
Nucleation is the initial formation of a small crystal mass (called nuclei), which serves as the starting point for crystal growth.
Flashcard Front (Question):
What is homogeneous nucleation?
Flashcard Back (Answer):
Homogeneous nucleation occurs when pure solute molecules spontaneously form crystal nuclei without impurities.
Flashcard Front (Question):
What is heterogeneous nucleation?
Flashcard Back (Answer):
Heterogeneous nucleation involves crystal formation around impurities or seed crystals, which catalyse the process.
Flashcard Front (Question):
What happens during crystal growth?
Flashcard Back (Answer):
In crystal growth, more solute molecules add to the existing nuclei, forming larger crystals.
Flashcard Front (Question):
Why is the solid state important in pharmaceutical formulations?
Flashcard Front (Question):
Which pharmaceutical properties are influenced by the solid state of a drug?
Flashcard Front (Question):
How does polymorphism affect drug formulation?
Flashcard Front (Question):
What is the effect of particle size in the solid state of a drug?
Flashcard Back (Answer):
Because it affects key properties like:
Shape
Particle size
Polymorphism
Hydration
Solvation
These influence the drug’s performance and manufacturability.
Flashcard Back (Answer):
Flowability
Tableting
Dissolution
Bioavailability
Disintegration
Route of drug administration
Flashcard Back (Answer):
Different polymorphic forms of a drug may have different solubilities, stabilities, and bioavailability, impacting efficacy and shelf life.
Flashcard Back (Answer):
Smaller particle size increases surface area, which can enhance dissolution rate and bioavailability.
Flashcard Front (Question):
What is a supercritical fluid?
Flashcard Front (Question):
What gas-like and liquid-like properties do supercritical fluids have?
Flashcard Front (Question):
Why do supercritical fluids have a high dissolution capacity?
Flashcard Front (Question):
Why do supercritical fluids allow rapid mass transfer?
Flashcard Front (Question):
How are supercritical fluids related to two-phase systems?
Flashcard Back (Answer):
A supercritical fluid is a substance that exists above its critical temperature and pressure, where it exhibits unique properties between those of a gas and a liquid.
Flashcard Back (Answer):
Gas-like properties: low viscosity and high dispersion
Liquid-like properties: high density
Flashcard Back (Answer):
Because of their high density, which allows them to dissolve many substances effectively.
Flashcard Back (Answer):
Due to their low viscosity, enabling faster diffusion and mass transfer.
Flashcard Back (Answer):
In processes involving supercritical fluids, two-phase systems (like solute-solvent or drug-carrier interactions) can transition more efficiently, enhancing drug formulation and particle engineering.
What does the Rapid Expansion of Supercritical Solutions (RESS) technique involve?
RESS involves the precipitation of a solute from the
supercritical fluid by reducing the solvent density
through a rapid expansion.
What does the Supercritical Anti-Solvent (SAS) technique?
In SAS technique, A solution is sprayed into the
supercritical fluid, which acts as anti-solvent for
the drug. The drug particles precipitate and the
solvent of the solution is extracted into the
supercritical fluid
