Physicochemical properties of drugs Flashcards
(36 cards)
What are physicochemical properties?
Fundamental characteristics of drugs that influence their behavior in formulations and biological systems.
Why are physicochemical properties important in pharmacy?
They affect drug formulation, solubility, bioavailability, membrane permeability, and clinical effectiveness.
Name five physicochemical properties of drugs.
Molecular weight, solubility, boiling/melting point, partition coefficient (log P), and particle size.
What is the partition coefficient (log P)?
A measure of a drug’s lipid solubility, influencing membrane permeability.
Define solubility.
The maximum amount of solute that can dissolve in a solvent under specific conditions.
What is dissolution?
The process by which a solid drug dissolves in a solvent.
What factors affect solubility?
Lipophilicity (log P), molecular size, pKa, crystal lattice energy, and solvent properties.
How does molecular size affect solubility?
Larger molecules require larger solvent cavities, decreasing solubility.
How much water is required to dissolve a very soluble substance?
<1 mL.
What is the difference between “slightly soluble” and “practically insoluble”?
Slightly soluble requires 100-1000 mL of water, while practically insoluble requires >10,000 mL.
What is the difference between crystalline and amorphous solids?
Crystalline has an ordered molecular structure and sharp melting point, while amorphous lacks order and is generally more soluble.
Why are amorphous forms preferred in pharmacy?
They have higher solubility and dissolve more easily
What is polymorphism in drugs?
The existence of different crystalline forms of the same drug, affecting solubility and stability.
What is the difference between enantiotropic and monotropic polymorphs?
Enantiotropic can convert between forms under different conditions, while monotropic has one stable form.
Why are metastable polymorphs often preferred?
They dissolve faster and have higher bioavailability.
What are crystal hydrates?
Crystalline drugs that incorporate water molecules.
How do hydrates compare to anhydrous forms in solubility?
Hydrates have lower solubility and higher melting points.
Which is more soluble: monohydrate or anhydrous drug?
Anhydrous.
What is crystal lattice energy?
The energy required to separate molecules or ions from a solid crystal.
How does lattice energy affect solubility?
Higher lattice energy means lower solubility.
What factors influence drug dissolution rate?
Wettability, particle size, porosity, solvent properties, and excipients.
How does particle size affect dissolution?
Smaller particles increase surface area, enhancing dissolution rate.
What role do surfactants play in dissolution?
They reduce surface tension and improve wettability.
What does the Noyes-Whitney equation describe?
The rate at which a drug dissolves.
