Introduction to medicinal products - dissolution Flashcards
What is the features of a pure drug?
Drug substance
Active pharmaceutical ingredient
medicinal agent
active principle
drug powder
drug
What is features of drug and excipients?
Drug product
Medicinal product
Formulations
Medicine
Drug
- May include the primary and secondary packaging
what is pharmaceutics?
The process of turning a drug substance into a medicinal product to be used safely and effectively by patients (formulation)
What are the 3 pillars of pharmaceutics?
- Bio-physico-chemical properties of drug product and drug substance
- bio pharmaceutical considerations
- patient centres, therapeutic considerations
What is the order of onset time of drug routes
Intravenous
Intramuscular
Sub-cutaneous
How can dissolution rate be measured?
Noye-whitney equation
What are some factors effecting pharmaceutics?
- Partition coefficient (Log P): ability to diffuse across membranes
- Stability: chemical, physical and biological
- oranoleptic properties
-powder properties
What molecules can be absorbed immediately?
Drugs in solution because molecules are dispersed eg liquid paracetamol has more rapid onset than tablets
What is a solution?
a mixture of two or more components that form a single, homogeneous phase
What is a solution?
a mixture of two or more components that form a single, homogeneous phase
what is dissolution?
a process by which a solid dissolves in a solvent to produce a solution
what is the solubility of a substance?
the amount that goes into a solution when equilibrium is established between the solute in solution and excess (undissolved) substance
What happens to a tablet during drug absorption?
Tablet has slow dissolution rate, it begins to disintegrate into granules (dissolution is intermediate) and then deaggregation (dissolution is fast) occurs to form fine particles. When drug is in solution it is able to be absorbed and can enter the bloodstream
What are the symbols of the noyes whitney equation and their meaning?
dm/dt - rate of dissolution of drug particles
D = diffusion coefficient
A = effective SA of drug particles
h= thickness of the diffusion layer
Cs= saturated solubility
C = concentration in the bulk solubility
What are the key factors of dissolution rate?
Particle size and drug solubility
What happens to dissolution rate if you reduce particle size
Increases
What happens to dissolution if you decrease porosity?
Decrease
What happens if the thickness of boundary layer increases (reduced mixing)?
Dissolution decreases
what happens to dissolution if you increase drug solubility
Increases
what happens to dissolution if you increase drug solubility
Increases
What happens to dissolution if you decrease diffusion coefficient (increasing viscosity)
Decreases
What are other components affecting dissolution?
Stomach contents (food components, pH buffer capacity)
GI motility (transit/emptying of stomach, gastrointestinal secretions)
What are other components affecting dissolution?
Stomach contents (food components, pH buffer capacity)
GI motility (transit/emptying of stomach, gastrointestinal secretions)
What does pharmacopeia BP and EP mean (book with drugs and there use as medicines)
British pharmacopeia and European pharmacopeia
What is the solution process?
- drug molecule is removed from its crystal
- a cavity from the molecule is created in the solvent
- the drug molecule inserts into this cavity
What are factors effecting solubility ?
- Temperature (collision theory- more energy, more rapid solubilisation)
- Molecular structure ( shape and SA, Hydrophobicity and degree of ionisation)
- Nature of solvent (PH and solvents, solubilising agents)
- Crystal characteristics
How does a higher temperature affect stability of a crystal?
Higher temp = more stability (less likely to break down)
How does large surface areas affect solubility ?
Lowers it
How does polar/non-polar groups affect solubility?
Polar groups increase solubility
non-polar groups decrease it
how does ionisation effect solubility?
Increases it
What is partitioning of drugs?
Due to a difference in solubility in different phases the drugs will partition between 2 solvents (2 phases of polar and non-polar of a drug)
eg. between aqueous and lipid phases
antibiotics partitioning into microorganisms
what is log P?
The partition coefficient
Measure of lipophilicity/hydrophilicity - unionised
What does a log P greater than 0 and less than 0 mean,
Log P > 0; lipophilic
Log P <0; hydrophilic
What are the different types of solids?
- Ionic solids
- Molecular solids
- Molecular salts
What is polymorphism?
When compounds can crystallise out of solution into a variety of different habits depending on the conditions ( usually have the same structure but can also crystallise with different structures)
What are features of the DVLO theory?
The repulsive energy is electrostatic forces
The attractive energy is vdw forces
The theory helps predict stability of pharmaceutical suspensions
The primary minimum leads to coagulation
