Pharmaceuticals module 1 Flashcards
What is flux?
The amount of material transferred through per unit cross sectional area in unit time is denoted as the flux
What is a barrier in diffusion?
A region or a region of a system that offer resistance to mass transfer or diffusion.
What does it mean when diffusion process under conditions of steady state?
The concentration gradient does not change with time but remains steady constant
What is Fricks first law?
The flux of the material diffusing across a given plane is proportional to the concentration gradient.
What is Ficks second law?
In a volume element within the diffusion field, the RATE of concentration change is proportional to the CHANGE in concentration gradient in that part of the system.
What is ultrafiltration?
It is a process to separate macromolecules using a membrane and involves applying hydraulic pressure.
What is dialysis?
It is a separation process based in the unequal rates of passage of solutes and the solvent through a semi permeable membrane
What is haemodialysis?
It is a process through which blood is filtered specifically to exclude certain small molecules while preserving. Larger molecules.
What is diffusion?
Process of mAss transfer of individual molecules of a substance brought about by the random molecular motion and associated with a driving force such as concentration gradient.
What needs to happen in order for a reaction to occur?
A collision must occur.
The collision must be of sufficient energy to break the order of a reaction.
Be of proper orientation
What are the factors that effecting the reaction rate?
Concentration
Temperature
Presence of a catalyst
Light
What is a unimolecular reaction?
In a unimolecular reaction one molecule with a different decompose into two or more atoms/molecules
What is a bimolecular reaction?
These reactions involve two molecules. The two molecule can either
What is the ideal drug candidate?
Appropriate aqueous solubility to provide desired dose in 20mL of formulation per nostril Low Mwt smaller is better Low Dose Appropriate nasal absorption properties No nasal irritation No toxic nasal metabolites No offensive odours Suitable stability
What is heat of fusion considered as?
It is considered as the heat required to increase inter-atomic, inter-ionic or intermolecular distances and overcome intermolecular forces of attraction.
What are the unit that constitute crystal structures?
Atoms, molecules or ions.
What can be the overall shape of a crystal?
Acicular, prismatic, pyramidal and tabular.
Define polymorphism
Existence of elements or molecules in more than one crystalline form.
What are liquid crystals?
This molecular order gives rise to properties such as ability to rotate plane polarised light. Liquid crystals are systems in echo the there is some degree of molecular order while maintaining an overall fluid state.
Define the solubility of a gas
The concentration of dissolved gas when it is in equilibrium with some of the pure gas above the solution.
What are the factors affecting the solubility of a gas?
Pressure
Temperature
Addition of salts (salting out)
Chemical reactions
What are the types of membranes?
A) Membrane of dense material with straight through out pores
B) Homogenous membranes without pores
C) Cellulose membrane used in filtration processes showing intertwining nature of fibres and tortuous channels
What is the diffusion coefficient affected by?
Temperature, Pressure and nature of the solute and solvent properties
When has steady state condition been achieved?
When the RATE of change of concentration is equal to zero.
