Chapter 1: Basic concepts Flashcards
List the 2 Factors that influence drug availability
– Physicochemical properties of the drug
– Formulation Factors that affect drug release from its dosage form
List physicochemical properties of the drug ***
- Aqueous solubility
- Particle size
- Polymorphic form
- Salt form
- Dissociation constant
- Partition coefficient
- Membrane permeability
List Formulation Factors that affect drug release from its dosage form ***
- Dosage form
- Excipients
- Tablet hardness & disintegration
- Tablet coating (type of polymer)
> Inorder for a drug to undergo absorption, it must be ______ in ______ <
dissolved in fluid
– Aqueous solubility greater than ______ indicates there will be ______ in drug absorption
1% (1g/100 mL) , drug absorption
Aqueous solubility less than ______ indicates there will be a ______ in drug absorption
0.3 % (0.3g/100mL), problem
If a drug’s solubility is considered bad, What should you do ?
- Particle size reduction will increase dissolution rate, absorption, and bioavailability but does not change intrinsic solubility.
What does particle size influence?
Influences the rate at which the drug dissolved in the dissolution
A large drug particle that is reduced into a large number of small particles causes _____
Increase of total surface area
Sufrace area of spherical particles is related to
Particle size (diameter)
Formula of Surface area of spherical particles
(π)(diameter)^2
Formula of surface area g of particles
g = 6/(diameter)(density)
What percentage of drug exhibits polymorphic form?
70%
Polymorphic Form: Characteristics
- Less stable
- Greater solubility
- Faster dissolution rate than crystalline forms
What effects how cocoa butter will enter the body?
If cocoa butter is carelessly melted at a temperature exceeding its boiling point and quickly chilled this results in metastable polymorphic form of cocoa butter which will effect how coca butter will enter the body
Salt form of drug has…?
greater solubility
Why are drugs marketed as salts ?
- Monovalent salts of weak/strong acids or bases have a GREATER solubility and dissolution rate compared to free acids and bases
What is dissociation constant?
parameter of drug absorption
Define dissociation constant?
- Passageway for drug in undissociated form
What is the function of dissociation constant?
- Indicates the extent of which the drug will dissolve in it’s ionized form
What is the solubility and permeability of ionized form of drug?
-bad solubility
-good permeability
Define partition coefficient
- Absorption drug in solution by passive diffusion through a lipoidal barrier is a function of partition coefficient (C oil/C water)
Membrane permeability is based on
- Fick’s first law of diffusion
What is fick’s first law of diffusion?
Diffusion of a substance through the membrane is directly proportional to concentration gradient.
List Formulation Factors that affect drug release from its dosage form
- Dosage form
- Excipients
- Tablet hardness & disintegration
- Tablet coating (type of polymer)
What two things affect bioavailability?
-Different dosage
-Different manufactures
Dosage form can affect…?
The clinical performance of the drug
List Excipients used in Solid Dosage Form
- Binders
- Diluents
- Disintegrates
What are the functions of excipients?
- Affects the drug’s bioavailability and release from its dosage form
- Form complex with the drug → forming a portion of the drug that is unavailable for absorption
Examples of excipients
- Calcium salts
- PEG 400
- Magnesium stearate
- Amphetamine
What is an example of calcium salts?
Dicalcium phosphate
What is the purpose of calcium salts?
Used as diluent in tetracycline dosage form
