Drug Absorption Flashcards
Four basic factors that determine drug pharmakinetics
Absorption
Distribution
Metabolism
Elimination
Define absorption
The process of movement of uncharged drug from site of administration to the systemic circulation
How quickly the drug will get into the system at a sufficient amount
Tmax
Maximum concentration achieved (peak concentration)
Cmax
All the amount of drug that has gone into systemic circulation
Area Under Curve (AUC)
A drug given IV has _____ Bio-availability
100%
The amount of drug in circulation
Bioavailability
Factors that effect bioavailability
Formulation
Ability of drug to pass physiological barriers
Gastrointestinal effects
First pass metabolism
First Pass Metabolism
Drugs that are absorbed via the GIT are circulated to the liver first via the hepatic portal vein
The liver acts as a filter and only part of the drug is circulated systemically
A physiological barrier
Transport membranes
Actions across transport membranes
Passive diffusion Filtration Bulk flow Active transport Facilitated diffusion Ion-pair transport Endocytosis
Most drugs completely ionise in water (True or False)
False
Only non-ionised (non-polar) drugs diffuse across the membrane (True or False)
True
Most drugs are not weak acids or bases (True/False)
False
Does the degree of ionisation depend on the PH of the environment as well as the drug
Yes
An acidic drug concentrated in the compartment with High ph (alkali)
Ion-trapping
Henderson-Hasselbalch equation
The relationship between the local PH and the degree of ionisation
The more positive the value of Pka is the smaller the extent of dissociation
True
The ability of a drug to diffuse across a lipid barrier
Lipid-water partition coefficient
Facilitated diffusion (5)
Along conc. gradient Requires carriers Saturable Mixed order kinetics Monosaccharides, amino acids and vitamins
Other routes of drug administration
Subcutaneous/intramuscular Sublingual, buccal Rectal Inhalation/Nasal Transdermal
Taking a higher does will increase the ______ but not the ________
Cmax and Tmax
Therapeutic index
The relationship between the doses of a drug that causes lethal or toxic effects with the dose that causes therapeutic effects
Therapeutic Range
Above this range the drug is not effective
