Pharmacokinetics Flashcards
The journey of a drug through the body
ADMINISTRATION A=Absorption D=Distribution M=Metabolism E=Excretion REMOVAL
Major routes of drug administration
- dermal
- intramuscular
- subcutaneous
- intraperitoneal
- intravenous
- inhalation
- ingestion
Enteral routes of drug administration
VIA GI TRACT
-ingestion
Parenteral routes of drug administration
OUTSIDE GI TRACT
- dermal
- intramuscular
- subcutaneous
- intraperitoneal
- intravenous
- inhalation
Methods of drug molecule movement
- bulk flow transfer (in bloodstream)
- diffusional transfer (molecule by molecule over short distances)
Compartment classification
AQUEOUS ENVIRONMENT (eg: blood, lymph, ECF)
Barrier classification
LIPID ENVIRONMENT (eg: cell membranes)
First pass metabolism
Rapid uptake and metabolism of drug by liver, immediately after enteric absorption and before it reaches the systemic circulation (>60% of drug removed by liver so greatly reduces drug bioavailability)
-drug examples undergoing first pass metabolism: morphine, lidocaine, diazepam, propranolol
Enterohepatic circulation
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Drug/biological half-life
LINKED TO METABOLISM/EXCRETION
-time taken for the concentration of drug (in blood/plasma) to fall to half its original value
Apparent volume of distribution
LINKED TO DISTRIBUTION
- volume in which a drug appears to be distributed
- indicator of distribution pattern
Bioavailability
LINKED TO ABSORPTION
-proportion of administered drug available within the body to exert its pharmacological effect
Drug clearance
LINKED TO EXCRETION
- volume of blood/plasma cleared of a drug per unit time
- related to volume of distribution and rate of drug elimination
- if clearance involves several processes, total clearance is the sum of these processes
Major routes of drug excretion
- kidney
- liver
Factors influencing drug distribution
- regional blood flow
- extracellular binding
- capillary permeability
- localisation in tissues
