Pharmacokentics : Drug Absorption Flashcards
What are the basic concepts of pharmacology? (4)
The science of chemicals (drugs) that interact with the body
Biochemical/physiological effects on a cell, tissue or organ
Pharmacokinetics
Pharmacodynamics
What are the basic concepts of therapeutics? (4)
Treatment of an animal patient
Preventing/combating disease
Alleviating pain/injury
From the Greek term therapeutikos meaning “to serve”
What are the basic concepts of Pharmacokinetics? (5)
The way the body affects the drug with time :
1 - Absorption
2 - Distribution
3 - Metabolism
4 - Excretion
What are the basic concepts of drug absorption? (4)
How a drug reaches the circulation from point of entry
1 - Crossing of membranes
2 - I/V drugs avoid the absorption process
3 - Passive diffusion – how most drugs travel around the body
Define Passive diffusion (3)
Passing through the lipid (fat) layer of the cell
Lipid solubility
Concentration gradient required
What are Ion channels? (4)
Selective pores in the cell membrane
Allow the ready transfer of ions down their electrochemical gradient.
Can be either -
Voltage gated
Ligand gated
Define Active Transport (4)
used to transfer substances against their concentration gradients.
Utilise special carrier molecules in the membrane
Requires metabolic energy (ATP).
common example of such a system is the sodium pump.
Define the term Bioavailabiltiy (1)
the proportion of administered drug reaching systemic circulation
Identify factors which affects oral drug absorption (6)
Formulation of the drug (hydrophilic vs lipophilic, ionised vs non-ionised)
Stability to acid and enzymes
Gut motility
Food in the stomach
Degree of first-pass metabolism
Health status of the animal
Explain oral absorption (4)
Mouth —-> small intestines where it is absorbed
Must pass accross gastrointestinal mucosa
Enters hepatic portal circulation —-> Liver
* First pass effect
What does First pass effect mean? (3)
Drugs given orally are usually absorbed in the small intestine
Arrive at the liver where they may be extensively metabolised
Some drugs can’t be administered orally
Identify factors affecting parenteral absorption (4)
Drug formulation
- water soluble drugs mix with body fluids more rapidly
Blood supply
Health status of the animal – cardiovascular disease?
Fitter animals have a faster absorption rate
