Pharmacokinetics Flashcards
What does phase 1 of drug metabolism in the liver involve?
Cytochrome P450 enzymes in the liver (very versatile enzymes) strip groups off the drugs to expose their functional groups and make them more reactive. This involves oxidation, reduction, hydrolysis, deamination.
What does phase 2 of drug metabolism involve?
The molecule is conjugated to glucuronic acid, amino acids (e.g glycine), or sulphuric acid, so that it is water soluble and can be excreted by the kidney.
What is the first pass effect?
Drugs taken orally are absorbed into the portal vein and taken to the liver before entering the whole circulation, so a fraction of the drug is already inactivated and metabolised before it reaches the rest of the circulation.
What is the difference between a partial agonist and a full agonist?
A partial agonist binds to the receptor but only has partial efficacy, so has a decreased tendency to activate the receptor (can’t produce maximal response even if higher concentration applied).
What is the dose ratio?
The dose ratio is defined as the ratio by which the agonist concentration has to be increased in the presence of the antagonist in order to restore a given level of response.
What is an irreversible antagonist?
Ligand that binds covalently to the binding site on the receptor, and so can’t be displaced by either competitive ligands or washing.
Give three examples of drug targets.
G protein coupled receptors, ion channels, receptor tyrosine kinases.
What is tachyphylaxis?
Rapidly diminishing response to successive doses of a drug, rendering it less effective over time. The effect is common with drugs acting on the nervous system.
