Pharmacology 2- ADME Flashcards
How can drugs be given
Orally
intravenously
Directly into the bloodstream
at the local site of application
What is the route of a drug
Administeration
distribution
metablosism
excretion
What does ADME depend on
route of admisntration physicochemical prpteotoes of the drug drug structure molecular weight lipohpllic ionisation
What are the physiological variables
pH of site presence of food surface area mesenteric blood flow gastric emptying
What is bioavailability
% of admisntered dose which reaches the systemic circulation as an unchanged drug.
What does distribution depend on
Molecular size
ability to cross membranes
binding to plasma proteins.
As drugs such as
Heparin have a high molecular weight
Warfarin is 99% bound to plasma proteins
How does elimination occurs
renal excretion
liver metabolism
chemical transformation
What are the 2 types of compounds that are not metabolised
small water soluble molecules
some complex carbs
What is extensively metabolised
lipophilic drugs
as if metabolism didn’t occur then these would just continue to be recycles through gloemrus reabsorption.
What are the 3 pathways of drug metabolism
phase 1- Functionalisation reactions
phase 2- conjugation reactions
phase 3- formation of xenobiotic
What are the principle chemical reactions that ca occur in phase 1 metabolism
oxidation reduction hydrolysis hydration isomerisation
How does phase 1 go to phase 2
Additon of a polar group
catalysed by transferases
cofactor donor
What are the properties of drug metabolising enzymes
low substrate specificity Low reaction specify lower catalytic rates substrates usually lipophilic enzymes inducible
What 2 subcellualr compartments in the liver does drug metabolism occur
cytosol
SER
What is terfenadine and how is it metabolised
antihistamine drug
metabolised via cytochrome P450 in the liver to generate fexofendine.
T is toxic
