elementary drug metabolism Flashcards
drug metabolism
enzymatic conversion of the drug to another chemical entity
what is the msot important drug metabolising organ
liver
what other organs also ocntribute
kidney gut mucosa and lungs and skin
when is bioavailabilty reduced
when administered orally
bioavailability
amount of drug that eventually reaches systemic circulation of an administered dose of the drug
quantity reaching systemic circulation /quantity adminsitered
where doe the phases of metabolism occur
in the liver
where are hepatic drug metabolizing enzymes
embedded in smooth endoplasmic reticulum of the liver hepatocytes
which cross plasma membrane to be metabolised more readily
non polar as can cross membrane more readily
phase 1 metaboism
change in the drug by oxidation reduction or hydrolysis to form a chemically reactive metabolite that can be active/ toxic
what is the oxidation phase accomplished by
cytphcrome p450 enzymes
what occurs during the oxidation phase
drug molecule incorporates one atom of 02 to the drug to form a hydroxyl group
role of cytoplasmic enzymes
can metabolise the durg
what are susceptible to hyrolysis
ester and amide bonds
what can phase 1 produce
harmful metabolites during oxidation
what are cytochrome p450 enzymes
membrane bound haem proteins
genetics of p450
some poeple lack such acitity leading to higher drug plasma levels
some have higher leading to lower plasma levels.. reduced drug action
phase 2 reaction
involve the combination of the dryg with one of the several polar molecules to form a water soluble metabolite; conjugation
what terminates all biological acitvty
phase 2 reactions
conjugated produces
can be readily excreted via kidney
can some drugs go directly to phase 2
yes
