Drug Metabolism Flashcards
what is drug metabolism?
the enzymatic conversion of a drug to another chemical entity
what is the most important organ in drug metabolism?
the liver
what other organs are involved in drug metabolism?
kidney
gut mucosa
lungs
skin
what effect does hepatic metabolism have on drugs administered orally?
reduces their bioavailability
what are the phases of drug metabolism?
phase I
phase II
what are the hepatic drug metabolising enzymes called?
microsomal enzymes
where are microsomal enzymes located?
embedded in the SER of liver hepatocytes
which type of molecule is metabolised more readily - polar or non-polar?
non polar, cross the plasma membrane more easily
what are phase I reactions?
a change in the drug by oxidation, reduction or hydrolysis
how is oxidation of a drug accomplished?
by cytochrome P450 enzymes
what happens to a drug during oxidation?
incorporates an atom of oxygen to form a hydroxyl group
what type of bonds are susceptible to phase I hydrolysis reactions?
ester
amide
what do phase I reactions usually form?
chemically reactive metabolites
can be pharmacologically active and/or toxic
what are cytochrome P450 enzymes?
haem proteins
what do phase II reactions involve?
combining the drug with a polar molecule to form a water soluble metabolite
