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DRUG METABOLISM - Coggle Diagram

- - - - e.g; persistent CNS effect of diazepam can be partly attributed to one of its major metabolite desmethyldiazepam
  - - - activity of microsomal enzymes can be induced by many drugs with resultant acceleration of biotransformation rates
    - - inhibition can occur with microsomal and non-microsomal enzyme, resulting in decreased biotransformation rates
  - - - SLOW ACETYLATORS
        parent drug itself is toxic
        e.g. isoniazid- induce polyneuritis
      - FAST ACETYLATORS (80% among eskimos, plynesians and asians, low among Mediterranean Jews)
        acetylated metabolite is toxic
        e.g; hepatitis induced by acetylhydrazine formed from isoniazid
  - - - drug metabolizing capacity < adults
        
        "grey baby syndrome" produced by cloramphenicol
        -inability to metabolise antibiotic by glucuronidation due to deficiency of UDP-glucoronyl transferase
    - - drug metabolise capacity > adult
        
        faster clearance of iv theophyline than adults
    - - decrease rate of metabolism
        
        affect oxidative reactions
        not affect conjugation
- - - - reactions include:
        -oxidation
        -reduction
        -hydrolysis
      - occur in sER (microsomal 'mixed function oxidase' system)
        -also called monooxygenases, cP450 system
      - metabolites:
        -excreted in urine/ undergo phase II reactions (if still too lipophilic)
      - reactive/ even toxic
  - - - reaction include:
        -glucoronidation (most common)
        -conjugation with sulphate
        -conjugation with gluthathione
        -amino acid conjugation
        -acetylation
        -methylation
      - occur mainly in cytosol (except UGT which are microsomal)
      - metabolites:
        -more polar
        -can be excreted in kidney and bile
        -almost always inactive except morphine 6-glucuronide