Drug metabolism

Drug metabolism may have the following effects:

• prodrugs activated:
  • improved absorption
  • improved distribution - L-dopa vs dopamine
  • avoiding adverse effect in gut
• active drug converted to other active compounds:
  • diamorphine to morphine
  • diazepam to desmethyliazepam
  • lignocaine to toxic metabolites
  • procainamide to n-acetylprocainamide - less toxic
• active drugs inactivated:
  • phase I - oxidation, reduction, hydrolysis,
  • phase II - conjugation - sulphatation, glucuronidation, methylation etc.
    
    
• factors which may alter metabolism include:
  • genetic
  • drugs
  • hepatic blood flow
  • liver disease - must be severe, but shunting is powerful
  • age - reduced metabolic capacity in young and elderly