B SYL2017: Describe how pharmacokinetics are affected by ageing


  • Reduced cognitive fn & compliance


  • Decreased BF to soft tissue & gut
  • Changes in gastric pH
  • Reduced SA for gas xchg

Overall → reduced absorptive capacity of drugs from any route


  • Reduced CO = increase arm-to-brain time for IV administration
  • Vd alterations:
    • Reduced sk m
    • Increase fat stores
    • Reduced PPB
    • Reduced ECF/ICF

= Increased availability of high PPB drugs

= Increased accumulation of fat soluble drugs & higher CSHT


  • Reduced hepatic enzymatic capacity & hepatic BF
    • Reduced 1st pass metabolism
    • Reduction in metabolism of drugs (either for activation of prodrugs/inactivation of drugs)
    • Increased risk hepatotoxicity


  • Reduction in renal fn
    • Reduced ability to clear hydrophilic drugs
    • Reduced drug excretion overall
    • Dangerous for drugs w narrow therapeutic window (Lithium, aminoglycosides, digoxin)

Drug Interactions

  • At high risk, more likely to have multiple doctors & multiple prescriptions