Changing Drug Regimes

Question 1

Factors affecting drug absorption

Answer 1

• Related to drugs:
  ○ High for lipid soluble drugs
  ○ Low for Molecular size >1000 (large)
  ○ Increases for small particle size
  ○ Decreases for high degree of ionisation
  ○ Formulation can improve absorption
• Related to the body:
  ○ Increases with surface area of absorptive surface
  ○ pH will affect extent of ionisation
  ○ GI motility
  Slow - increases absorption
  Fast - decreases
  ○ Integrity of absorptive surface
  ○ Diseases

Question 2

Factors affecting drug distribution

Answer 2

• Related to drugs:
  ○ High for lipid soluble drugs
  ○ High for weak base drugs
  ○ Low for water soluble drugs
  ○ Low for weak acid drugs
• Related to body:
  ○ Increases with high body fat content for lipid soluble drugs
  ○ Increases with high body water content for water soluble drugs
  ○ Low for drugs highly bound to plasma proteins