Compartment model (single compartment)

[SH4:p5]

Central compartment contains

• Intravascular fluid
• Highly perfused tissues
  * including lungs, heart (5%), brain (15%), kidney (24%), and liver (28-30%)

Intercompartmental transfer may be decreased in elderly even with same dosage and Vd

Assumptions

• All drugs are eliminated from central compartment
  --> False
  * e.g. atracurium and cisatracurium are eliminated differently (via Hoffman elimination and ester hydrolysis)
• Pharmacological effects of a drug parallels its plasma concentration
  --> False
  * e.g. cisatracurium plasma concentration is falling after 1 min, but effect is increasing

NB:

• Elimination half-time is only useful in single compartment model, but not in multicompartmental models.