multi-compartment models and apparent volume of distribution

what is apparent volume of distribution?

• numeric value may be similar to a physiological space in the body

• does not encessarily correspond to a physiological volume

• can be used for calculating dose

what is 1CM?

• C(0) can be determined by back extrapolation

what is protein binding?

drug + protein ↔ drug-protein complex

• acidic drugs commonly bind to albumin
• basic drugs often bind to alpha1-acid glycoprotein

what is the extent of distribution?

• Vd increases when f_u,p is increased

• Vd decreases when f_u,t is increased

• f_u,t: average value across all tissues into which drug distributes

• Kp can vary considerably among tissues

what is V_area, V_β, and V_Z?

• volume calculated at the terminal elimination phase
• uses area under the concentration-time curve
• influenced by changes in clearance

what is V_area after EV administration?

the dose that gains access to the systemic circulation might be less than 100%

what is the relationship between various Vd for multicompartment systems?

• V_area > V_SS > V_c
• Vd is time-dependent during the distribution phase
• bi-exponential equation