Pharmacokinetcs 2

Question 1

What is the scatchard plot ? And what are the conditions for it

Answer 1

When the drug protein complex, DP is in equilibrium with free drug and protein, [DP]# [D]+[P] where # is the reversible equilibrium sign

Scatchard plot: (r/[D]= 1/Kd - r/Kd)

Question 2

What is Vd and how is it calculated

Answer 2

Apparent volume of distribution, a parameter which indicated extent of distribution, it can be estimated from the equation:

Vd= dose/Cp^0
Where Cp^0 is the concentration which would be achieved after equilibrium in the absence of any drug elimination

A drug which is confined to the extracellular space will have a smaller Vd than one which penetrates total body water