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Pk lab 5
1. Biopharmaceutics and
PK
Lab 5
Calculation of PK parameters using
one and two compartment model: IV
bolus.
Dr Sameh Rabea
2. Remember
For 1st order kinetic one-compartment the
equation will be:
Cp= (Cp) 0 e –kt
Where: Cp: Y ; (Cp) 0 : intercept; t: X; k: -slope x
2.303; Slope= (logC2 – logC1)/t2-t1.
Or Ke = ln (C1/C2)/t2-t1
The PK model:
I.V. Central Ke
injection Compartment Out.
AUC= Cp0/ Ke
Vdc= Dose/ Cp0.
t ½= 0.693/ Ke.
3. For 1storder kinetic two-compartment
the equation will be:
Cp= A e –αt + B e –βt
Where A: intercept of line 1 and B
intercept of line 2; α: distribution
rate constant and β: elimination rate
constant.
4. The PK model:
I.V.
in Central
K12
Peripheral
Compartment Compartment
inj.
K 21
K2
Cp0= A + B
K2 = Cp0 / ( A/ α + B/ β )
K12= A.B (β- α) 2 / Cp0 (A β + B α)
K21= A β + B α / Cp0 .
5. AUC= A/α + B/β .
t ½= 0.693/ β.
Vd c= Dose/Cp0= Dose/ A+B.
Vd area= Dose/AUC. β
Vd ss = Vdc + (K12/K21) Vdc
Vd tissue= Vd area – Vdc.
Therefore: Vd area> Vd ss > Vdc> Vd tissue.
But Vd ss is not affected by elimination, so its
represents true volume of distribution.
CL = Vdc. Ke or CL= Vdc. Β.
6. Problem # 1
A patient received 500 mg cefepime I.V
bolus injection and numerous blood
samples were drawn as the following:
8. A- Test the order of this data.
B- Write your model
Calculate as many PK parameter as
possible.
9. Problem # 2
A patient received 300 mg I.V.
dose of a drug. Several blood
samples were collected and the
following plasma concentrations
were obtained:
11. Test the order of this data.
Write the model.
Calculate PK parameters.
12. Problem # 3
A patient received 350 mg I.V
bolus dose of drug. Several
blood samples were collected
and the following plasma
concentrations were obtained: