1. CHAPTER 4
INTRAVENOUS INFUSION

2. ONE COMPARTMENT MODEL WITH IV INFUSION
This can be obtained by high degree of precision by infusing drugs i.v. via a drip or pump in hospitals

3. PK of Drug Given by IV Infusion
Zero-order Input (infusion rate, R)
First-order Output (elimination)

4. Integrated equation Zero-order Input (infusion rate, R)
First-order Output (elimination)
By integration,

5. Stopping the infusion before reaching steady state
Infusion stops

6. Stopping the Infusion
Equations

7. Steady State Concentration
IV Infusion until reaching Css

8. Steady State Concentration (Css)
Theoretical SS is only reached after an infinite infusion time
Rate of elimination = kel Cp

9. Steady State Concentration (Css)
Rate of Infusion = Rate of Elimination
 The infusion rate (R) is fixed while the
rate of elimination steadily increases
 The time to reach SS is directly
proportional to the half-life
 After one half-life, the Cp is 50% of the CSS, after 2 half-lives, Cp is 75% of the Css …….

10. Steady State Concentration (Css)
In clinical practice, the SS is considered to be reached after five half-lives

11. Increasing the Infusion Rate
If a drug is given at a more rapid infusion rate, a higher SS drug concentration is obtained but the time to reach SS is the same.

12. Loading Dose plus IV Infusion
DL with IV infusion at the same time
Loading dose
IV infusion
DL + IV infusion

13. Loading Dose plus IV Infusion
DL is used to reach SS rapidly

14. Reaching SS Immediately
Let , DL = CssVd But, CssVd = R / kel
Therefore, if a DL = R / kel is given SS will be reached immediately
but

15. Reaching SS Immediately
IV DL equal to R /kel is given, followed by IV infusion at a rate R

16. DL + IV Infusion