Pharmacokinetics: Clinical Applications (Pilch) - 081016

Question 1

What are the two major patterns by which drugs are administered?

Answer 1

1. Continuous administration at a constant rate (IV infusion)
2. Discontinuous administration - patient takes chronic repeated doses at specific intervals (i.e. oral administration of pills)

Question 2

Continuous Drug Regimen or IV infusion

Explain Rate of Entry vs. Rate of Loss

Answer 2

INPUT: Rate of Entry (Rzero, mL/min) - constant w/ time… absorption follows zero-order kinetics

OUTPUT: Rate of Loss - first order kinetics, does change with time and it depends on the concentration

Output = total body clearance (kd x Vd) * plasma concentration (Cpl) of drug at that instant

Upon starting IV infusion, plasma conc. rises until rate of loss equals rate of input –> Css plasma concentration reached