Pharmacokinetics

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Pharmacokinetics

• objective is to describe time vs plasma
  concentration profile of a drug
• evaluate performance of different dosage forms
• adjust dosage regimens
• ADME processes modeled by viewing body as a
  series of interconnected compartments

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open one-compartment model

• process of distribution to each compartment is
  much faster than absorption into blood and
  elimination
• drug concentration everywhere in the compartment
  is equal (CSTR)
• elimination processes are pseudo-1st order

Vd
ka
Du
kel
D
DB
Cp
Dm
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IV injection
mass balance
log Cp
time, t
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Extravascular

• tablets, capsules, transdermal...
• most drugs absorbed by simple diffusion

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Continuous infusion
Cp
time
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• biological half-life
• time required to reduce amount of drug in body to
  1/2 original dose
• used to determine
• fluctuation of plasma concentration between doses
• persistence of drug in system once drug
  administration ceases

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Dosing Schedule
Cp
time after administration