# Drug Disposition III Flashcards

Important pharmacokinetic parameters: (5)

Bioavailability

Volume of distribution

First order elimination rate constant

Half-life

Clearance

During time course of drug action, assume ____ concentrations are proportional concentrations at _____ tissue.

plasma

target

Drug action models are especially useful when: (2)

- when magnitude of therapeutic effect cannot be measured clinically
- therapeutic window is narrow

Pharmacokinetic parameters vary substantially in the population and can even change over time in a single patient. True or false?

true

Most drugs are eliminated this way:

first order drug elimination

Constant fraction of drug eliminated per unit time is ___ ____ drug elimination.

first order

The first order elimination rate constant, ____ is the fractional rate of drug elimination.

k_{E}

What are the units for k_{E}?

units of reciprocal time

How do you calculate k_{E} given starting plasma concentration?

For example, starting plasma concentration is 600 ng/ml.

starting plasma concentration * (1-k_{E})

480 ng/ml

The time required to reduce the plasma drug concentration by 50% is known as _____.

What are the units?

half-life

time

t_{1/2} is _________ proportional to k_{E}.

inversely

Estimate the half life of the drug:

50% of y-axis, then 1/2 on x-axis in left direction and half in right direction.

Subtract x(greater value) - x(lesser value) = seconds

about 0.7

Calculate half life from Log Plasma Concentration versus time plot

t_{1/2 =}

-0.301/1

What determines duration of action of a single dose?

half-life

___-___ half-lives for a dose to be effectively eliminated

5-6

In ______ dosage schedules, determines time to reach a new steady state when rate of administration changes.

chronic

Together, half life with _____ __ _____, determines choice of dosage interval.

margin of safety

Half life is an _____ process.

exponential

Drug administration is ____ order and elimination is ____ order.

zero

first

Because taking the pill does not depend on plasma concentrations.