Flashcards in Unit 1 - Pharmokinetics Deck (14):

1

## explain kinetic compartments

### compartments are the fluid space containing the drug, which is useful for mathematical calculations

2

## what determines the elemination constant (Ke) of a drug?

### a rate limiting step

3

## what is significant about the "peak" of a single dose therapy?

### the absorption = elimination

4

## explain absorption kinetics

### absorption rates are related to transport processes involved, either zero or first order

5

##
explain zero order rate of absorption

-what is the equation for concentration of a drug in Vd after a certain time?

-what does it look like on a graph?

-what are 2 examples?

###
carrier mediated with saturated carrier protein at Vmax; not sensitive to drugs

-Ct = Ka*t --> amount per time (straight line on normal graph)

--Ka might be fast or slow, but it is always constant

-examples are IV infusions and transcutaneous patches (both have constant rates of delivery)

6

##
explain first order rate of absorption

-what is the equation for concentration of a drug in Vd after a certain time?

-what does it look like on a graph?

-what is an example?

###
proportional to the amount of drug present; sensitive to drug concentration

-Ct = M / Vd * (1 - e^-Ka*t) --> proportion per time (hyperbole on normal graph)

--with time, we approach a max amount absorbed that hopefully equals most of the dose

--the larger the dose, the faster the concentration rises in the compartment

-example is oral

7

## what 4 things does pharmocokinetics determine?

###
1. how Often to Dose a Drug

2. What Size Dose to Give

3. How Long to Expect a Dose to Last

4. When to Re-dose a Drug to Sustain the Effect

8

## is elimination dependent or independent of drug concentration? what does the rate limiting step need?

###
independent of drug concentration, and rate limiting step must be:

1. insensitive to drug concentration

2. saturated

9

## explain zero order elimination, its equation, and what it looks like on a graph

###
an amount per unit time

Ct = Ci - Ke*t

-looks like a straight negative slope (slope - -Ke) on a normal graph

10

## explain first order elimination, its equation, and what it looks like on a graph

###
a proportion per unit time

log Ct = log Ci - (Ke * t)/2.303

-normal axis is negative hyperbole, log axis is negative straight line

11

##
which order is it if:

Ct << Km

Ct >> Km

###
when Ct << Km, v = k * Ct --> first order rate

when Ct >> Km, v = Vm --> zero order rate (constant in that system

12

## what is the formula for half life of a drug in plasma when it's first order elimination?

###
t 1/2 = 0.693 / Ke

-thus, t 1/2 is constant

13

## what is the relationship between Vd, Cl, and t 1/2?

###
Cl = Vd * Ke

since t 1/2 = 0.693 / Ke

t 1/2 = (0.693 * Vd) / Cl

14