Unit 1 - Pharmokinetics Flashcards Preview

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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

what will a decrease in clearance do?

increase t 1/2
-this can happen if there is renal or hepatic failure