Exam 3: IV Dosing

Question 1

Importance of Pharmacokinetics

Answer 1

• Drug concentration does not reach toxic levels
• Drug concentration is in the therapeutic range
• The duration of effect leads to practical dosing

Question 2

Importance of half life

Answer 2

After 1 half life, 50% of the drug is eliminated
After 2 half lives, 75% of the drug is eliminated
After 3 half lives, 87.5% of the drug is eliminated

And so on-> keeps decreases by 1/2

Question 3

Fraction remaining formula

Answer 3

(1/2) ^x

Question 4

IV Bolus uses what order elimination

Whats the eqaution?

Answer 4

1st order

Ct = C0 * e^-kt

Taking the ln of equation makes it linear

Question 5

What ADME processes help with elimination

Answer 5

Metabolism and Excretion

Elimination processes begin immediately

Question 6

Drug infusions

Answer 6

In an infusion, the plasma concentration won’t reach therapeutic range immediately

• We are introducing the drug gradually into
  the circulation

Question 7

Loading dose

Answer 7

Bolus dose needed to immediately yield a

plasma concentration of drug in the therapeutic range

Question 8

Maintenance dose

Answer 8

Infused dose needed to maintain a plasma

concentration of drug in the therapeutic range

Question 9

When a drug is being administered it is->

Answer 9

simultaneously being eliminated

Question 10

Starting an infusion

Answer 10

• Rate of administration>Rate of elimination

* Drug accumulates in the plasma

Question 11

At Steady state

Answer 11

Rate of administration=Rate of elimination

The plasma drug concentration doesn’t change

Question 12

How many half lives does it take to reach steady state?

Answer 12

5

Question 13

Multiple doses - IV bolus

Answer 13

Usually, more than a single dose is needed

- In the graph, concentration of drug goes up and down

Question 14

Peak concentration

Answer 14

The high concentration following a dose is known as the peak concentration

Known as Cmax

Question 15

Trough concentration

Answer 15

The low concentration following a dose is known as the trough concentration

Known as Cmin

Question 16

Intermittent Dosing

Answer 16

Repeated administration of bolus dose
- single dose usually given over <5 min

-Peak concentration reached rapidly
- Elimination reduces plasma drug levels
• Trough concentrations may be below the
MEC

Question 17

Sub-therapeutic

Answer 17

area below the MEC

Question 18

Goal of dosing

Answer 18

maintain plasma conc. within therapeutic window

Question 19

Dosing interval τ

Answer 19

time that elapses between doses

Question 20

C0 is the

Answer 20

• initial plasma conc.
• also peak conc.
• = to Cmax

Question 21

Ct

Answer 21

concentration after time t

• conc. of drug just before the next dose
• also trough conc.
• = Cmin

Question 22

t in equation represents

Answer 22

the time that elapses

Question 23

τ

Answer 23

the time interval between dose n and dose n+1

Question 24

t1/2= τ and t1/2 > τ

Answer 24

drug accumulates

Question 25

If our half life is long relative to τ, then

Answer 25

drug can accumulate in the plasma

Question 26

If 5*t1/2 >τ

Answer 26

Drug doesn’t accumulate in plasma

Question 27

Calculating Drug Accumulation

Answer 27

The concentration remaining after the 1st dose is additive with the concentration of the second dose

Question 28

Loading Dose

Answer 28

• Initial higher dose given to rapidly yield a plasma concentration of drug in the
therapeutic range

CP = Desired peak [Drug]

Question 29

IV Infusion – Rate of administration

When starting an IV dose,

Answer 29

the drug concentration in the plasma is zero

Question 30

As drug administration starts->

Answer 30

the plasma drug concentration increases

Question 31

In IV infusion, the rate of administration (Ra)

Answer 31

is greater than the rate of elimination (Re)

• drug accumulates

Ra > Re

Question 32

Rate of administration is

Answer 32

how much we introduce per unit time

- Ra

Question 33

Rate of administration formula

Answer 33

dose (mg) / time (hr)

Question 34

Administration process occurs by

Answer 34

zero-order kinetic

Question 35

Elimination process occurs by

Answer 35

first-order kinetic

Question 36

Change in drug concentration

Answer 36

rate of elimination - rate of administration

Question 37

When the rate of administration exceeds the rate of elimination ->

Answer 37

the rate of change of drug concentration is the difference between these rates

Question 38

The rate of elimination is dependent on

Answer 38

the clearance and the plasma drug conc.

Question 39

Rate of elimination equation

Answer 39

Re = Cl * Conc.

Question 40

Clearance equation

Answer 40

Cl= Ke *Vd

Question 41

Steady state

Answer 41

the rate of drug going in is equal to the rate of drug going out

rate of administration = rate of elimination

Question 42

rate of administration formula

Answer 42

dose/t

Question 43

rate of elimination fromula

Answer 43

[C]ss*Cl

Question 44

What Happens Before Steady State

Answer 44

The concentration initially rises with time
• As time increases, we start to see the concentration plateau off
• The plateau concentration is that at steady state (Css)

Question 45

What Happens Before Steady State

Answer 45

The concentration at time t (Ct) is less than that at steady state (Css)

Question 46

To calculate Ct , we use the following equation

Answer 46

• Ct =Css*(1-e^-kt)

Question 47

As time increases, (1-e-kt) approaches

Answer 47

1

Question 48

Conc. at steady state formula

Answer 48

[C]ss =(dose/t)/ Cl