02- Dosing Regimens

Question 1

Toxic Range

Answer 1

range in which a certain plasma concentration of a drug produces toxicity

Question 2

Therapeutic Range

Answer 2

range in which a certain plasma concentration of a drug exhibits the desired therapeutics effects of the drug

Question 3

Ineffective Range

Answer 3

range in which the plasma concentration of a drug is too low to see any therapeutic effects of the drug
-not enough drug activating receptors to produce a response

Question 4

Minimum Effective Concentration (MEC)

Answer 4

the lowest plasma concentration of a drug that produces an observable response

Question 5

Css

Answer 5

average steady state plasma concentration

-usually desired within the therapeutic range

Question 6

Bioavailability (F)

Answer 6

fraction of drug reaching the systemic circulation in its active form
-IV has bioavailability of 1

Question 7

AUC

Answer 7

area under the curve, used to measure bioavailability of a drug?

Question 8

Onset of Action

Answer 8

how long it takes after administration of a drug to see the desired effects of the drug (how long does it take plasma concentration to reach MEC)

Question 9

Duration of Action

Answer 9

how long plasma concentration of a drug stays above MEC

-measured from onset of action to end of action

Question 10

Apparent Efficacy

Answer 10

the efficacy that is seen in the patient and is variable from person to person
-reflective of the peak plasma concentration achieved by certain drug dose and its observed effect

Question 11

Rate of Availability

Answer 11

rate at which drug enters systemic circulation

-affects onset of action and can affect apparent efficacy and duration of action

Question 12

Volume of Distribution (Vd)

Answer 12

the apparent volume in which a drug distributes

Vd= Amount of drug in body (bioavailability x administered dose)/plasma concentration (Cp)

Question 13

Clearance (CL)

Answer 13

elimination of active drug after its distribution
CL= Rate of elimination/Cp (plasma concentration)
-includes elimination by excretion and metabolism

Question 14

1st Order Elimination

Answer 14

delivery-limited elimination where capacity is not saturated so elimination is dependent on Cp

• percentage eliminated is constant but amount eliminated is variable
• CL is usually constant

Question 15

“0” Order Elimination

Answer 15

capacity-limited elimination where capacity is saturated and constant amount of drug eliminated per unit time (percentage eliminated variable)
-rate of elimination independent of Cp, and CL is variable

Question 16

Loading Dose- D(L)

Answer 16

dose given to quickly attain Css by filling Vd

• dose dependent on Vd which is proportional to body weight
• D(L)= (Css x Vd) / F

Question 17

Maintenance Dose- D(M)

Answer 17

dose given to maintain Css by replacing loss due to elimination
-dependent on elimination
D(M)= [(Css x CL) / F] x dosing interval
Rate of elimination= (Cp x CL)

Question 18

Dosing Frequency (interval)

Answer 18

interval in which a certain dose of drug is given to maintain Css in therapeutic range
-dependent on clearance (CL) which relates to drug half-life (t1/2)

Question 19

Drug Half-Life (t1/2)

Answer 19

time required for plasma concentration of drug to decrease by half
t1/2= (0.693 x Vd) / CL

Question 20

Target Effect Strategy

Answer 20

dosing strategy is which a drug dose is titrated to achieve a desired therapeutic effect in a patient
-use effect that you see in the patient to decide whether to increase or decrease a given drug dose

Question 21

Target Concentration Strategy

Answer 21

dosing strategy in which a drug dose is titrated to achieve a specific plasma concentration
-used when an effect cannot be readily determined or with a drug that has a low T.I.

Question 22

Maximal Dose Strategy

Answer 22

dosing strategy in which highest allowed dose is initially given
-used with drugs that have a high T.I.

Question 23

Plateau Effect

Answer 23

the effect normally seen after administering 4 to 5 half-life doses in which further administration of half-life doses does not cause an increase in the Css

Question 24

Cp(0)

Answer 24

apparent plasma concentration at time 0

• used to determine Vd
• can only be observed mathematically because requires instantaneous absorption and distribution, and no metabolism